doc/texinfo.texi

\input texinfo.tex    @c -*-texinfo-*-

@setfilename texinfo.info

@c Automake automatically updates version.texi to @set VERSION and
@c @set UPDATED to appropriate values.
@include version.texi
@settitle GNU Texinfo @value{VERSION}

@c Define a new index for command-line options.
@defcodeindex op

@c Put everything except function (command, in this case) names in one
@c index (arbitrarily chosen to be the concept index).
@syncodeindex op cp
@syncodeindex pg cp

@c finalout

@c flag to index command names without extra text in the entry
@ifinfo
@set commandlookup
@end ifinfo
@ifhtml
@set commandlookup
@end ifhtml

@microtype on

@copying
This manual is for GNU Texinfo (version @value{VERSION}, @value{UPDATED}),
a documentation system that can produce both online information and a
printed manual from a single source using semantic markup.

Copyright @copyright{} 1988-2026 Free Software Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts.  A copy of the license is included in the section entitled
``GNU Free Documentation License''.
@end quotation
@end copying

@documentinfo
@title Texinfo
@subtitle The GNU Documentation Format
@subtitle for Texinfo version @value{VERSION}, @value{UPDATED}

@author Robert J. Chassell
@author Richard M. Stallman
@end documentinfo

@publication
Published by the Free Software Foundation @*
31 Milk St # 960789 @*
Boston, MA 02196 @*
USA @*
ISBN 1-882114-67-1 @c for version 4.0, September 1999.
@c ISBN 1-882114-65-5 is for version 3.12, March 1998.
@c ISBN 1-882114-64-7 is for edition 2.24 of November 1996.
@c ISBN 1-882114-63-9 is for edition 2.20 of 28 February 1995.

@ignore
@sp 1
Cover art by Etienne Suvasa.
@end ignore
@end publication

@maketitle

@dircategory Texinfo documentation system
@direntry
* Texinfo: (texinfo).           The GNU documentation format.
* install-info: (texinfo)Invoking install-info. Update info/dir entries.
* texi2any: (texinfo)Invoking texi2any.         Translate Texinfo source.
* makeinfo: (texinfo)Invoking texi2any.         Translate Texinfo source.
* pod2texi: (texinfo)Invoking pod2texi.         Translate Perl Pod to Texinfo.
* texi2dvi: (texinfo)Format with texi2dvi.      Print Texinfo documents.
* texi2pdf: (texinfo)PDF Output.                PDF output for Texinfo.
* pdftexi2dvi: (texinfo)PDF Output.             PDF output for Texinfo.
* texindex: (texinfo)Format with tex/texindex.  Sort Texinfo index files.
@end direntry

@set txiindexatsignignore
@set txiindexbackslashignore
@set txiindexlessthanignore
@set txiindexhyphenignore


@summarycontents
@contents


@node Top
@top Texinfo

This manual is for GNU Texinfo (version @value{VERSION}, @value{UPDATED}),
a documentation system that can produce both online information and a
printed manual from a single source using semantic markup.

@ifinfo
The first part of this master menu lists the major nodes in this Info
document, including the @@-command and concept indices.  The rest of
the menu lists all the lower-level nodes in the document.
@end ifinfo


@node Copying Conditions
@nodedescription Your rights.
@unnumbered Texinfo Copying Conditions
@cindex Copying conditions
@cindex Conditions for copying Texinfo
@cindex Free software
@cindex Libre software

GNU Texinfo is @dfn{free software}; this means that everyone is free
to use it and free to redistribute it on certain conditions.  Texinfo
is not in the public domain; it is copyrighted and there are
restrictions on its distribution, but these restrictions are designed
to permit everything that a good cooperating citizen would want to do.
What is not allowed is to try to prevent others from further sharing
any version of Texinfo that they might get from you.

Specifically, we want to make sure that you have the right to give away
copies of the programs that relate to Texinfo, that you receive source
code or else can get it if you want it, that you can change these
programs or use pieces of them in new free programs, and that you know
you can do these things.

To make sure that everyone has such rights, we have to forbid you to
deprive anyone else of these rights.  For example, if you distribute
copies of the Texinfo related programs, you must give the recipients all
the rights that you have.  You must make sure that they, too, receive or
can get the source code.  And you must tell them their rights.

Also, for our own protection, we must make certain that everyone finds
out that there is no warranty for the programs that relate to Texinfo.
If these programs are modified by someone else and passed on, we want
their recipients to know that what they have is not what we distributed,
so that any problems introduced by others will not reflect on our
reputation.

The precise conditions of the licenses for the programs currently
being distributed that relate to Texinfo are found in the General
Public Licenses that accompany them.  This manual is covered by the
GNU Free Documentation License (@pxref{GNU Free Documentation
License}).


@node Overview
@nodedescription Texinfo in brief.
@chapter Overview of Texinfo
@cindex Overview of Texinfo
@cindex Texinfo overview
@cindex Using Texinfo in general
@cindex Texinfo, introduction to
@cindex Introduction to Texinfo
@anchor{Using Texinfo} @c merged node

@dfn{Texinfo} is a documentation system that uses a single source file
to produce both online information and printed output.  This means
that instead of writing several different documents, one for each output 
format, you need only write one document.

Using Texinfo, you can create a printed document (via the @TeX{}
typesetting system) in PDF format, including chapters,
sections, cross-references, and indices.  From the same Texinfo source
file, you can create HTML output suitable for use with a web
browser, you can create an Info file for use in GNU Emacs or other
Info-reading programs, and also create DocBook, EPUB 3, or @LaTeX{} files.

@cindex Source file format
@cindex Semantic markup
A Texinfo source file is a plain text file containing text interspersed
with @dfn{@@-commands} (words preceded by an @samp{@@}) that tell the
Texinfo processors what to do.  Texinfo's markup commands are almost 
entirely @dfn{semantic}; that is, they specify the intended meaning
of text in the document, rather than physical formatting instructions.

Output to most output formats is handled by the @command{texi2any}
program.  @xref{Generic Translator @command{texi2any}}.
The exception is when Texinfo code is processed by @TeX{} to DVI or
PDF (@pxref{Printed Books}, below).
Emacs also offers commands for converting Texinfo code to Info
(@pxref{@code{texinfo-format} commands}).

GNU Emacs has a special mode, called Texinfo mode, that provides various
Texinfo-related features. (@xref{Texinfo Mode}.)

@cindex Limited scope of Texinfo
Texinfo was devised specifically for the purpose of writing software
documentation and manuals.  If you want to write a good manual for
your program, Texinfo has many features which we hope will make your
job easier.  However, Texinfo is not intended to be a general-purpose
formatting program.  It provides almost no commands for controlling
the final formatting, so may be inappropriate for your needs if you
want to lay out a newspaper, devise a glossy magazine ad, or follow
the exact formatting requirements of a publishing house.

@cindex Spelling of Texinfo
@cindex Pronunciation of Texinfo
Spell ``Texinfo'' with a capital ``T'' and the other letters in
lowercase.  The first syllable of ``Texinfo'' is pronounced like
``speck'', not ``hex''.  This odd pronunciation is derived from the
pronunciation of @TeX{}.  Pronounce @TeX{} as if the @samp{X} were
the last sound in the name `Bach'.  In the word @TeX{}, the @samp{X}
is, rather than the English letter ``ex'', actually the Greek letter
``chi''.

Texinfo is the official documentation format of the GNU project.
More information, including manuals for GNU packages, is available
at the @uref{https://www.gnu.org/doc/, GNU documentation web page}.


@node Reporting Bugs
@nodedescription Submitting effective bug reports.
@section Reporting Bugs

@cindex Bugs, reporting
@cindex Suggestions for Texinfo, making
@cindex Reporting bugs
We welcome bug reports and suggestions for any aspect of the Texinfo
system: programs, documentation, installation, etc.  Please email them
to @email{bug-texinfo@@gnu.org}.  You can get the latest version of
Texinfo via its home page, @uref{https://www.gnu.org/software/texinfo}.

@cindex Checklist for bug reports
For bug reports, please include enough information for the maintainers
to reproduce the problem.  Generally speaking, that means:

@itemize @bullet
@item The version number of Texinfo and the program(s) or manual(s) involved.
@item The contents of any input files necessary to reproduce the bug.
@item Precisely how you ran any program(s) involved.
@item A description of the problem and samples of any erroneous output.
@item Hardware and operating system names and versions.
@item Anything else that you think would be helpful.
@end itemize

When in doubt whether something is needed or not, include it.  It's
better to include too much than to leave out something important.

It is critical to send an actual input file that reproduces the
problem.

Any problems with the Info reader in Emacs should be reported to
the Emacs developers: see @ref{Bugs,,, emacs, The GNU Emacs Manual}.

@cindex Patches, contributing
Patches are welcome; if possible, please make them with @samp{@w{diff -c}},
@samp{@w{diff -u}} (@pxref{,,, diffutils, Comparing and Merging Files}),
or @samp{git diff} and include @file{ChangeLog} entries (@pxref{Change Logs,,,
standards, GNU Coding Standards}), and follow the existing coding style.


@node Output Formats
@nodedescription Overview of the supported output formats.
@section Output Formats
@cindex Output formats
@cindex Back-end output formats

Here is an overview of the output formats currently supported by Texinfo.

@table @asis
@cindex Info output, overview
@item Info
(Generated via @command{texi2any}.)  Info format is mostly a plain
text transliteration of the Texinfo source.  It adds a few control
characters to provide navigational information for cross-references, 
indices, and so on.  The Emacs Info subsystem (@pxref{Top,,, info, 
Info}), and the standalone @command{info} program (@pxref{Top,,, 
info-stnd, GNU Info}), among others, can read these files.  @xref{Info 
Files}, and @ref{Creating and Installing Info Files}.

@cindex Plain text output, overview
@item Plain text
(Generated via @command{texi2any --plaintext}.)  This is almost the
same as Info output with the navigational control characters
omitted.

@cindex HTML output @subentry overview
@item HTML
@c @cindex Mozilla
@c @cindex Lynx
@c @cindex Emacs-W3
(Generated via @command{texi2any --html}.)  HTML, standing for Hyper
Text Markup Language, is the language for writing documents on the World
Wide Web.  Web browsers
@c such as Mozilla, Lynx, and Emacs-W3
can render this language online.  There
are many versions of HTML, both different standards and
browser-specific variations.  @command{texi2any} uses a subset
of the language that can be interpreted by any common browser,
intentionally not using many newer or less widely-supported tags.
Although the native output is thus rather plain, it can be customized
at various levels, if desired.   @xref{Generating HTML}.

@cindex EPUB 3 output, overview
@item EPUB 3
(Generated via @command{texi2any --epub3}.)
EPUB is a format designed for reading electronic books on
portable devices.  It is a derivative of HTML@.  The format was
developed by the International Digital Publishing Forum (IDPF),
which is now part of the World Wide Web Consortium (W3C)@.  The
latest major revision, EPUB 3, dates from 2011.


@cindex DVI output, overview
@pindex dvips @r{(program)}
@pindex xdvi
@item DVI
(Generated via @command{texi2dvi}.)  The DeVIce Independent binary
format is output by the @TeX{} typesetting program
(@uref{http://tug.org}).  This is then read by a DVI `driver', which
knows the actual device-specific commands that can be viewed or
printed, notably Dvips for translation to PostScript (@pxref{Top,,,
dvips, Dvips}) and Xdvi for viewing on an X display
(@uref{http://sourceforge.net/projects/xdvi/}).  @xref{Hardcopy
with @TeX{}}.  (Be aware that the Texinfo language is very different
from @TeX{}'s usual languages: plain @TeX{}, @LaTeX{}, Con@TeX{}t,
etc.)

@cindex PostScript output, overview
@item PostScript
(Generated via @command{texi2dvi --ps}.)  PostScript is a page
description language that became widely used around 1985 and is still
used today.  @uref{https://en.wikipedia.org/wiki/PostScript} gives a
basic description and more preferences.  By default, Texinfo uses the
@command{dvips} program to convert @TeX{}'s DVI output to PostScript.
@xref{Top,,, dvips, Dvips}.

@cindex PDF output, overview
@cindex Beebe, Nelson
@item PDF
(Generated via @command{texi2dvi --pdf} or @command{texi2pdf}.)  This
format was developed by Adobe Systems for portable document
interchange, based on their previous PostScript language.  It can
represent the exact appearance of a document, including fonts and
graphics, and supporting arbitrary scaling.  It is intended to be
platform-independent and easily viewable, among other design goals;
@uref{https://en.wikipedia.org/wiki/Portable_Document_Format} and
@uref{http://tug.org/TUGboat/tb22-3/tb72beebe-pdf.pdf} have some
background.  By default, Texinfo uses the @command{pdftex} program, an
extension of @TeX{}, to output PDF; see
@uref{http://tug.org/applications/pdftex}.  @xref{PDF Output}.

@cindex LaTeX output, overview
@item @LaTeX{}
(Generated via @command{texi2any --latex}.)  This is a typesetting
system built on top of @TeX{}.  It was originally released by
Leslie Lamport in 1984.  @LaTeX{} adds more definitions to those
of @TeX{} and has a wide range of packages built on it. @LaTeX{} is
ubiquitous in academic literature. The current version of @LaTeX{}
is under active development; more information is available online
at @uref{https://www.latex-project.org/}.

The @LaTeX{} output can be further processed into DVI, PostScript,
or PDF@.  In theory, the @LaTeX{} output should allow for much more
customizability of the output than would be possible with the plain
@TeX{} implementation of Texinfo.


@cindex DocBook output, overview
@cindex XML DocBook output, overview
@item DocBook
(Generated via @command{texi2any --docbook}.)  This is an XML-based
format, primarily for technical
documentation.  It therefore bears some resemblance, in broad
outline, to Texinfo.  See @uref{http://www.docbook.org}.  Various
converters from DocBook @emph{to} Texinfo have also been developed;
see the Texinfo web pages.
@end table


@node Info Files
@nodedescription What is an Info file?
@section Info Files
@cindex Info files

As mentioned above, Info format is mostly a plain text transliteration
of the Texinfo source, with the addition of a few control characters
to separate nodes and provide navigational information, so that
Info-reading programs can operate on it.

Info files are nearly always created by processing a Texinfo source
document.  @command{texi2any}, also known as @command{makeinfo}, is
the principal command that converts a Texinfo file into an Info file;
@pxref{Generic Translator @command{texi2any}}.

Generally, you enter an Info file through a node that by convention is
named `Top'.  This node normally contains just a brief summary of the
file's purpose, and a large menu through which the rest of the file is
reached.  From this node, you can either traverse the file
systematically by going from node to node, or you can go to a specific
node listed in the main menu, or you can search the index menus and then
go directly to the node that has the information you want.  Alternatively,
with the standalone Info program, you can specify specific menu items on
the command line (@pxref{Top,,, info, Info}).

If you want to read through an Info file in sequence, as if it were a
printed manual, you can hit @key{SPC} repeatedly, or you get the whole
file with the advanced Info command @kbd{g *}.  (@xref{Advanced,,
Advanced Info commands, info, Info}.)

The @file{dir} file in the @file{info} directory serves as the
departure point for the whole Info system.  From it, you can reach the
`Top' nodes of each of the documents in a complete Info system.

@cindex URI syntax for Info
If you wish to refer to an Info file via a URI, you can use the
(unofficial) syntax exemplified by the following.  This works with
Emacs/W3, for example:
@example
info:emacs#Dissociated%20Press
info:///usr/info/emacs#Dissociated%20Press
info://localhost/usr/info/emacs#Dissociated%20Press
@end example

The @command{info} program itself does not follow URIs of any kind.


@node Printed Books
@nodedescription Characteristics of a printed book or manual.
@section Printed Books
@cindex Printed book and manual characteristics
@cindex Manual characteristics, printed
@cindex Book characteristics, printed
@cindex Texinfo printed book characteristics
@cindex Characteristics, printed books or manuals

@cindex Knuth, Donald
A Texinfo file can be formatted and typeset as a printed book or
manual.  To do this, you need @TeX{}, a sophisticated typesetting
program written by Donald Knuth of Stanford University.  It is not part 
of the Texinfo distribution.

Texinfo provides a file @file{texinfo.tex} that contains the definitions
that @TeX{} uses when it typesets a Texinfo file.
You can get the latest version of @file{texinfo.tex} from
the Texinfo home page, @uref{https://www.gnu.org/software/texinfo/}.

A Texinfo-based book is similar to any other typeset, printed work: it
can have a title page, copyright page, table of contents, and preface,
as well as chapters, numbered or unnumbered sections and subsections,
page headers, cross-references, footnotes, and indices.

@TeX{} is very powerful and has a great many features.  However,
because a Texinfo file must be able to present information both on a
character-only terminal in Info form and in a typeset book, the
formatting commands that Texinfo supports are necessarily limited.

@xref{Hardcopy with @TeX{}}, for more information on processing a
manual with @TeX{}.


@node History
@nodedescription Acknowledgements, contributors and genesis.
@section History

@cindex Stallman, Richard M.
@cindex Chassell, Robert J.
@cindex Fox, Brian
@cindex Berry, Karl
@cindex Smith, Gavin
Richard M. Stallman invented the Texinfo format, wrote the initial
processors, and created Edition 1.0 of this manual.  Robert@tie{}J.
Chassell greatly revised and extended the manual, starting with
Edition 1.1.  Brian Fox was responsible for the standalone Texinfo
distribution until version 3.8.  Karl Berry continued maintenance
from Texinfo 3.8 (manual edition 2.22), and Gavin Smith has continued
maintenance since Texinfo 6.0.

@cindex History of Texinfo
@cindex Texinfo history
@subheading Beginnings

@cindex NLS
Richard Stallman included an on-line, hypertext help system called
Info in the original implementation of Emacs (in 1975/6).
Stallman had been inspired after seeing a presentation a couple of years
earlier on the ``NLS'' hypertext system of Douglas Engelbart.

@ignore
From rms@santafe.edu Sat Jan 23 03:41:05 1999
Status: RO
X-VM-v5-Data: ([nil nil nil nil nil nil nil nil nil]
        [nil nil nil nil nil nil nil nil nil nil nil nil "^Date:" nil nil nil ni
+l nil nil nil nil]
        nil)
Reply-to: rms@gnu.org
Content-Length: 331
Date: Sat, 23 Jan 1999 01:40:59 -0700 (MST)
From: Richard Stallman <rms@gnu.org>
To: bob@rattlesnake.com
CC: karl@cs.umb.edu, kama@hippo.fido.de, bug-texinfo@gnu.org
Subject: Re: Q: Some history questions

    People at MIT also developed a nifty on-line help format called Info.

That was me.  I developed Info as a sort of "poor man's hypertext"
after I saw a presentation on NLS (Englebart's hypertext system).  I
THINK this was in 1974, actually before Emacs, and that after
developing Emacs in 1975 I adapted Info to work with it.
@end ignore

@cindex Scribe
@cindex Reid, Brian
In another development, in the 1970's at CMU, Brian Reid developed
a program and format named Scribe to mark up documents for printing.
It used the @code{@@} character to introduce commands, as Texinfo does.
Much more consequentially, it strove to describe document contents
rather than formatting, an idea wholeheartedly adopted by Texinfo.

@cindex Bolio
@cindex Bo@TeX{}
Meanwhile, people at MIT developed another format called Bolio.
Richard Stallman (RMS) worked on converting Bolio to use @TeX{} as
its typesetting language, resulting in Bo@TeX{}.  The earliest Bo@TeX{}
version seems to have been 0.02 on October 31, 1984.

Bo@TeX{} could only be used as a markup language for documents to be
printed, not for online documents.  RMS combined Bo@TeX{} and Info
to create Texinfo, a mark-up language for text that is intended to
be read both online and as printed hard copy.

The original translator to create Info was written
(primarily by RMS and Bob Chassell) in Emacs Lisp, namely the
@code{texinfo-format-buffer} and other functions.  In the early 1990s,
Brian Fox reimplemented the conversion program in C, now called
@command{makeinfo}, as well as the standalone @command{info} program.

@subheading Reimplementing in Perl

@cindex Cons, Lionel
@cindex Dumas, Patrice
In 2012, the C @command{makeinfo} was itself replaced by a Perl
implementation generically called @command{texi2any}.  This version
was initially based on @command{texi2html}, an independent program originally
written by Lionel Cons, later with substantial work by many others.
The features needed to make @command{texi2html} a replacement for
@command{makeinfo} were implemented by Patrice Dumas.  That program, however,
was never released.

@cindex Tree representation of documents
@cindex Syntax tree representation of documents
@cindex Abstract syntax tree representation of documents
The current implementation (also written by Patrice Dumas) inherited the design
of customization and other features from @command{texi2html} (for more on
@command{texi2html} compatibility, @pxref{@command{texi2html}}).  However,
@command{texi2any} was a full reimplementation: unlike @command{texi2html},  it
constructs a tree-based representation of the input document for all back-ends
to work from.

The new Perl program was intended to have the following advantages over
the old C program:

@itemize @bullet
@item HTML customization.  Many GNU and other free software packages
had been happily using the HTML customization features in
@command{texi2html} for years.  Thus, in effect two independent
implementations of the Texinfo language had developed, and keeping
them in sync was not simple.  Adding the HTML customization possible
in @command{texi2html} to a C program would have been an
enormous effort at that time.

@item Unicode, and multilingual support generally, especially of east
Asian languages.  At that time, doing it in C would have been tantamount
to rewriting the entire program.

@item Additional back-ends.  The @command{makeinfo} code had become
convoluted to the point where adding a new back-end was quite complex,
requiring complex interactions with existing back-ends.  In contrast,
the new implementation provides a clean tree-based representation for
all back-ends to work from.  People had requested numerous different
back-ends (@LaTeX{}, the latest (X)HTML, @dots{}); this change made them
much more feasible to implement.

@cindex @command{texi2any}, as reference implementation
@cindex Reference implementation
@cindex Implementation, @command{texi2any} as reference
@anchor{Reference Implementation}@c
@item @command{texi2any} was intended to be a reference implementation
that defines parts of the language not fully specified by the manual,
and to provide a reference for command-line options for any other
program that might process Texinfo in the future.

@end itemize

@cindex Future of Texinfo implementations
At the time,
the new Perl program was much slower than the old C program.
Since then, the parser, part of the Info converter
and the HTML converter as a whole have been translated to C, leading to
important gains in speed compared to the pure Perl implementation of
@command{texi2any}.  The main program has also been translated to C.  The
@command{texi2any} C implementation embeds a Perl interpreter for the parts
that require Perl.


@node Adding Output Formats
@nodedescription Man pages and implementing new formats.
@section Adding Output Formats
@cindex Additional output formats

The output formats in the previous sections handle a wide variety of
usage, but of course there is always room for more.

@cindex Output formats, supporting more
If you are a programmer and would like to contribute to the GNU
project by implementing additional output formats for Texinfo, that
would be excellent.  The way to do this that would be most useful is
to write a new back-end for @command{texi2any}, our reference
implementation of a Texinfo parser; it creates a tree representation
of the Texinfo input that you can use for the conversion.  The
documentation in the source file
@file{tta/perl/Texinfo/Convert/Converter.pm} is a good place to start if you are
willing to develop in Perl
(@pxref{Texinfo::Convert::Converter,,,texi2any_internals,Texinfo modules
documentation}).  @xref{Generic Translator @command{texi2any}}.

@cindex Texinfo parsers, discouraging more
If you still cannot resist the temptation of writing a new program
that reads Texinfo source directly, let us give some more caveats:
please do not underestimate the amount of work required.  Texinfo is
by no means a simple language to parse correctly, and remains under
development, so you would be committing to an ongoing task.

@cindex Texinfo language tests
@cindex Tests, of Texinfo language
Extensive tests of the language and processor are
developed with @command{texi2any}; we encourage anyone thinking
of writing a program to process Texinfo to use these test cases
and verify that they give correct results with your new program.

@cindex Man page output, not supported
From time to time, proposals are made to generate traditional Unix man
pages from Texinfo source.  However, because man pages have a strict
conventional format, creating a good man page requires a completely
different source from that needed for the typical Texinfo applications 
of writing a good user tutorial and/or a good reference manual.  This 
makes generating man pages incompatible with the Texinfo design
goal of not having to document the same information in different
ways for different output formats.  You might as well write the man
page directly.

@pindex help2man
@cindex O'Dea, Brendan
As an alternative way to support man pages, you may find the program
@command{help2man} to be useful.  It generates a traditional man page
from the @samp{--help} output of a program.  In fact, the man pages
for the programs in the Texinfo distribution are generated with this.
It is GNU software written by Brendan O'Dea, available from
@uref{https://www.gnu.org/software/help2man}.


@node Writing a Texinfo File
@anchor{Beginning and Ending a File}@c old name
@nodedescription Format of a Texinfo source file.
@chapter Writing a Texinfo File

This chapter describes Texinfo syntax and what is required in a Texinfo 
file, and gives a short sample file.


@node Conventions
@nodedescription General rules for writing a Texinfo file.
@section General Syntactic Conventions
@cindex General syntactic conventions
@cindex Syntactic conventions
@cindex Conventions, syntactic
@cindex Characters, basic input
@anchor{Formatting Commands} @c old name

This section describes the general conventions used in all Texinfo documents.

@itemize @bullet
@item
@cindex Source files, characters used
All printable ASCII characters except @samp{@@}, @samp{@{} and
@samp{@}} can appear in a Texinfo file and stand for themselves.
@samp{@@} is the escape character which introduces commands, while
@samp{@{} and @samp{@}} are used to surround arguments to certain
commands.  To put one of these special characters into the document, put
an @samp{@@} character in front of it, like this: @samp{@@@@},
@samp{@@@{}, and @samp{@@@}}.

@item
@cindex @sortas{at} @@-commands
@cindex Formatting commands
In a Texinfo file, the commands you write to describe the contents of
the manual are preceded by an @samp{@@} character; they are called
@dfn{@@-commands}.  (The @samp{@@} in Texinfo has the same meaning that
@samp{\} has in plain @TeX{}.)

@cindex Braces, when to use
Depending on what they do or what arguments they take, you
need to write @@-commands on lines of their own, or as part of
sentences.  As a general rule, a command requires braces if it mingles 
among other text; but it does not need braces if it is on a line of its 
own.  For more details of Texinfo command syntax, see @ref{Command 
Syntax}.


@item
Whitespace following an @@-command name is optional and (usually)
ignored if present.  The exceptions are contexts when whitespace is
significant, e.g., an @code{@@example} environment.


@item
Texinfo supports the usual quotation marks used in English and in
other languages; see @ref{Inserting Quotation Marks}.

@item
@cindex Multiple dashes in source
@cindex Dashes in source
@cindex Hyphens in source, two or three in a row
@cindex Em dash, producing
@cindex En dash, producing
Use three hyphens in a row, @samp{---}, to produce a long dash---like
this (called an @dfn{em dash}), used for punctuation in sentences.
Use two hyphens, @samp{--}, to produce a medium dash (called an
@dfn{en dash}), used primarily for numeric ranges, as in ``June
25--26''.  Use a single hyphen, @samp{-}, to produce a standard hyphen
used in compound words.  For display on the screen, Info reduces three
hyphens to two and two hyphens to one (not transitively!).  Of course,
any number of hyphens in the source remain as they are in literal
contexts, such as @code{@@code} and @code{@@example}.

@item
@emph{Whitespace}.  Texinfo files are plain text files composed of lines
terminated by the usual newline character (line feed).  Texinfo processors
read input one line at a time.  Paragraphs are terminated by an empty
line or a line containing only spaces. A sequence of several spaces in
text is usually treated the same as a single space (except in
verbatim modes).

@cindex Form feed character
@cindex @kbd{CTRL-l}

Form feed (@kbd{CTRL-l}) characters terminate any open paragraph.
Other form feeds, as well other ASCII whitespace (tab, carriage return)
are treated the same as space characters (although the results may
differ depending on the output format).  Hence, there is not much point
in using these whitespace characters in documents.  Non-ASCII spaces,
such as Unicode ``em space'', are not recognized as whitespace at all,
and will be treated as regular, non-whitespace characters.

However, in verbatim modes, for example in code samples, tab characters
may produce the correct formatting in the output.

@ignore @c too detailed for the manual, but kept for implementation tips
@item
Form feed characters outside of a paragraph are handled as follows:

@table @asis
@item PDF/DVI
Ignored between paragraphs.

@item LaTeX
Ignored in contexts where spaces are ignored except after specific
commands closing braces (@code{@@caption} for example).  Left as is
in the output otherwise.
@c Written as @code{\par@{@}}, a @LaTeX{} macro that starts a paragraph.

@item Info
Ignored in contexts where spaces are ignored except after specific
commands closing braces (@code{@@caption} for example).  In other
contexts, they may be treated as regular spaces (and thus consolidated
with surrounding whitespace).

@item HTML
Written as a numeric entity except contexts where spaces are ignored;
for example, in @samp{@@footnote@{ ^L foo@}}, the form feed is
ignored.

@item XML
Removed format.
Keep them everywhere; in attributes, escaped as @samp{\f}; also,
@samp{\} is escaped as @samp{\\} and newline as @samp{\n}.

@item DocBook
Completely removed, as they are not allowed.
@end table

As you can see, because of these differing requirements of the output
formats, it's not possible to use form feeds completely portably.
@end ignore

@end itemize


@node Comments
@nodedescription Writing comments and ignored text in general.
@section Comments

@cindex Comments
@findex comment
@findex c

You can write comments in a Texinfo file by using the @code{@@comment}
command, which may be abbreviated to @code{@@c}.  Such comments are
for a person looking at the Texinfo source file.  All the text on a
line that follows either @code{@@comment} or @code{@@c} is a comment;
the rest of the line does not appear in the visible output.  (To be
precise, the character after the @code{@@c} or @code{@@comment} must
be something other than a dash or alphanumeric, or it will be taken as
part of the command.)

Often, you can write the @code{@@comment} or @code{@@c} in the middle
of a line, and only the text that follows after the @code{@@comment}
or @code{@@c} command does not appear; but some commands, such as
@code{@@settitle}, work on a whole line.  You cannot use @code{@@comment}
or @code{@@c} within a line beginning with such a command.

@findex DEL @r{(comment character)}
@cindex Catcode for comments in @TeX{}
In cases of nested command invocations, complicated macro definitions,
etc., @code{@@c} and @code{@@comment} may provoke an error when
processing with @TeX{}.  Therefore, you can also use the @kbd{DEL}
character (ASCII 127 decimal, 0x7f hex, 0177 octal) as a true @TeX{}
comment character (catcode 14, in @TeX{} internals).  Everything on
the line after the @kbd{DEL} will be ignored and the next line will
be merged.

@cindex Ignored text
@cindex Unprocessed text
@findex ignore
You can also have long stretches of text ignored by the Texinfo
processors with the @code{@@ignore} and @code{@@end ignore} commands.
Write each of these commands on a line of its own, starting each
command at the beginning of the line.  Text between these two commands
does not appear in the processed output.  You can use @code{@@ignore}
and @code{@@end ignore} for writing comments.  (For some caveats
regarding nesting of such commands, @pxref{Conditional Nesting}.)


@node Minimum
@nodedescription What a Texinfo file must have.
@section What a Texinfo File Must Have
@cindex Minimal Texinfo file (requirements)
@cindex Required in Texinfo file
@cindex Texinfo file minimum

By convention, the name of a Texinfo file ends with one of the 
extensions @file{.texi}, @file{.texinfo}, @file{.txi}, or 
@file{.tex}.  Using @file{.tex} is discouraged as this extension
is already used by @TeX{} and @LaTeX{} input files.  The most common
and recommended extension is @file{.texi}.  The name of a Texinfo
file should only contain ASCII characters.

The output name is based on the input file name, in the default case.
First, any of the extensions @file{.texi}, @file{.tex}, @file{.txi},
or @file{.texinfo} is removed from the input file name; then,
the output format specific extension is added---@file{.html} when
generating HTML, @file{.info} when generating Info, etc.
The output name should only contain ASCII
characters@footnote{@command{texi2any} can handle non ASCII characters
in input file names, but non ASCII characters in output name will create
problems for some output formats, especially for cross-references.}.

@cindex Requirements for formatting
@cindex Minimal requirements for formatting
@cindex Formatting requirements
In order to be made into a printed manual, a Texinfo file must begin
with a line like this:

@example
@group
\input texinfo
@end group
@end example

@noindent
The contents of the file follow this beginning, and then you
must end the Texinfo source with a line like this:

@example
@@bye
@end example

@findex \input @r{(raw @TeX{} startup)}

The @code{@@bye} line at the end of the file on a line of its own tells
@TeX{} that the file is ended and to stop formatting.  If you
leave this out, you'll be dumped at @TeX{}'s prompt at the end of the
run.

Furthermore, you will usually provide a Texinfo file with a title,
a title page, indices, and the like, all of which are explained in
this manual.  But the minimum, which can be useful for short
documents, is just the one line at the beginning and the one line
at the end.

Without additional information, the input and output encodings are
assumed to be UTF-8, an universal codeset compatible with 7-bit
ASCII.


@node Short Sample Texinfo File
@nodedescription A short sample Texinfo file.
@anchor{Short Sample}@c
@anchor{Sample Beginning}@c
@section Short Sample
@cindex Sample Texinfo file, no comments

Here is a short sample Texinfo file.

@example
\input texinfo
@@settitle Sample Manual 1.0

@@copying
This is a short example of a complete Texinfo file.

Copyright @@copyright@{@} 2026 Free Software Foundation, Inc.
@@end copying
@@documentinfo
@@title Sample Title
@@end documentinfo
@@maketitle

@@contents

@@node Top
@@top GNU Sample

This manual is for GNU Sample
(version @@value@{VERSION@}, @@value@{UPDATED@}).

@@node First Chapter
@@nodedescription The first chapter is the only chapter in this sample.
@@chapter First Chapter

@@cindex chapter, first
This is the first chapter.
@@cindex index entry, another

@group
Here is a numbered list.

@@enumerate
@@item
This is the first item.

@@item
This is the second item.
@@end enumerate
@end group


@@node First Section
@@section First Section

First section of first chapter.


@@node Second Section
@@section Second Section

Second section of first chapter.


@@node Index
@@nodedescription Complete Index
@@unnumbered Index

@@printindex cp

@@bye
@end example


@node Texinfo File Header
@nodedescription The first lines.
@section Texinfo File Header
@cindex Header for Texinfo files
@cindex Texinfo file header

Texinfo files start with the line:

@example
\input texinfo
@end example

The @samp{\input texinfo} line tells @TeX{} to use the
@file{texinfo.tex} file, which tells @TeX{} how to translate the Texinfo
@@-commands into @TeX{} typesetting commands.  (Note the use of the
backslash, @samp{\}; this is correct for @TeX{}.)

It makes sense to include any command that affects document formatting
as a whole in the header.  The @code{@@settitle} line is usually
present at the beginning of the header:

@example
@@settitle Sample Manual 1.0
@end example

The @code{@@settitle} line specifies a title for the page headers
(or footers) of the printed manual, and the default title and document
description for the @samp{<head>} in HTML@.  @code{@@synindex}
(@pxref{@code{@@synindex}}), for instance, is another command often
included in the header.

The start of the Texinfo file up to the first content that is output
as part of the main body of the document is the @dfn{preamble}.
It includes the header, @ref{Document Permissions} and @ref{Titlepage & Copyright Page}
specification.  It is important for the @LaTeX{} output format as the
end of preamble is where the @code{\begin@{document@}} line is output.  In
other output formats it may be used to determine how some special output is
formatted, for example @ref{@code{@@copying}} output as a comment
at the beginning of output files, or the language used in file headers.



@node First Line
@subsection The First Line of a Texinfo File
@nodedescription The first line of a Texinfo file.
@cindex First line of a Texinfo file
@cindex Beginning line of a Texinfo file
@cindex Header of a Texinfo file

Every Texinfo file that is to be the top-level input to @TeX{} must begin
with a line that looks like this:

@example
\input texinfo
@end example

When the file is processed by @TeX{}, the @samp{\input texinfo} command
tells @TeX{} to load the macros needed for processing a Texinfo file.
These are in a file called @file{texinfo.tex}, which should have been
installed on your system along with either the @TeX{} or Texinfo
software.  @TeX{} uses the backslash, @samp{\}, to mark the beginning of
a command, exactly as Texinfo uses @samp{@@}.  The @file{texinfo.tex}
file causes the switch from @samp{\} to @samp{@@}; before the switch
occurs, @TeX{} requires @samp{\}, which is why it appears at the
beginning of the file.

You may optionally follow this line with a comment to tell GNU Emacs
to use Texinfo mode when the file is edited:

@example
\input texinfo   @@c -*-texinfo-*-
@end example

@noindent This may be useful when Emacs doesn't detect the file type 
from the file extension automatically.


@node @code{@@setfilename}
@nodedescription Give the name of the output file.
@subsection @code{@@setfilename}: Set the Output File Name

@anchor{setfilename}@c old name
@c used in references when the reference is not about @setfilename
@c in particular, but about the output file name, be it from @setfilename
@c or from the input file name.
@anchor{Setting the Output File Name}
@findex setfilename
@cindex output file name

The @code{@@setfilename} line specifies the name of the output file to
be generated by @command{texi2any}.  This command is ignored for
@TeX{} formatting.  When present, it should be the first Texinfo
command (that is, after @samp{\input texinfo}).  Write the
@code{@@setfilename} command at the beginning of a line and follow it
on the same line by the Info file name.

@example
@@setfilename @var{info-file-name}
@end example

The name must be different from the name of the Texinfo file.
There are two conventions for choosing the name: you
can either remove the extension (such as @samp{.texi}) entirely from
the input file name, or (recommended) replace it with the @samp{.info}
extension.  It is not advised to base the @code{@@setfilename} name
on a entirely different name than the input file name.

@cindex Ignored before @code{@@setfilename}
@cindex @samp{\input} source line ignored
When a @code{@@setfilename} line is present, the Texinfo processors
ignore everything written before the @code{@@setfilename} line.  This
is why the very first line of the file (the @code{\input} line) does
not show up in the output.

If there is no @code{@@setfilename} line, @command{texi2any} uses the
input file name to determine the output name (@pxref{Minimum}).  The
@code{\input} line is still ignored in this processing, as well
as leading blank lines.

When producing another output format, @command{texi2any} will replace any
final extension with the output format-specific extension (@samp{html}
when generating HTML, for example), or add a dot followed by the
extension (@samp{.html} for HTML) if the given name has no extension.

@@-commands are not allowed in @code{@@setfilename}, except for
@code{@@@@}, @code{@@@{}, @code{@@@}} and associated @@-commands
such as @code{@@atchar@{@}}.

@code{@@setfilename} used to be required by the Texinfo processors
and some other programs.  This should not be the case any more;
@code{@@setfilename} can be omitted.  If the Texinfo input is
processed from standard input, without an input file name to deduce the
base file name from, @code{@@setfilename} could still be relevant.
This is not the only way, however: @option{--output} option specifies
the output file name on the @command{texi2any} command-line
(@pxref{Invoking @command{texi2any}}).

@cindex Length of file names
@cindex File name collision
@cindex Info file name, choosing
Although an explicit @samp{.info} extension is preferable, some
operating systems cannot handle long file names.  You can run into a
problem even when the file name you specify is itself short enough.
This occurs because the Info formatters split a long Info file into
short indirect subfiles, and name them by appending @samp{-1},
@samp{-2}, @dots{}, @samp{-10}, @samp{-11}, and so on, to the original
file name.  (@xref{Tag and Split Files}.)  The subfile name
@file{texinfo.info-10}, for example, is too long for old systems with
a 14-character limit on filenames; so the Info file name for this
document could be @file{texinfo} rather than @file{texinfo.info} on
such a system.  @code{@@setfilename} is a way to specify an
alternative name.


@node @code{@@settitle}
@nodedescription Create a title for the printed work.
@subsection @code{@@settitle}: Set the Document Title

@anchor{settitle}@c old name
@findex settitle
@cindex Document title, specifying

A Texinfo file should contain a line that looks like this:

@example
@@settitle @var{title}
@end example

Write the @code{@@settitle} command at the beginning of a line and
follow it on the same line by the title.  Do not write anything else
on the line.  The @code{@@settitle} command should precede everything
that generates actual output.  The best place for it is right after
the @code{@@setfilename} command, if present (described in the previous
section).

This command gives the title to use in a header or footer
for double-sided printed output, in case such headings are output.  For
more on headings for printed output, see @ref{Heading Generation}.

@cindex @code{<title>} HTML tag
In HTML, @var{title} serves as the document @samp{<title>} and it becomes
the default document description in the @samp{<head>} part.

When the title page is used in the output, as is generally the case for printed
output, the title in the @code{@@settitle} command does not affect the title as
it appears on the title page.  Thus, the two do not need not to match exactly.
A practice we recommend is to include the version or edition number of the
manual in the @code{@@settitle} title; on the title page, the version number
generally appears as a @code{@@subtitle} so it would be omitted from the
@code{@@title}.  @xref{Titlepage & Copyright Page}.


@node Preamble
@nodedescription Start of the Texinfo file up to first content.
@subsection Preamble
@cindex Preamble
@cindex Texinfo Preamble

The @dfn{preamble} starts at the beginning of the Texinfo file and continues
until the first directly output material.  It typically includes the
file header (@pxref{Texinfo File Header}), the @code{@@copying} block
specifying the document permissions (@pxref{@code{@@copying}}) and the
title page specifications (@pxref{Titlepage & Copyright Page}).

The preamble may contain commands that affect document formatting
as a whole but which do not produce output, or do not produce output
straight away, such as @code{@@settitle} (@pxref{@code{@@settitle}}),
@code{@@documentlanguage}, (@pxref{@code{@@documentlanguage}}),
commands setting the headings, controlling indentation or hyphenation,
or the table of contents (@pxref{Contents}).

@ignore
The preamble can also contain
raw formatter commands (@pxref{Raw Formatter Commands}), but it is not checked
that the content of these commands is actually preamble material and not
regular output.
@end ignore

Any text that starts a paragraph, @@-commands that are formatted
as quotations, tables, lists and so on, and @code{@@node} (@pxref{Nodes})
and chapter structuring commands (@pxref{Chapter Structuring}) end the
preamble.

The concept of the preamble is significant for @LaTeX{} output, as the
@code{\begin@{document@}} line is output at the end of the preamble.

In plaintext, the preamble is simply output as usual at the beginning of the
document; for example, a @code{@@contents} in the preamble is output as
the table of contents (@pxref{Contents}).  

There is not much special treatment of the preamble for HTML and Info
output either.  However, some settings current at the very end of
the preamble may be used for the document as a whole, regardless of
what follows.  This may apply to commands specifying the indentation,
or the language (@pxref{@code{@@documentlanguage}}).

For example, for the following document, the HTML and Info copying
comments are formatted with @code{@@documentlanguage} set to @samp{pt},
as it is the last @code{@@documentlanguage} before the end of the
preamble.

@example
@group
\input texinfo
@@documentlanguage fr

@@copying
The copying information @@error@{@} some text
@@end copying

@@documentlanguage pt

Text ending the preamble

@@documentlanguage de

@@node Top

@end group
@end example


@node Start and End of Header
@nodedescription Formatting a region in Emacs requires this.
@subsection Start and End of Header for Emacs
@anchor{Start of Header}@c old name
@cindex Start of header line

In Emacs, start- and end-of-header lines can be used to enclose commands that
globally affect the document in the Texinfo preamble.  This allows you to
format only part of a Texinfo file for Info or printing.
@xref{@code{texinfo-format} commands}.

A start-of-header line is a Texinfo comment that looks like this:

@example
@@c %**start of header
@end example

Write the start-of-header line on the second line of a Texinfo file.
Follow the start-of-header commands that globally affect the document
formatting, such as @code{@@settitle}, @code{@@synindex} or
@code{@@footnotestyle}; and then by an @w{end-of-header} line.

@anchor{End of Header}@c old name
@cindex End of header line

A end-of-header line is a Texinfo comment that looks like this:

@example
@@c %**end of header
@end example

The odd string of characters, @samp{%**}, is to ensure that no other
comment is accidentally taken for a start-of-header line.  You can
change it if you wish by setting the @code{tex-start-of-header} and/or
@code{tex-end-of-header} Emacs variables.  @xref{Texinfo Mode Printing}.

The start- and end-of-header lines are not part of the Texinfo format
specification, which is why they are implemented with comments.


@node Directory Category
@nodedescription A category for a manual.
@section Directory Category

@findex dircategory
Use the @code{@@dircategory} command to specify a category
for the manual.

@code{@@dircategory} commands are usually followed by
@code{@@direntry} blocks, which are used by @command{install-info}.
@xref{Installing Dir Entries}, for an example of how these commands
are used.

The first @code{@@dircategory} command in a manual is the category for
the entire manual.  Subsequent uses of @code{@@dircategory} set the category
for following @code{@@direntry} blocks only.

@cindex Dir categories, choosing
@cindex Categories, choosing
There is no consistency in the use of directory categories across
manuals, and there is unlikely ever to be, as authors work on Texinfo
documentation independently with no central co-ordination that would
result in such consistency.

It is possible for users or operating system distributions to edit
categories in Info or Texinfo files, if a logical organization
within @code{dir} files is something that they value.

Authors of manuals may consider using some of the following categories
for manuals.  For a package that installs many manuals (such as Emacs),
it may be a good idea to use package-specific category, or categories,
to group its manuals.

@c from util/dir-example and https://www.gnu.org/manual/manual.html
@c
@c we used to recommend looking at Free Software Directory categories
@c but these have changed

@display
Archiving
Audio
Business and productivity
Compression
Database
Dictionaries
Documentation translation
Editors
Education
Email
Fonts
Games
Graphics
Health
Interface
Internet applications
Live communications
Localization
Mathematics
Music
Network applications
Printing
Security
Science
Software development
Software libraries
Spreadsheets
System administration
Telephony
Text creation and manipulation
Version control
Video
Web authoring
@end display


@node Document Permissions
@nodedescription Ensuring your manual is free.
@anchor{Software Copying Permissions}@c old node name
@section Document Permissions
@cindex Document permissions
@cindex Copying permissions

This segment describes the document and contains the copyright notice 
and copying permissions.  This is done with the @code{@@copying} command.
A real manual includes more text here, according to the license under
which it is distributed.

@example
@group
@@copying
This is a short example of a complete Texinfo file, version 1.0.

Copyright @@copyright@{@} 2026 Free Software Foundation, Inc.
@@end copying
@end group
@end example

The copyright notice and copying permissions for a document need to
appear in several places in the various Texinfo output formats.
Therefore, Texinfo provides a command (@code{@@copying}) to declare
this text once, and another command (@code{@@insertcopying}) to
insert the text at appropriate points.

For plain text output, you must insert the copyright information
explicitly if you want it to appear, as it is not otherwise output.
For instance, you could have the following near the start of the Texinfo
file:

@example
@@ifplaintext
@@insertcopying
@@end ifplaintext
@end example

You could include other title-like information for the plain text
output in the same place.

If the document is a software manual, the software is typically under a
different license---for GNU and many other free software packages,
software is usually released under the GNU GPL, and manuals are
released under the GNU FDL@.  It is helpful to state the license of
the software of the manual, but giving the complete text of the
software license is not necessarily required.


@node @code{@@copying}
@nodedescription Declare the document's copying permissions.
@subsection @code{@@copying}: Declare Copying Permissions

@anchor{copying}@c old name
@findex copying

The @code{@@copying} command should be given very early in the document;
the recommended location is right after the header material
(@pxref{Texinfo File Header}).  It conventionally consists of a sentence
or two about what the program is, identification of the documentation
itself, the legal copyright line, and the copying permissions.  Here is
a skeletal example:

@example
@@copying
This manual is for @var{program} (version @var{version}, updated
@var{date}), which @dots{}

Copyright @@copyright@{@} @var{years} @var{copyright-owner}.

@@quotation
Permission is granted to @dots{}
@@end quotation
@@end copying
@end example

The @code{@@quotation} has no legal significance; it's there to improve
readability in some contexts.

The text of @code{@@copying} appears as a comment at the beginning of Info
and HTML output files.  This information is also output at the beginning
of the DocBook output files using appropriate markup.  It is @emph{not}
output implicitly in plain text or printed output; it's up to you to use
@code{@@insertcopying} to emit the copying information.  See the next section
for details.

The @code{@@copyright@{@}} command generates a @samp{c} inside a
circle when the output format supports this glyph (print and HTML
always do, for instance).  When the glyph is not supported in the
output, it generates the three-character sequence @samp{(C)}.

The copyright notice itself has the following legally-prescribed
form:

@example
Copyright @copyright{} @var{years} @var{copyright-owner}.
@end example

@cindex Copyright word, always in English
The word `Copyright' must always be written in English, even if the
document is otherwise written in another language.  This is due to
international law.

@cindex Years, in copyright line
The list of years should include all years in which a version was
completed (even if it was released in a subsequent year).  It is
simplest for each year to be written out individually and in full,
separated by commas.

@cindex Copyright holder for FSF works
@cindex Holder of copyright for FSF works
@cindex Owner of copyright for FSF works
The copyright owner (or owners) is whoever holds legal copyright on the
work.  In the case of works assigned to the FSF, the owner is `Free
Software Foundation, Inc.'.

The copyright `line' may actually be split across multiple lines, both
in the source document and in the output.  This often happens for
documents with a long history, having many different years of
publication.  If you do use several lines, do not indent any of them
(or anything else in the @code{@@copying} block) in the source file.

@xref{Copyright Notices,,, maintain, GNU Maintainer Information}, for
additional information.  @xref{GNU Sample Texts}, for the full text to
be used in GNU manuals.  @xref{GNU Free Documentation License}, for
the license itself under which GNU and other free manuals are
distributed.


@node @code{@@insertcopying}
@nodedescription Where to insert the permissions.
@subsection @code{@@insertcopying}: Include Permissions Text

@anchor{insertcopying}@c old name
@findex insertcopying
@cindex Copying text, including
@cindex Permissions text, including
@cindex Including permissions text

The @code{@@insertcopying} command is simply written on a line by
itself, like this:

@example
@@insertcopying
@end example

This inserts the text previously defined by @code{@@copying}.  To meet
legal requirements, it must be used on the copyright page in the printed
manual (@pxref{Copyright}).

The @code{@@copying} command itself causes the permissions text to
appear in an Info file @emph{before} the first node.  The text is also
copied into the beginning of each split Info output file, as is legally
necessary.  This location implies a human reading the manual using Info
does @emph{not} see this text (except when using the advanced Info
command @kbd{g *}). This does not matter for legal purposes,
because the text is present.  But to get a visible text in the output,
@code{@@insertcopying} should be used.

Similarly, the @code{@@copying} text is automatically included at the
beginning of each HTML output file, as an HTML comment.  Again, this
text is not visible without @code{@@insertcopying} (unless the reader views the
HTML source).

The permissions text defined by @code{@@copying} also appears
automatically at the beginning of the DocBook output files
using appropriate markup.  @code{@@insertcopying} can be used
to output the permission text within normal text.


@node Titlepage & Copyright Page
@nodedescription Creating the title and copyright pages.
@section Title and Copyright Pages

@cindex Copyright page
@cindex Printed permissions
@cindex Permissions, printed
The first page of a printed book is usually the @dfn{title page},
which contains the name of the book and the author.  Copyright and
publication information is usually printed on the next page; we refer
to this page as the @dfn{copyright page}.  As this is on the back (verso)
of the title page, this page is also known as the @dfn{title verso}.
@ignore
(By international treaty, the copyright notice for a book must be either
on the title page or on the back of the title page.)
@end ignore

@cindex Document metadata
Texinfo provides commands for you to provide the document title, any
subtitle, the name of the author (or names of several authors), and copying
and publication information for the document.  This @dfn{metadata}
is used for the contents of the title page and copyright page.
Likewise, this information appears in the output in some form for other
output formats, even if not displayed as a title page.

Texinfo provides at least three different ways to provide this metadata
and to generate the title and copyright pages, which are described in
the following subsections.

In HTML, no titlepage is output, in the default case.  The best way to get a
title page similar to printed manuals is to set the @code{NO_TOP_NODE_OUTPUT}
customization variable (@pxref{@code{NO_TOP_NODE_OUTPUT}}).

@findex shorttitlepage
@cindex Bastard title page
@cindex Title page @subentry bastard
For sufficiently simple documents, and for the bastard title page in
traditional book front matter, Texinfo also provides a command
@code{@@shorttitlepage} which takes the rest of the line as the title.
The argument is typeset on a page by itself and followed by a blank
page.  In HTML, @code{@@shorttitlepage} can play the same role as
@code{@@settitle}, if @code{@@settitle} is not set.  @xref{@code{@@settitle}}.


@node Document Metadata
@nodedescriptionblock
The @code{@@documentinfo}, @code{@@copying}, @code{@@publication}, and
@code{@@maketitle} commands.
@end nodedescriptionblock
@subsection Document Metadata and the @code{@@maketitle} Command

@findex documentinfo
The simplest way to define document metadata used for the title page is
using the @code{@@documentinfo} command.  Here is a template:

@example
@group
@@documentinfo
@@title @var{name-of-manual-when-printed}
@@subtitle @var{subtitle-if-any}
@@subtitle @var{second-subtitle}
@@author @var{author}
@@end documentinfo
@end group
@end example

You should only use the @code{@@title} command once within the
@code{@@documentinfo} block.  You can use the @code{@@subtitle} command more
than once, and the order that any @code{@@subtitle} commands appear in the
block is kept when the Texinfo file is processed.  Likewise, you can
use @code{@@author} more than once.  (However, the order of @code{@@title},
@code{@@subtitle}, and @code{@@author} commands relative to each other is
not significant.)

Other Texinfo code found in @code{@@documentinfo} is output in metadata
sections of output formats.  Texinfo processors do not interpret this
additional code especially, therefore you often need to use
raw formatter commands such that output format metadata specific
formatting is produced (@pxref{Raw Formatter Commands}).  An example
with HTML, EPUB and Docbook metadata:
@c similar to a t/*.t test code, but simplified to be shorter

@example
@@documentinfo
@@title The Title
@@ifepub
@@html
<dc:creator id="creator">Some Body</dc:creator>
<meta refines="#creator" property="role" scheme="marc:relators"
    id="role">aut</meta>
@@end html
@@end ifepub
@@ifnotepub
@@html
<meta name="creator" content="Some Body" />
@@end html
@@end ifnotepub
@@docbook
<author>
  <firstname>Some</firstname><surname>Body</surname>
  <affiliation><jobtitle>Director</jobtitle>
    <orgname>The School of Somewhere</orgname>
  </affiliation>
</author>
@@end docbook
@@end documentinfo
@end example

The information for the copyright page appears within the @code{@@copying}
and @code{@@publication} commands.  @xref{Document Permissions} for more
discussion of @code{@@copying}.

@findex publication
The @code{@@publication} command works very similarly to @code{@@copying}.
The Texinfo processors save the contents of this block when they encounter
it in the Texinfo source.  You use this command to provide information
about the publication of the document, such as the address of the
publisher, or ISBN@.  You use this block for information that would go an
``imprint'' or ``colophon'' in a printed book.

@findex maketitle
Finally, to actually output the title and copyright pages, you use the
@code{@@maketitle} command.  Write this command on a line by itself.
This draws together the available information to produce these two pages.

These commands would be used like this:

@example
@@copying
@var{copying-info}
@@end copying
@@publication
Published by @var{publisher-name}
@var{publisher-address}
@@end publication
@@maketitle
@end example


@node @code{@@titlepage}
@nodedescription Create a title for the printed document.
@subsection @code{@@titlepage}

@anchor{titlepage}@c old name
@cindex Title page
@findex titlepage

An alternative to using @code{@@maketitle} to create title and copyright
pages is to use the @code{@@titlepage} command.  Any material enclosed between
@code{@@titlepage} and @code{@@end titlepage} lines is directly output
for a printed manual.  Here is a basic example:

@example
@group
@@titlepage
@@title Sample Title
@end group
@@c The following two commands start the copyright page.
@@page
@@vskip 0pt plus 1filll
@@insertcopying

Published by @dots{}

Cover art by @dots{}
@@end titlepage
@end example

Start the material for the title page and following copyright page
with @code{@@titlepage} on a line by itself and end it with
@code{@@end titlepage} on a line by itself.

The material before the @samp{@@page} line is used for the title page.
The following subsubsections explain the two ways that the @code{@@titlepage}
command might be used within a Texinfo document to produce a title page,
the first closer to the previous method with @code{@@documentinfo},
the second with more explicit formatting.

However, the copyright page is always produced in the same way with
@code{@@titlepage}.


@anchor{Copyright}
@subsubheading Copyright Page
@findex page@r{, within @code{@@titlepage}}
By using the @code{@@page} command, you can force a page break within the
region delineated by the @code{@@titlepage} and @code{@@end titlepage}
commands and thereby create more than one unnumbered page.  This is how
the copyright page is produced.  (The @code{@@titlepage} command might
perhaps have been better named the @code{@@titleandadditionalpages}
command, but that would have been rather long!)

@findex vskip @r{@TeX{} vertical skip}
@cindex filll @r{@TeX{} dimension}
To push the copyright notice and the other text on the copyright page
towards the bottom of the page, use the following incantation after
@code{@@page}:

@example
@@vskip 0pt plus 1filll
@end example

@noindent
The @code{@@vskip} command inserts whitespace in the @TeX{} output; it
is ignored in all other output formats.  The @samp{0pt plus 1filll}
means to put in zero points of mandatory whitespace, and as much
optional whitespace as needed to push the following text to the bottom
of the page.  Note the use of three @samp{l}s in the word
@samp{filll}; this is correct.

To insert the copyright text itself, write @code{@@insertcopying}
next (@pxref{Document Permissions}):

@example
@@insertcopying
@end example

@noindent (This is required for outputting the copying text when
using @code{@@titlepage}, unlike with @code{@@maketitle} where this
text is output automatically.)

Follow the copying text by the publisher, ISBN numbers, cover art
credits, and other such information.



@node @code{@@title @@subtitle @@author}
@nodedescriptionblock
The @code{@@title}, @code{@@subtitle}, and @code{@@author} commands.
@end nodedescriptionblock
@subsubsection @code{@@title}, @code{@@subtitle}, and @code{@@author}

@anchor{title subtitle author}@c old name
@findex title
@findex subtitle
@findex author

One way to use @code{@@titlepage} is to use @code{@@title}, @code{@@subtitle},
and @code{@@author} commands inside the @code{@@titlepage} block.  With this
method, you do not specify any of the actual formatting of the title page.
You specify the text you want, and Texinfo does the formatting.
The usual formatting consist of black rules under
the title and author lines and the subtitle text set flush to the
right-hand side of the page.

You can use the @code{@@title}, @code{@@subtitle}, and @code{@@author}
commands to create a title page in which the vertical and horizontal
spacing is done for you automatically.

Write the @code{@@title}, @code{@@subtitle}, or @code{@@author}
commands at the beginning of a line followed by the title, subtitle,
or author.  The @code{@@author} command may be used for a quotation in
an @code{@@quotation} block (@pxref{@code{@@quotation}});
except for that, it is an error to use any of these commands outside
of @code{@@titlepage}.

The @code{@@title} command normally produces a line in which the title is set
flush to the left-hand side of the page in a larger than normal font.
The title is underlined with a black rule.  The title must be given on
a single line in the source file; it will be broken into multiple
lines of output is needed.

For long titles, the @code{@@*} command may be used to specify the
line breaks in long titles if the automatic breaks do not suit.  Such
explicit line breaks are generally reflected in all output formats; if
you only want to specify them for the printed output, use a
conditional (@pxref{Conditionals}).  For example:

@example
@@title This Long Title@@inlinefmt@{tex,@@*@} Is Broken in @@TeX@{@}
@end example

The @code{@@subtitle} command normally sets subtitles in a normal-sized font
flush to the right-hand side of the page.

The @code{@@author} command normally sets the names of the author
or authors in a middle-sized font flush to the left-hand side of the
page on a line near the bottom of the title page.  The names are
followed by a black rule that is thinner than the rule that normally
underlines the title.

There are two ways to use the @code{@@author} command: you can write
the name or names on the remaining part of the line that starts with
an @code{@@author} command:

@example
@@author by Jane Smith and John Doe
@end example

@noindent
or you can write the names one above each other by using multiple
@code{@@author} commands:

@example
@group
@@author Jane Smith
@@author John Doe
@end group
@end example

@need 950
A template for this method looks like this:

@example
@group
@@titlepage
@@title @var{name-of-manual-when-printed}
@@subtitle @var{subtitle-if-any}
@@subtitle @var{second-subtitle}
@@author @var{author}
@@page
@dots{}
@@end titlepage
@end group
@end example


@node @code{@@titlefont @@center @@sp}
@nodedescriptionblock
The @code{@@titlefont}, @code{@@center}, and @code{@@sp} commands.
@end nodedescriptionblock
@subsubsection @code{@@titlefont}, @code{@@center}, and @code{@@sp}

@anchor{titlefont center sp}@c old name
@findex titlefont
@findex center
@findex sp @r{(titlepage line spacing)}

Texinfo also provides a second method for creating a title page,
using typesetting commands that are not to be used in the main text.
This method uses the @code{@@titlefont}, @code{@@sp}, and @code{@@center} 
commands to generate a title page in which the words on the page are
centered.

Use the @code{@@titlefont} command to select a large font suitable for
the title itself.  You can use @code{@@titlefont} more than once if you
have an especially long title.

For HTML output, each @code{@@titlefont} command produces an
@code{<h1>} heading, but the HTML document @code{<title>} is not
affected.  For that, you could put a @code{@@settitle} command before
the @code{@@titlefont} command (@pxref{@code{@@settitle}}).

@need 700
For example:

@example
@@titlefont@{Texinfo@}
@end example

Use the @code{@@center} command at the beginning of a line to center
the remaining text on that line.  Thus,

@example
@@center @@titlefont@{Texinfo@}
@end example

@noindent
centers the title, which in this example is ``Texinfo'' printed
in the title font.

Use the @code{@@sp} command to insert vertical space.  For example:

@example
@@sp 2
@end example

@noindent
This inserts two blank lines on the printed page.
(@xref{@code{@@sp}}, for more information about the @code{@@sp}
command.)

A template for this method looks like this:

@example
@group
@@titlepage
@@sp 10
@@center @@titlefont@{@var{name-of-manual-when-printed}@}
@@sp 2
@@center @var{subtitle-if-any}
@@sp 2
@@center @var{author}
@dots{}
@@end titlepage
@end group
@end example

The spacing of the example fits an 8.5 by 11 inch manual.


@node Title Page Version
@nodedescription Version of a program or edition of a manual.
@subsection Displaying the Version or Edition on the Title Page

When you write a manual about a computer program, you should write the
version of the program to which the manual applies on the title page.
You would typically include these in a subtitle.
If the manual changes more frequently than the program or is independent
of it, you should also include an edition number@footnote{We have found
that it is helpful to refer to versions of independent manuals as
`editions' and versions of programs as `versions'; otherwise, we find we
are liable to confuse each other in conversation by referring to both
the documentation and the software with the same words.} for the manual.
This helps readers keep track of which manual is for which version of
the program.  (The `Top' node should also contain this information; see
@ref{The Top Node}.)


@node Heading Generation
@nodedescription Turn on page headings after the title and copyright pages.
@subsection Heading Generation

@anchor{end titlepage}@c old name
@cindex Generating page headings

Texinfo has two standard page heading formats, one for documents
printed on one side of each sheet of paper (single-sided printing),
and the other for documents printed on both sides of each sheet
(double-sided printing).

In full generality, you can control the headings in different ways:

@itemize @bullet
@item
The conventional way is to write a @code{@@setchapternewpage} command
before the title page commands.

Most documents are formatted with the standard single-sided or
double-sided headings, (sometimes) using @code{@@setchapternewpage
odd} for double-sided printing and (almost always) no
@code{@@setchapternewpage} command for single-sided printing
(@pxref{@code{@@setchapternewpage}}).

@item
Alternatively, you can use the @code{@@headings} command to prevent
page headings from being generated or to start them for either single
or double-sided printing. To turn off headings, write @code{@@headings off}.
@xref{@code{@@headings}}.

@item
Or, you may specify your own page heading and footing format.
@xref{Headings}.
@end itemize


@node Contents
@nodedescription How to create a table of contents.
@section Generating a Table of Contents
@cindex Table of contents
@cindex Contents, table of
@cindex Short table of contents
@findex contents
@findex summarycontents
@findex shortcontents

The @code{@@chapter}, @code{@@section}, and other structuring commands
(@pxref{Chapter Structuring}) supply the information to make up a
table of contents, but they do not cause an actual table to appear in
the manual.  To do this, you must use the @code{@@contents} and/or
@code{@@summarycontents} command(s).

@table @code
@item @@contents
Generates a table of contents in a printed manual, including all
chapters, sections, subsections, etc., as well as appendices and
unnumbered chapters.  Headings generated by @code{@@majorheading},
@code{@@chapheading}, and the other @code{@@@dots{}heading} commands
do not appear in the table of contents (@pxref{Structuring Command
Types}).

@item @@shortcontents
@itemx @@summarycontents
(@code{@@summarycontents} is a synonym for @code{@@shortcontents}.)

Generates a short or summary table of contents that lists only the
chapters, appendices, and unnumbered chapters.  Sections, subsections
and subsubsections are omitted.  Only a long manual needs a short
table of contents in addition to the full table of contents.
@end table

Both contents commands should be written on a line by themselves, and
placed near the beginning of the file, after the @code{@@end
titlepage} (@pxref{@code{@@titlepage}}) or the @code{@@end
documentinfo} (@pxref{Document Metadata}), before any sectioning
command.  The contents commands automatically generate a chapter-like
heading at the top of the first table of contents page, so don't
include any sectioning command such as @code{@@unnumbered} before
them.

Since an Info file uses menus instead of tables of contents, the Info
formatting commands ignore the contents commands.  But the contents
are included in plain text output and in other output formats, such
as HTML.

In HTML output, the links in the short table of contents point to
corresponding entries in the full table of contents rather than the text
of the document. The links in the full table of contents point to the
main text of the document.

@code{@@shortcontents} is not implemented for @LaTeX{} output.


@node The Top Node
@nodedescription Creating the `Top' node
@section The `Top' Node
@cindex Top node
@cindex Node, @samp{Top}
@anchor{Top Node Example}@c

The `Top' node is the node in which a reader enters an Info manual.
As such, it should contain a very brief description of the manual
(including the version number).  The contents of the `Top' node do
not appear in printed output nor in DocBook output.

It is conventional to write a line with a @code{@@top} command
containing the title of the document immediately after the
@code{@@node Top} line (@pxref{@code{@@top} Command}).

We repeat the short description from the beginning of
the @samp{@@copying} text, but there's no need to repeat the copyright
information, so we don't use @samp{@@insertcopying} here.

In the Info output (and sometimes HTML output), the `Top' node usually
contains a top-level @dfn{menu} listing the chapters, and possibly a
@dfn{detailed menu} listing all the nodes in the entire document.  It
is not usually necessary to give such a menu in the Texinfo source, as
@command{texi2any} generates these menus automatically.  However, the
following example shows how you would use the @code{@@menu} command to
give a menu in the `Top' node:


@cindex Top node example
@example
@@node Top
@@top Short Sample

This is a short sample Texinfo file.

@group
@@menu
* First Chapter::    The first chapter is the
                       only chapter in this sample.
* Index::            Complete index.
@@end menu
@end group
@end example


@node Master Menu Parts
@subsection Parts of a Master Menu
@cindex Master menu
@cindex Menu, master
@cindex Parts of a master menu

A @dfn{master menu} is the main menu.  It is customary to include a
detailed menu listing all the nodes in the document in this menu.
Like any other menu, a master menu is enclosed in @code{@@menu} and
@code{@@end menu} and does not appear in the printed output nor in
DocBook output.

The master menu contains entries for the major nodes in the Texinfo
file: the nodes for the chapters, chapter-like sections, and the
appendices, followed by nodes for the indices.

@findex detailmenu
@cindex Detailed menu

You may choose to follow these entries with a @dfn{detailed menu}.
This lists other, lower-level nodes, often ordered by chapter.
These items may be a convenience for an inquirer who can go directly
to a particular node when searching for specific information, rather
than going through an intermediate menu.  If you use a detailed menu
in your master menu, mark it with the @code{@@detailmenu @dots{}
@@end detailmenu} environment.

Each section in the menu can be introduced by a descriptive line.  So
long as the line does not begin with an asterisk, it will not be
treated as a menu entry.  (@xref{Writing a Menu}, for more
information.)

For example, the master menu for this manual looks like the following
(but has many more entries):

@example
@group
@@menu
* Copying Conditions::  Your rights.
* Overview::            Texinfo in brief.
@dots{}
@end group
@group
* Variables Index::
* General Index::
@end group

@group
@@detailmenu
--- The Detailed Node Listing ---

Overview of Texinfo

* Reporting Bugs:: @dots{}
@dots{}
@end group

@group
Beginning a Texinfo File

* Sample Beginning:: @dots{}
@dots{}
@@end detailmenu
@@end menu
@end group
@end example


@node The Body of the Document
@nodedescription The rest of the nodes.
@section The Body of the Document

@cindex Frontmatter, text in
The body segment contains all the text of the document.
A manual is divided into one or more @dfn{nodes} (@pxref{Nodes}).  
The example illustrates a chapter made of three nodes, one
for introductory material in the chapter, and two sections.
The introductory material contains an enumerated list.

@example
@group
@@node First Chapter
@@chapter First Chapter

@@cindex chapter, first
This is the first chapter.
@@cindex index entry, another

Here is a numbered list.

@@enumerate
@@item
This is the first item.

@@item
This is the second item.
@@end enumerate


@@node First Section
@@section First Section

First section of first chapter.


@@node Second Section
@@section Second Section

Second section of first chapter.
@end group
@end example

In the Info output, the @samp{First Chapter} node will contain a
menu listing the two sections in the chapter.  Similarly, when this
node is output in its own HTML file, it will contain a table of contents
for the chapter.

Here is what the contents of this chapter will look like:

@sp 1
@need 700
@quotation
@chapheading 1. First Chapter

This is the first chapter.

Here is a numbered list.

@enumerate
@item
This is the first item.

@item
This is the second item.
@end enumerate

@heading 1.1 First Section

First section of first chapter.

@heading 1.2 Second Section

Second section of first chapter.
@end quotation

@noindent (In the Info and HTML output, the chapter would also be split
into nodes.)


@node Ending a File
@nodedescription What is at the end of a Texinfo file?
@section Ending a Texinfo File
@cindex Ending a Texinfo file
@cindex Texinfo file ending
@cindex File ending

The end of a Texinfo file should include commands to create indices
(@pxref{Printing Indices & Menus}), and the @code{@@bye} command to mark
the last line to be processed.  For example:

@example
@@node Index
@@unnumbered Index

@@printindex cp

@@bye
@end example

@findex bye
@anchor{File End}
A @code{@@bye} command terminates Texinfo processing.  It should be on
a line by itself.  Anything following @code{@@bye} is completely
ignored.


@node Nodes
@nodedescription Writing nodes, the basic unit of Texinfo.
@chapter Nodes
@anchor{node}@anchor{@@node} @c old names

@cindex Node, defined
A @dfn{node} is a region of text that begins at a @code{@@node}
command, and continues until the next @code{@@node} command.
To specify a node, write a @code{@@node} command at the beginning of
a line, and follow it with the name of the node.
Info readers display one node at a time, and provide commands for the
user to move to related nodes.  The HTML output can be similarly navigated.

Nodes are used as the targets of cross-references.  Cross-references,
such as the one at the end of this sentence, are made with @code{@@xref}
and related commands; see @ref{Cross References}.  Cross-references can
be sprinkled throughout the text.  Other @@-commands may also
be the target of cross-references (@pxref{@code{@@anchor}}, @pxref{Floats}).

Normally, you put a node command immediately before each chapter
structuring command---for example, an @code{@@section} or
@code{@@subsection} line.  (@xref{Chapter Structuring}.)
You should do this even if you do not intend to format the file for Info.
This is because printed output uses both @code{@@node} names and
chapter-structuring names in the output for cross-references.  The only
time you are likely to use the chapter structuring commands without also
using nodes is if you are writing a document that contains no cross
references and will only be printed, not transformed into Info, HTML, or
other formats.


@node Writing a Node
@nodedescription How to write a @code{@@node} line.
@section Writing a @code{@@node} Line
@cindex Writing a @code{@@node} line
@cindex @code{@@node} line writing
@cindex Node line writing

@findex node
Write @code{@@node} at the beginning of a line followed by the name of 
the node, like this:

@example
@@node @var{node-name}
@end example

After you have inserted a @code{@@node} line, you should immediately
write the @@-command for the associated chapter or section (if any)
and insert its name.

You may optionally follow the node name argument to @code{@@node}
with up to three optional arguments on the rest of the same line,
separating the arguments with commas.  These are the names of the
`Next', `Previous', and `Up' pointers, in that order.  Hence,
the template for a fully-written-out node line with `Next', `Previous',
and `Up' pointers looks like this:

@example
@@node @var{node-name}, @var{next}, @var{previous}, @var{up}
@end example

The @var{node-name} argument must be present, but the others are
optional.  If you wish to specify some but not others, just insert
commas as needed, as in: @samp{@@node mynode,,,uppernode}.
Any spaces before or after each name on the @code{@@node} line are
ignored.  However, if your Texinfo document is hierarchically organized,
as virtually all are, we recommend leaving off all the pointers and 
letting @code{texi2any} determine them.

@cindex Creating pointers with @code{texi2any}
@cindex Pointer creation with @code{texi2any}
@cindex Automatic pointer creation with @code{texi2any}
@cindex Implicit pointer creation with @code{texi2any}
The @code{texi2any} program automatically determines node pointers
for a hierarchically organized document.  For it to do this, each
@code{@@node} command should be followed immediately by a sectioning
command such as @code{@@chapter} or @code{@@section} (except that
comment lines may intervene).  Finally, you must follow the `Top'
@code{@@node} line with a line beginning with @code{@@top} to mark
the top-level node in the file.  @xref{@code{@@top} Command}.

Even when you explicitly specify all pointers, you cannot write the
nodes in the Texinfo source file in an arbitrary order.
You must write the nodes in the order you wish them to appear in the 
output.  For Info format one can imagine that the order may not matter, 
but it matters for the other formats.

In most cases, you will want to take advantage of the pointer creation 
feature, and not redundantly specify node pointers that the programs can 
determine.
However, Texinfo documents are not required to be organized
hierarchically or in fact to contain sectioning commands at all (for
example, if you never intend the document to be printed), so node
pointers may still be specified explicitly, in full generality.

If you are using GNU Emacs, and want explicit pointers, you can use the
update node commands provided by Texinfo mode to insert the names of
the pointers.  (@xref{Updating Nodes and Menus}.)

Alternatively, you can insert the `Next', `Previous', and `Up'
pointers yourself.  If you do this in Emacs, you may find it helpful
to use the Texinfo mode keyboard command @kbd{C-c C-c n}.  This command
inserts @samp{@@node} and a comment line listing the names of the
pointers in their proper order.  The comment line helps you keep track
of which arguments are for which pointers.


@node Node Names
@nodedescription How to choose node names.
@section Choosing Node Names

@cindex Node names, choosing
The name of a node identifies the node.  For all the details of node
names, @pxref{Node Line Requirements}).

@anchor{Node Line Tips}@c previous node name
Here are some suggestions for node names:

@itemize @bullet
@item
Try to pick node names that are informative but short.

In the Info file, the file name, node name, and pointer names are all
inserted on one line, which may run into the right edge of the window.
(This does not cause a problem with Info, but is ugly.)

@item
Try to pick node names that differ from each other near the beginnings
of their names.  This way, it is easy to use automatic name completion in
Info.

@item
Conventionally, node names are capitalized in the same way as section
and chapter titles.  In this manual, initial and significant words are
capitalized; others are not.  In other manuals, just initial words and
proper nouns are capitalized.  Either way is fine; we recommend just
being consistent.

@item
Node names should not contain user-defined macros.  @xref{Macro Details}
for other constraints on the use of macros.

@item
In HTML output, any characters in the node name other than plain ASCII 
letters, numbers or spaces will be changed in the file name.  
(@xref{HTML Xref Node Name Expansion}.)
This can make the URLs for the pages in your manual less user-friendly;
for example, in this manual the @samp{@@dots} node is output as
@file{__0040dots.html}.
@end itemize

Because node names are used in cross-references, it is not desirable to
casually change them once published.  When you delete or rename a node, it is
usually a good idea to define an @code{@@anchor} with the old name.
That way, references from other manuals, from mail archives, and so on
are not invalidated.  @xref{@code{@@anchor}}.

The pointers from a given node enable you to reach other nodes and
consist simply of the names of those nodes.

Normally, a node's `Up' pointer contains the name of the node whose
menu mentions that node.  The node's `Next' pointer contains the name
of the node that follows the present node in that menu and its
`Previous' pointer contains the name of the node that precedes it in
that menu.  When a node's `Previous' node is the same as its `Up'
node, both pointers name the same node.

Usually, the first node of a Texinfo file is the `Top' node, and its
`Up' pointer points to the @file{dir} file, which contains the main menu
for all of Info.


@node Node Line Requirements
@nodedescription Keep names unique.
@section @code{@@node} Line Requirements

@cindex Node line requirements
@cindex Restrictions on node names

Names used with @code{@@node} have several requirements:

@itemize @bullet
@item
@cindex Unique node names requirement
@cindex Node names must be unique
All the node names in a single Texinfo file must be unique.

This means, for example, that if you end every chapter with a summary,
you must name each summary node differently.  You cannot just call
them all ``Summary''.  You may, however, duplicate the titles of
chapters, sections, and the like.  Thus you can end each chapter with
a section called ``Summary'', so long as the node names for those
sections are all different.

Node names, anchor names (@pxref{@code{@@anchor}}),
and float labels (@pxref{@code{@@float}}) must all be unique.

@item
@cindex Commands in node names
@cindex @sortas{at} @@-commands @subentry in node names
Node names can contain @@-commands@footnote{Prior to the Texinfo 5 release in 2013, this feature was supported in
an ad hoc way (the @option{--commands-in-node-names} option to
@command{makeinfo}).  Now it is part of the language.
}.  For example, using
@code{@@TeX@{@}} in a node name results in the @TeX{} logo being
output, as it would be in normal text.  Cross-references should
use @code{@@TeX@{@}} just as the node name does.

Some commands do not make sense in node names; for instance,
environments (e.g., @code{@@quotation}), commands that read a whole
line as their argument (e.g., @code{@@sp}), and plenty of others.
For the complete list of commands that are allowed, and their
expansion for HTML identifiers and file names, @pxref{HTML Xref
Command Expansion}.

@item
@cindex Parentheses in node name
A node name may not start with a left parenthesis preceding a right
parenthesis, as in @code{(not)allowed}, since this syntax is used to
specify an external manual.

@item
@cindex Colon in node name
@cindex Comma in node name
@cindex Period in node name
@cindex Characters, invalid in node name
@cindex Invalid characters in node names
@cindex Node names, invalid characters in
@anchor{Info Node Names Constraints}
Unfortunately, you cannot reliably use periods, commas, or colons
within a node name; these can confuse some Info readers.
@command{texi2any} quotes problematic node names and labels by default,
but some Info readers do not recognize this syntax.  Node name and label
quoting causes @code{DEL} characters (@samp{CTRL-?}, character number 127,
often rendered as @samp{^?}) to appear around the name.  To remove
node names and labels quoting, you can set the customization variable
@code{INFO_SPECIAL_CHARS_QUOTE} to @samp{0} (@pxref{Info and Plaintext
Customization Variables}).

@command{texi2any} warns about such problematic usage in node names,
menu items, and cross-references.  If you don't want to see the
warnings, you can set the customization variable
@code{INFO_SPECIAL_CHARS_WARNING} to @samp{0} (@pxref{Info and Plaintext
Customization Variables}).

If you insist on using these characters in node names, in order not
to confuse the Texinfo processors you must still escape those characters,
by using either special insertions (@pxref{Inserting a Comma}) or @code{@@asis}
(@pxref{@code{@@asis}}).  For example:

@example
@@node foo@@asis@{::@}bar@@comma@{@} baz
@end example

As an example of avoiding the special characters, the following is a
section title in this manual:

@example
@@section @@code@{@@@@unnumbered@}, @@code@{@@@@appendix@}: Chapters with@enddots{}
@end example

@noindent
But the corresponding node name lacks the commas and the subtitle:

@example
@@node @@code@{@@@@unnumbered @@@@appendix@}
@end example

@cindex Case in node name
@item
Case is significant in node names.

@cindex White space in node name
@cindex Spaces in node name
@item
Spaces before and after names on the @samp{@@node} line are ignored.
Multiple whitespace characters ``inside'' a name are collapsed to a
single space.  For example:

@example
@@node foo bar
@@node  foo bar,
@@node foo bar ,
@@node foo  bar,
@@node  foo  bar ,
@end example

@c Consistently with the HTML Cross-reference Node Name Expansion
@c spaces and newlines generated by @-commands should also be
@c collapsed to a single space.  If we wanted to be explicit, we
@c could have added a line corresponding to
@c @node @  foo @: @* bar,
@c However, it is best to leave those special cases non documented

@noindent all define the same node, namely @samp{foo bar}.
@c FIXME to be removed.  In 2022 both Info readers find the node.
In menu entries, a single internal space should be used in node
names or some versions of some Info readers will not find the node.
@end itemize


@node First Node
@nodedescription How to write a `Top' node.
@section The First Node
@cindex Top node is first
@cindex First node

The first node of a Texinfo file is the @dfn{Top} node, except in an
included file (@pxref{Include Files}).  The Top node should contain
a short summary and a master menu.  @xref{The Top Node} for more
information on the Top node contents and examples.  Straight text
before the Top node outside of any node should be avoided.  Such
text, if present, is not output for DocBook.


Here is a description of the node pointers to be used in the Top node:

@itemize @bullet
@item
@cindex Up node of Top node
@cindex (dir) as Up node of Top node
The Top node (which must be named @samp{top} or @samp{Top}) should have
as its `Up' node the name of a node in another file, where there is a
menu that leads to this file.  Specify the file name in parentheses.

Usually, all Info files are available through a single virtual Info
tree, constructed from multiple directories.  In this case, use
@samp{(dir)} as the parent of the Top node; this specifies the
top-level node in the @file{dir} file, which contains the main menu
for the Info system as a whole.  (Each directory with Info files is
intended to contain a file named @file{dir}.)

That's fine for Info, but for HTML output, one might well want the Up
link from the Top node to go to some specific place.
For example, for GNU the natural place would be
@url{https://www.gnu.org/manual/} (a web page collecting links to most
GNU manuals), better specified as just @code{/manual/} if the manual
will be installed on @code{www.gnu.org}.  This can be specified with
the @code{TOP_NODE_UP_URL} customization variable (@pxref{File Names
and Links Customization for HTML}), as in

@example
$ @kbd{texi2any --html -c TOP_NODE_UP_URL=/manual/} ...
@end example

@c the following line is not true anymore
@c All links to @code{(dir)} will be replaced by the given url.

@item
@cindex Prev node of Top node
The `Prev' node of the Top node is usually omitted.

@item
@cindex Next node of Top node
The `Next' node of the Top node should be the first chapter in your
document.

@end itemize

@xref{Installing an Info File}, for more information about installing
an Info file in the @file{info} directory.

It is usually best to leave the pointers off entirely and let the
tools implicitly define them, with this simple result:

@example
@@node Top
@end example


@node @code{@@top} Command
@nodedescription How to use the @code{@@top} command.
@section The @code{@@top} Sectioning Command

@anchor{top command}@c old name
@anchor{makeinfo top}@c another old name
@anchor{makeinfo top command}@c yet another name
@findex top

The @code{@@top} command is a special sectioning command that you
should only use after a @samp{@@node Top} line at the beginning of a
Texinfo file.

It produces the same sort of output as @code{@@unnumbered}
(@pxref{@code{@@unnumbered @@appendix}}).  In @LaTeX{} @code{\part*} is used.

@code{@@top} is ignored when raising or lowering sections.  That is,
it is never lowered and nothing can be raised to it
(@pxref{Raise/lower sections}).

It used to be conventional to wrap the @samp{Top} node
in an @code{@@ifnottex} conditional so that it would not appear in 
printed output (@pxref{Conditionals}).  Thus, a Top node often looked
like this:

@example
@@ifnottex
@@node Top
@@top @var{your-manual-title}

@var{very-high-level-summary}
@@end ifnottex
@end example

This is no longer necessary, as the @samp{Top} node is now never output 
for printed output.  The @samp{Top} node is not output for DocBook either.


@node Texinfo Document Structure
@nodedescription Double structure of documents.
@section Texinfo Document Structure
@cindex Texinfo document structure
@cindex Document structure, of Texinfo
@cindex Structure, of Texinfo documents
@cindex Double structure, of Texinfo documents

@anchor{Two Paths}@c old node name

Nodes can contain @dfn{menus}, which contain the names of @dfn{child
nodes} within the parent node; for example, a node corresponding to a
chapter would have a menu of the sections in that chapter.  The menus
allow the user to move to the child nodes in the Info output.

In addition, nodes contain @dfn{node pointers} that name other nodes.
The `Next' and `Previous' pointers link nodes at the same sectioning
level into a chain.  As you might imagine, the `Next' pointer links to
the next node, and the `Previous' pointer links to the previous node.
In general, `Next' and `Previous' refer to nodes at the @emph{same
hierarchical level} in the manual, not necessarily to the next node
within the Texinfo file.  In the Texinfo file, the subsequent node may
be at a lower level---a section-level node most often follows a chapter-level
node, for example.
Thus, for example, all the nodes that are at the level of sections
within a chapter are linked together, and the order in this chain
is the same as the order of the children in the menu of the parent
chapter.  Each child node records the parent node name as its `Up'
pointer.

Since the `Top' node is the only node at that level, `Next'
refers to the first following node, which is almost always a chapter
or chapter-level node.  This is an exception to the rule of
`Next' being at the same hierarchical level.

@cindex @code{accesskey} @subentry in HTML output of nodes
The Info and HTML output for each node includes links to the
`Next', `Previous', and `Up' nodes.  The HTML also uses
the @code{accesskey} attribute with the values @samp{n}, @samp{p}, and
@samp{u} respectively.  This allows people using web browsers to
follow the navigation using (typically) @kbd{M-@var{letter}}, e.g.,
@kbd{M-n} for the `Next' node, from anywhere within the node.
Node pointers and menus provide structure for Info files just as
chapters, sections, subsections, and the like provide structure for
printed books.  The two structures are theoretically distinct; in
practice, however, the tree structure of printed books is essentially
always used for the node and menu structure also, as this leads to a
document which is easy to follow.

Typically, the sectioning structure and the node structure are
completely parallel, with one node for each chapter, section, etc.,
and with the nodes following the same hierarchical arrangement as the
sectioning.  Thus, if a node is at the logical level of a chapter, its
child nodes are at the level of sections; similarly, the child nodes
of sections are at the level of subsections.

It is technically possible to create Texinfo documents with
only one structure or the other, or for the two structures not to be
parallel, or for either the sectioning or node structure to be
different from the conventional structure.  To the best of our
knowledge, however, all the Texinfo manuals currently in general use do
follow the conventional parallel structure.


@node Node Menu Illustration
@nodedescription A diagram, and sample nodes and menus.
@section Node and Menu Illustration

Here is a diagram that illustrates a Texinfo file with three chapters,
each of which contains two sections.

The ``root'' is at the top of the diagram and the ``leaves'' are at
the bottom.  This is how such a diagram is drawn conventionally; it
illustrates an upside-down tree.  For this reason, the root node is
called the `Top' node, and `Up' node pointers carry you closer to the
root.

@example
@group
                         Top
                          |
        -------------------------------------
       |                  |                  |
    Chapter 1          Chapter 2          Chapter 3
       |                  |                  |
    --------           --------           --------
   |        |         |        |         |        |
Section  Section   Section  Section   Section  Section
  1.1      1.2       2.1      2.2       3.1      3.2
@end group
@end example

Using explicit pointers (not recommended, but shown for purposes
of the example), the fully-written command to start Chapter@tie{}2
would be this:

@example
@group
@@node     Chapter 2,  Chapter 3, Chapter 1, Top
@@comment  node-name,  next,      previous,  up
@end group
@end example

@noindent
This @code{@@node} line says that the name of this node is
``Chapter@tie{}2'', the name of the `Next' node is ``Chapter 3'', the
name of the `Previous' node is ``Chapter@tie{}1'', and the name of the
`Up' node is ``Top''.  You can (and should) omit writing out these
node names if your document is hierarchically organized, but the 
pointer relationships still obtain.

To go to Sections 2.1 and 2.2 using Info, you need a menu inside
Chapter 2.  (@xref{Menus}.)  You would write the menu just before the
beginning of Section 2.1, like this:

@example
@group
   @@menu
   * Sect. 2.1::    Description of this section.
   * Sect. 2.2::    Description.
   @@end menu
@end group
@end example

The automatic pointers for the node for Sect.@: 2.1 correspond to:

@example
@group
@@node     Sect. 2.1, Sect. 2.2, ,         Chapter 2
@@comment  node-name, next,      previous, up
@end group
@end example

Note that no `Prev' pointer is generated, since there is
no other node at the same hierarchical level before Sect.@: 2.1.

Using explicit pointers, the node for Sect.@: 2.1 could be written like this:

@example
@group
@@node     Sect. 2.1, Sect. 2.2, Chapter 2, Chapter 2
@@comment  node-name, next,      previous,  up
@end group
@end example

With automatic pointers, the `Next' and `Previous' pointers of a node
lead to other nodes at the same level---from chapter to chapter or
from section to section.  As shown, when using explicit pointers, 
the pointers can also lead somewhere else, here, for
example, the `Previous' pointer points up.  An `Up' pointer usually
leads to a node at the level above (closer to the `Top' node; and a
`Menu' leads to nodes at a level below (closer to `leaves').
(A cross-reference can point to a node at any level; see
@ref{Cross References}.)

Technically, explicit node pointers can carry you to any node,
regardless of the structure of the document; even to nodes in a
different Info file.  However, it would be very confusing for readers
to have the `Next', `Previous' and `Up' pointers lead to nodes that
do not correspond, even loosely, to the next, previous and up node.

A @code{@@node} command and a chapter structuring command are
conventionally used together, in that order, often followed by
indexing commands.  (As shown in the example above, you may follow the
@code{@@node} line with a comment line, e.g., to show which pointer is
which if explicit pointers are used.)  The Texinfo processors use this
construct to determine the relationships between nodes and sectioning
commands.

Here is the beginning of the chapter in this manual called ``Ending a
Texinfo File''.  This shows a @code{@@node} line followed by a
@code{@@chapter} line, and then by indexing lines.

@example
@group
@@node Ending a File
@@chapter Ending a Texinfo File
@@cindex Ending a Texinfo file
@@cindex Texinfo file ending
@@cindex File ending
@end group
@end example


@node Node Descriptions
@nodedescriptionblock
@code{@@nodedescription} and @code{@@nodedescriptionblock}.
@end nodedescriptionblock
@section Node Descriptions

@findex nodedescription
You can provide a short description of the purpose of a node by using
the @code{@@nodedescription} command following the @code{@@node} line.
Such a description might elaborate on or extend the information in the
node name itself.

@findex nodedescriptionblock
You can also use a @code{@@nodedescriptionblock} environment to
provide a node description. This may be useful for longer descriptions.

@command{texi2any} uses the content you provide with these commands
when outputting menus for Info output format (and, optionally,
for HTML).  @command{texi2any} uses the description after a menu
entry for the node if it is generating the menu automatically, or
if no description for the menu entry was provided in an explicit
@code{@@menu} block. (@xref{Menus}).

Here is an example of using these commands:

@example
@@node Tools
@@chapter Tools

This chapter is on different tools you can use.

@@node Screwdrivers
@@nodedescription Flathead and Phillips.
@@section Screwdrivers

This section is about screwdrivers.

@@node Drills
@@nodedescriptionblock
Making holes in things with power screwdrivers, drill drivers, combi
drills, impact drivers, hammer drills, breakers and demolition drills.
@@end nodedescriptionblock
@@section Drills

This section is about drills.
@end example

In Info output, @command{texi2any} would output the @samp{Tools} node with
a menu as follows:

@example
* Menu:

* Screwdrivers::          Flathead and Phillips.
* Drills::                Making holes in things with power
                          screwdrivers, drill drivers, combi
                          drills, impact drivers, hammer drills,
                          breakers and demolition drills.
@end example


@node Menus
@nodedescription Listing subordinate nodes.
@section Menus
@cindex Menus
@findex menu

@dfn{Menus} contain pointers to subordinate nodes.  In Info output,
you use menus to go to such nodes.  @command{texi2any} can output menus in
HTML output, but does not do so by default
(@pxref{HTML Output Structure Customization}, @code{FORMAT_MENU}).
Menus have no role in printed manuals or other output formats.

Menus are automatically generated by @command{texi2any} when outputting
Info or HTML with menus for nodes followed by a sectioning command, without an
explicit @code{@@menu} block, and with automatic pointers.

It is often more convenient to let @command{texi2any} generate
menus for you, as you do not then have the burden of updating menu
blocks in your Texinfo source when you add, remove, or relocate nodes.
In the usual case of a hierarchically organized manual with sectioning
commands associated with nodes, and with node pointers left out, you
should only write menus if you want exact control over the contents
and formatting of menus in Info.


@node Writing a Menu
@nodedescription What is a menu?
@subsection Writing a Menu
@cindex Writing a menu
@cindex Menu writing

A menu consists of a @code{@@menu} command on a line by itself,
followed by menu entry lines or menu comment lines, and then followed
by an @code{@@end menu} command on a line by itself.

A menu looks like this:

@example
@group
@@menu
Larger Units of Text

* Files::                       All about handling files.
* Multiples: Buffers.           Multiple buffers; editing
                                 several files at once.
@@end menu
@end group
@end example

@cindex Spaces, in menus
In a menu, every line that begins with an @w{@samp{* }} is a @dfn{menu
entry}.  (Note the space after the asterisk.)  In the example above,
the two lines starting with @w{@samp{* }} are menu entries.

@cindex Menu comment
A line that does not start with an @w{@samp{* }} may also appear in a
menu.  Such a line is not a menu entry but rather a @dfn{menu comment}
line.   In the example above, the line @samp{Larger Units of Text}
is a menu comment line.  Menu comment lines and any empty lines are kept
in the output.

@cindex Hierarchical documents, and menus
Technically, menus can carry you to any node, regardless of the
structure of the document; even to nodes in a different Info file.
However, the @command{texi2any} implicit pointer creation feature
(@pxref{Writing a Node}) and GNU Emacs Texinfo mode updating commands
work only to create menus of subordinate nodes in a hierarchically
structured document.  In a hierarchically structured document, it is
much better to use cross-references to refer to arbitrary nodes.

In Info, a user selects a node with the @kbd{m} (@code{Info-menu})
command.  The menu entry name is what the user types after the @kbd{m}
command.
@cindex @code{accesskey} @subentry in HTML output of menus
In the HTML output, the @code{accesskey} attribute is used with the
values @samp{1}@dots{}@samp{9} for the first nine entries.  This
allows people using web browsers to follow the first menu entries
using (typically) @kbd{M-@var{digit}}, e.g., @kbd{M-1} for the first
entry.


@node Menu Example
@nodedescription Two and three part menu entries.
@subsection A Menu Example
@cindex Menu example
@cindex Example menu

@c merge with Writing a Menu node?

A menu looks like this in Texinfo:

@example
@group
@@menu
* menu entry name: Node name.   A short description.
* Node name::                   This form is preferred.
@@end menu
@end group
@end example

@need 800
@noindent
This produces:

@example
@group
* Menu:

* menu entry name: Node name.   A short description.
* Node name::                   This form is preferred.
@end group
@end example

@need 700
Here is an example as you might see it in a Texinfo file:

@example
@group
@@menu
Larger Units of Text

* Files::                       All about handling files.
* Multiples: Buffers.           Multiple buffers; editing
                                 several files at once.
@@end menu
@end group
@end example

@need 800
@noindent
This produces:

@example
@group
* Menu:
Larger Units of Text

* Files::                       All about handling files.
* Multiples: Buffers.           Multiple buffers; editing
                                 several files at once.
@end group
@end example

In this example, the menu has two entries.  @samp{Files} is both a menu
entry name and the name of the node referred to by that name.
@samp{Multiples} is the menu entry name; it refers to the node named
@samp{Buffers}. The line @samp{Larger Units of Text} is a comment; it
appears in the menu, but is not an entry.

Since no file name is specified with either @samp{Files} or
@samp{Buffers}, they must be the names of nodes in the same Info file
(@pxref{Other Info Files, , Referring to Other Info Files}).


@node Menu Location
@nodedescription Menus go at the ends of nodes.
@subsection Menu Location
@cindex Menu location
@cindex Location of menus

There may be at most one menu in a node.  A menu is conventionally
located at the end of a node, without any regular text or additional
commands between the @code{@@end menu} and the beginning of the next
node.

@cindex Info format, and menus
This convention is useful, since a reader who uses the menu could
easily miss any such text.  Also, any such post-menu text will be
considered part of the menu in Info output (which has no marker for
the end of a menu).  Thus, a line beginning with @samp{* } will likely
be incorrectly handled.

It's usually best if a node with a menu does not contain much text.
If you find yourself with a lot of text before a menu, we generally
recommend moving all but a couple of paragraphs into a new subnode.
Otherwise, it is easy for readers to miss the menu.


@node Menu Parts
@nodedescription A menu entry has three parts.
@subsection The Parts of a Menu
@cindex Parts of a menu
@cindex Menu parts
@cindex @code{@@menu} parts

A menu entry has three parts, only the second of which is required:

@enumerate
@item
The menu entry name (optional).

@item
The name of the node (required).

@item
A description of the item (optional).
@end enumerate

The template for a generic menu entry looks like this (but see the
next section for one more possibility):

@example
* @var{menu-entry-name}: @var{node-name}.   @var{description}
@end example

Follow the menu entry name with a single colon, and follow the node
name with tab, comma, newline, or the two characters period and space
(@samp{. }).

The third part of a menu entry is a descriptive phrase or sentence.
Menu entry names and node names are often short; the description
explains to the reader what the node is about.  A useful description
complements the node name rather than repeats it.  The description,
which is optional, can spread over multiple lines; if it does, some
authors prefer to indent the second line while others prefer to align
it with the first (and all others).  It's up to you.  An empty line,
or the next menu entry, ends a description.

Space characters in a menu are preserved as-is in the Info output; this
allows you to format the menu as you wish.
@c FIXME to be removed.  In 2022 both Info readers find the node.
Unfortunately you must type
node names without any extra spaces or some versions of some Info
readers will not find the node (@pxref{Node Line Requirements}).

@command{texi2any} warns and protect names when the text of a menu item
(and node names and cross-references) contains a problematic construct that
could interfere with its parsing in Info.  @xref{Info Node Names Constraints}.


@node Less Cluttered Menu Entry
@nodedescription Two part menu entry.
@subsection Less Cluttered Menu Entry
@cindex Two part menu entry
@cindex Double-colon menu entries
@cindex Menu entries with two colons
@cindex Less cluttered menu entry
@cindex Uncluttered menu entry

When the menu entry name and node name are the same, you can write
the name immediately after the asterisk and space at the beginning of
the line and follow the name with two colons.

@need 800
For example, write

@example
* Name::                        @var{description}
@end example

@need 800
@noindent
instead of

@example
* Name: Name.                   @var{description}
@end example

We recommend using the node name for the menu entry name whenever
possible, since it reduces visual clutter in the menu.


@node Other Info Files
@nodedescription How to refer to a different Info file.
@subsection Referring to Other Info Files
@cindex Referring to other Info files
@cindex Nodes in other Info files
@cindex Other Info files' nodes
@cindex Going to other Info files' nodes
@cindex Info; other files' nodes

You can create a menu entry that enables a reader in Info to go to a
node in another Info file by writing the file name in parentheses just
before the node name.  Some examples:

@example
@group
@@menu
* @var{first-entry-name}:(@var{filename})@var{nodename}.     @var{description}
* (@var{filename})@var{second-node}::                  @var{description}
@@end menu
@end group
@end example

For example, to refer directly to the @samp{Outlining} and
@samp{Rebinding} nodes in the @cite{Emacs Manual}, you could write a
menu like this:

@example
@group
@@menu
* Outlining: (emacs)Outline Mode. The major mode for
                                   editing outlines.
* (emacs)Rebinding::              How to redefine the
                                   meaning of a key.
@@end menu
@end group
@end example

If you do not list the node name, but only name the file, then Info
presumes that you are referring to the `Top' node.  Examples:

@example
@group
* Info: (info).         Documentation browsing system.
* (emacs)::             The extensible, self-documenting
                         text editor.
@end group
@end example

The GNU Emacs Texinfo mode menu updating commands only work with nodes
within the current buffer, so you cannot use them to create menus that
refer to other files.  You must write such menus by hand.
@xref{Updating Nodes and Menus}.


@node Chapter Structuring
@nodedescription Creating chapters, sections, appendices, etc.
@chapter Chapter Structuring
@anchor{Structuring}@c old name
@cindex Chapter structuring
@cindex Structuring of chapters
@cindex Sectioning

Texinfo's @dfn{chapter structuring} commands divide a document into a
hierarchy of chapters, sections, subsections, and subsubsections.  These
commands generate large headings in the text, like the one above.  They
also provide information for generating the table of contents
(@pxref{Contents,, Generating a Table of Contents}).

Normally you put a @code{@@node} command immediately before each
chapter structuring command.  @xref{Nodes}.


@node Tree Structuring
@nodedescription A manual is like an upside down tree @dots{}
@section Tree Structure of Sections
@cindex Tree structuring

A Texinfo file is usually structured like a book with chapters,
sections, subsections, and the like.  This structure can be visualized
as a tree (or rather as an upside-down tree) with the root at the top
and the levels corresponding to chapters, sections, subsection, and
subsubsections.

Here is a diagram that shows a Texinfo file with three chapters, each
with two sections.

@example
@group
                         Top
                          |
        -------------------------------------
       |                  |                  |
    Chapter 1          Chapter 2          Chapter 3
       |                  |                  |
    --------           --------           --------
   |        |         |        |         |        |
Section  Section   Section  Section   Section  Section
  1.1      1.2       2.1      2.2       3.1      3.2

@end group
@end example

In a Texinfo file that has this structure, the beginning of Chapter 2
would be written like this:

@example
@group
@@node    Chapter 2
@@chapter Chapter 2
@end group
@end example

@noindent
For purposes of example, here is how it would be written with
explicit node pointers:

@example
@group
@@node    Chapter 2,  Chapter 3, Chapter 1, Top
@@chapter Chapter 2
@end group
@end example

The chapter structuring commands are described in the sections that
follow; the @code{@@node} command is described in
the previous chapter (@pxref{Nodes}).


@node Structuring Command Types
@section Structuring Command Types

The chapter structuring commands fall into four groups, each of which
contains structuring commands at the levels of chapters, sections,
subsections, and subsubsections:

@itemize @bullet
@item
The @code{@@chapter}-like commands and @code{@@appendix}-like commands
produce numbered or lettered entries both in the body of a document and
in its table of contents.

@item
The @code{@@unnumbered}-like commands produce unnumbered entries
both in the body of a document and in its table of contents.  The
@code{@@top} command, which has a special use, is a member of this
group (@pxref{@code{@@top} Command}).  An @code{@@unnumbered} section
is a normal part of the document structure.

@item
The @code{@@heading}-like commands produce simple unnumbered
headings that do not appear in a table of contents, are not associated
with nodes, and cannot be cross-referenced.  These heading commands
never start a new page.
@end itemize

In printed output, the chapter structuring commands produce headings
in the document.  When a @code{@@setchapternewpage} command says to do so, the
@code{@@chapter}, @code{@@unnumbered}, and @code{@@appendix} commands
start new pages in the printed manual; the @code{@@heading} commands
do not.  @xref{@code{@@setchapternewpage}}.

In Info and plain text output, the command causes the
title to appear on a line by itself, with a line of an ASCII character
(@samp{*}, @samp{=}, @dots{}) inserted underneath.
For example, the ``Chapter Structuring'' heading could be:

@example
@group
5 Chapter Structuring
*********************
@end group
@end example

@noindent The underlining character is the same for all the commands at the
same level.  For instance, it is the same for the chapter-level commands
@code{@@chapter}, @code{@@apppendix}, @code{@@unnumbered} and
@code{@@chapheading}.

In HTML, the chapter-level commands produce an @code{<h2>}-level
header by default (controlled by the @code{CHAPTER_HEADER_LEVEL}
customization variable, @pxref{HTML Customization of Specific Output}).
The heading element level is adjusted for the other commands.

In the DocBook output, the appropriate level of element is used.
The produced element includes all following sections up to the next command
at the same or higher level.
For example, a @code{<chapter>} element is produced for @code{@@chapter},
and contains any sections or subsections in the chapter.

Here is a summary:

@tex
{\globaldefs=1 \smallfonts \rm}
@end tex

@multitable @columnfractions .19 .30 .29 .22
@item                        @tab                              @tab                       @tab No new page
@item @i{Numbered}           @tab @i{Unnumbered}               @tab @i{Lettered/numbered} @tab @i{Unnumbered}
@item In contents            @tab In contents                  @tab In contents           @tab Not in contents
@item                        @tab @code{@@top}                 @tab                       @tab @code{@@majorheading}
@item @code{@@chapter}       @tab @code{@@unnumbered}          @tab @code{@@appendix} @tab @code{@@chapheading}
@item @code{@@section}       @tab @code{@@unnumberedsec}       @tab @code{@@appendixsec} @tab @code{@@heading}
@item @code{@@subsection}    @tab @code{@@unnumberedsubsec}    @tab @code{@@appendixsubsec} @tab @code{@@subheading}
@item @code{@@subsubsection} @tab @code{@@unnumberedsubsubsec} @tab @code{@@appendixsubsubsec} @tab @code{@@subsubheading}
@end multitable
@tex
{\globaldefs=1 \textfonts \rm}
@end tex


@node @code{@@chapter}
@section @code{@@chapter}: Chapter Structuring

@anchor{chapter}@c old name
@findex chapter

@code{@@chapter} identifies a chapter in the document--the highest
level of the normal document structuring hierarchy.  Write the command
at the beginning of a line and follow it on the same line by the title
of the chapter.  The chapter is numbered automatically, starting
from@tie{}1.

For example, the present chapter in this manual is entitled
``Chapter Structuring''; the @code{@@chapter} line
looks like this:

@example
@@chapter Chapter Structuring
@end example



@node @code{@@unnumbered @@appendix}
@section @code{@@unnumbered}, @code{@@appendix}: Chapters with Other Labeling

@anchor{unnumbered & appendix}@c old name
@findex unnumbered
@findex appendix

Use the @code{@@unnumbered} command to start a chapter-level element
that appears without chapter numbers of any kind.  Use the
@code{@@appendix} command to start an appendix that is labeled by
letter (`A', `B', @dots{}) instead of by number; appendices are also
at the chapter level of structuring.

Write an @code{@@appendix} or @code{@@unnumbered} command at the
beginning of a line and follow it on the same line by the title,
just as with @code{@@chapter}.

@findex centerchap
Texinfo also provides a command @code{@@centerchap}, which is analogous
to @code{@@unnumbered}, but centers its argument in the printed and HTML
outputs.  This kind of stylistic choice is not usually offered by
Texinfo.
@c but the Hacker's Dictionary wanted it, before they quit Texinfo.
You are recommended not to use this command, as
it may be removed in future releases of Texinfo.

@cindex DocBook and prefatory sections
@cindex Preface, etc., and DocBook
With @code{@@unnumbered}, if the name of the associated node is one of
these English words (case-insensitive):

@example
Acknowledgements  Colophon  Dedication  Preface
@end example

@cindex @code{<acknowledgements>} DocBook tag
@cindex @code{<colophon>} DocBook tag
@cindex @code{<dedication>} DocBook tag
@cindex @code{<preface>} DocBook tag
@cindex @code{<chapter>} DocBook tag
@noindent then the DocBook output uses corresponding special tags
(@code{<preface>}, etc.)@: instead of the default @code{<chapter>}.
The argument to @code{@@unnumbered} itself can be anything, and is
output as the element title as usual.


@node @code{@@majorheading @@chapheading}
@section @code{@@majorheading}, @code{@@chapheading}: Chapter-level Headings

@anchor{majorheading & chapheading}@c old name
@findex majorheading
@findex chapheading

The @code{@@majorheading} and @code{@@chapheading} commands produce
chapter-like headings in the body of a document.

However, neither command produces an entry in the table of contents,
and neither command causes @TeX{} to start a new page in a printed
manual.

In @TeX{}, a @code{@@majorheading} command generates a larger vertical
whitespace before the heading than a @code{@@chapheading} command but
is otherwise the same.

In other output formats, the @code{@@majorheading} and @code{@@chapheading}
commands produce a similar output to @code{@@chapter}.  The difference is
the lack of numbering and the lack of any association with nodes.
@xref{@code{@@chapter}}.


@node @code{@@section}
@section @code{@@section}: Sections Below Chapters

@anchor{section}@c old name
@findex section

An @code{@@section} command identifies a section within a chapter
unit, whether created with @code{@@chapter}, @code{@@unnumbered}, or
@code{@@appendix}, following the numbering scheme of the chapter-level
command.  Thus, within a @code{@@chapter} chapter numbered `1', the
sections are numbered `1.1', `1.2', etc.; within an @code{@@appendix}
``chapter'' labeled `A', the sections are numbered `A.1', `A.2', etc.;
within an @code{@@unnumbered} chapter, the section gets no number.

To make a section, write the @code{@@section} command at the
beginning of a line and follow it on the same line by the section
title.  For example:

@example
@@section This is a section
@end example

Section titles are listed in the table of contents.


@node @code{@@unnumberedsec @@appendixsec @@heading}
@section @code{@@unnumberedsec}, @code{@@appendixsec}, @code{@@heading}

@anchor{unnumberedsec appendixsec heading}@c old name
@findex unnumberedsec
@findex appendixsec
@findex heading

The @code{@@unnumberedsec}, @code{@@appendixsec}, and @code{@@heading}
commands are, respectively, the unnumbered, appendix-like, and
heading-like equivalents of the @code{@@section} command (see the
previous section).

@code{@@unnumberedsec} and @code{@@appendixsec} do not need to be used
in ordinary circumstances, because @code{@@section} may also be used
within @code{@@unnumbered} and @code{@@appendix} chapters; again, see
the previous section.

@table @code
@item @@unnumberedsec
The @code{@@unnumberedsec} command may be used within an unnumbered
chapter or within a regular chapter or appendix to produce an
unnumbered section.

@findex appendixsection
@item @@appendixsec
@itemx @@appendixsection
@code{@@appendixsection} is a longer spelling of the
@code{@@appendixsec} command; the two are synonymous.

Conventionally, the @code{@@appendixsec} or @code{@@appendixsection}
command is used only within appendices.

@item @@heading
You may use the @code{@@heading} command (almost) anywhere for a
section-style heading that will not appear in the table of contents.
The @code{@@heading}-series commands can appear inside most
environments, for example, though pathological and useless locations
such as an argument to another command, etc., are not allowed.

@end table


@node @code{@@subsection}
@section @code{@@subsection}: Subsections Below Sections

@anchor{subsection}@c old name
@findex subsection

Subsections are to sections as sections are to chapters;
@pxref{@code{@@section}}.  For example:

@example
@@subsection This is a subsection
@end example

Subsection titles are listed in the table of contents.


@node @code{@@unnumberedsubsec @@appendixsubsec @@subheading}
@section The @code{@@subsection}-like Commands

@anchor{unnumberedsubsec appendixsubsec subheading}@c old name
@findex unnumberedsubsec
@findex appendixsubsec
@findex subheading
@cindex Subsection-like commands

The @code{@@unnumberedsubsec}, @code{@@appendixsubsec}, and
@code{@@subheading} commands are, respectively, the unnumbered,
appendix-like, and heading-like equivalents of the @code{@@subsection}
command.  (@xref{@code{@@subsection}}.)

@code{@@unnumberedsubsec} and @code{@@appendixsubsec} do not need to
be used in ordinary circumstances, because @code{@@subsection} may
also be used within sections of @code{@@unnumbered} and
@code{@@appendix} chapters (@pxref{@code{@@section}}).

An @code{@@subheading} command produces a heading like that of a
subsection except that it is not numbered and does not appear in the
table of contents.  Similarly, an @code{@@unnumberedsubsec} command
produces an unnumbered heading like that of a subsection and an
@code{@@appendixsubsec} command produces a subsection-like heading
labeled with a letter and numbers; both of these commands produce
headings that appear in the table of contents.


@node @code{@@subsubsection}
@section @code{@@subsubsection} and Other Subsub Commands

@anchor{subsubsection}@c old name
@findex subsubsection
@findex unnumberedsubsubsec
@findex appendixsubsubsec
@findex subsubheading
@cindex Subsub sectioning commands

The fourth and lowest level sectioning commands in Texinfo are the
`subsub' commands.  They are:

@table @code
@item @@subsubsection
Subsubsections are to subsections as subsections are to sections.
(@xref{@code{@@subsection}}.)  Subsubsection titles appear in the
table of contents.

@item @@unnumberedsubsubsec
Unnumbered subsubsection titles appear in the table of contents,
but lack numbers.  Otherwise, unnumbered subsubsections are the same
as subsubsections.

@item @@appendixsubsubsec
Conventionally, appendix commands are used only for appendices and are
lettered and numbered appropriately.  They also appear in the table
of contents.

@item @@subsubheading
The @code{@@subsubheading} command may be used anywhere that you want
a small heading that will not appear in the table of contents.
@end table

As with subsections, @code{@@unnumberedsubsubsec} and
@code{@@appendixsubsubsec} do not need to be used in ordinary
circumstances, because @code{@@subsubsection} may also be used within
subsections of @code{@@unnumbered} and @code{@@appendix} chapters
(@pxref{@code{@@section}}).


@node @code{@@part}
@nodedescription Collections of chapters.
@section @code{@@part}: Groups of Chapters
@findex part
@cindex Part pages

The final sectioning command is @code{@@part}, to mark a @dfn{part} of
a manual, that is, a group of chapters or (rarely) appendices.  This
behaves quite differently from the other sectioning commands, to fit
with the way such ``parts'' are conventionally used in books.

No @code{@@node} command is associated with @code{@@part}.  Just write
the command on a line by itself, including the part title, at the
place in the document you want to mark off as starting that part.  For
example:

@example
@@part Part I:@@* The beginning
@end example

As can be inferred from this example, no automatic numbering or
labeling of the @code{@@part} text is done.  The text is taken as-is.

Because parts are not associated with nodes, no general text can
follow the @code{@@part} line.  To produce the intended output, it
must be followed by a chapter-level command (including its node).
Thus, to continue the example:

@example
@@part Part I:@@* The beginning

@@node Introduction
@@chapter Introduction
...
@end example

In the @TeX{} output, the @code{@@part} text is included in both the
normal and short tables of contents (@pxref{Contents}), without a page
number (since that is the normal convention).  In addition, a ``part
page'' is output in the body of the document, with just the
@code{@@part} text.  In the example above, the @code{@@*} causes a
line break on the part page (but is replaced with a space in the
tables of contents).  This part page is always forced to be on an odd
(right-hand) page, regardless of the chapter pagination
(@pxref{@code{@@setchapternewpage}}).  In the @LaTeX{} output,
the @code{@@part} is output as @code{\part}.

In the HTML output, the @code{@@part} text is similarly included in
the tables of contents, and a heading is included in the main document
text, as part of the following chapter or appendix node.

In the DocBook output, the @code{<part>} element includes all
the following chapters, up to the next @code{<part>}.  A @code{<part>}
containing chapters is also closed at an appendix.

In the Info and plain text output, @code{@@part} has no effect.

@code{@@part} is ignored when raising or lowering sections (see next
section).  That is, it is never lowered and nothing can be raised to it.


@node Raise/lower sections
@nodedescription How to change commands' hierarchical level.
@section Raise/lower Sections: @code{@@raisesections} and @code{@@lowersections}
@findex raisesections
@findex lowersections
@cindex Raising and lowering sections
@cindex Lowering and raising sections
@cindex Sections, raising and lowering

The @code{@@raisesections} and @code{@@lowersections} commands
implicitly raise and lower the hierarchical level of following
chapters, sections and the other sectioning commands (excluding parts).

That is, the @code{@@raisesections} command changes sections to
chapters, subsections to sections, and so on.  Conversely, the
@code{@@lowersections} command changes chapters to sections, sections
to subsections, and so on.  Thus, a @code{@@lowersections} command
cancels a @code{@@raisesections} command, and vice versa.

@cindex Include files, and section levels
As a practical matter, you generally only want to raise or lower large
chunks, usually in external files.
You can use @code{@@lowersections} to include text written as an outer
or standalone Texinfo file in another Texinfo file as an inner,
included file (@pxref{Include Files}).  Typical usage looks like this:

@example
@@lowersections
@@include somefile.texi
@@raisesections
@end example

@noindent (Without the @code{@@raisesections}, all the subsequent
sections in the main file would also be lowered.)

If the included file being lowered has a @code{@@top} node, you'll
need to conditionalize its inclusion with a flag (@pxref{@code{@@set
@@value}}).

Any menus in the final result have to take the raising and lowering
into account, so arbitrarily sprinkling @code{@@raisesections} and
@code{@@lowersections} commands throughout the document will likely
lead to errors (unless the menus in your document are all generated
automatically).

Repeated use of the commands continues to raise or lower the
hierarchical level a step at a time.  An attempt to raise above
`chapter' reproduces chapter commands; an attempt to lower below
`subsubsection' reproduces subsubsection commands.  Also, lowered
subsubsections and raised chapters will not work with
@command{texi2any}'s feature of implicitly determining node pointers,
since the menu structure cannot be represented correctly.

Write each @code{@@raisesections} and @code{@@lowersections} command
on a line of its own.


@node Unstructured Nodes
@nodedescription Nodes outside the main document structure.
@section Unstructured Nodes

@cindex Unstructured nodes
All the examples of nodes in this chapter so far have used a @code{@@node}
line followed by a structuring command (such as @code{@@chapter}).

@c @cindex Topic-oriented documentation
However, you can also create nodes without using a structuring command.
You may find this useful if you do not want your manual (or parts of
a manual) to have a hierarchical structure, with chapters superior to
sections, sections superior to sub-sections and so on.

@c comment this out until we know if we properly support this style
@c of documentation in Texinfo.
@c This unstructured
@c style of documentation is known as @dfn{topic-oriented documentation},
@c notably used by the DITA and Mallard systems.

To do this, follow the @code{@@node} line with one of the heading commands.
For example:

@example
@@node Topic
@@heading All about the Topic
@dots{}
@end example

The argument to the heading command will be printed as usual.  When
the @code{xrefautomaticsectiontitle} flag is on
(@pxref{@code{xrefautomaticsectiontitle}}), this argument will also be
used as the text for any cross-references to the node.

Such nodes are not part of a hierarchical document structure.  This means
that they are not listed in any table of contents, and automatic
node direction pointers (@samp{Next}, @samp{Prev} or @samp{Up};
@pxref{Writing a Node}) do not link to or from these nodes.

@findex xrefname
If you wish to create an unstructured node @emph{without} printing
a heading at the start, you can use the @code{@@xrefname} command in
place of the heading command.  For example:

@example
@@node Topic
@@xrefname All about the Topic
@dots{}
@end example

The @code{@@xrefname} command provides the text for cross-references to
the node when the @code{xrefautomaticsectiontitle} flag is on, so
@samp{@@xref@{Topic@}} would produce output like ``See `All about the
Topic@w{'}''.



@node Cross References
@nodedescription Writing cross-references.
@chapter Cross-references
@cindex Making cross-references
@cindex Cross-references
@cindex References

@dfn{Cross-references} are used to refer the reader to other parts of the
same or different Texinfo files.

Use cross-references to provide access to information that is too
detailed for the current context, or incidental to it.  An online
help system or a reference manual is not like a novel; few read such
documents in sequence from beginning to end.  Instead, people look
up what they need.  For this reason, such creations should contain
many cross-references to help readers find other information that
they may not have read.

In a printed manual, a cross-reference results in a page reference,
unless it is to another manual altogether, in which case the
cross-reference names that manual.  In Info, a cross-reference results
in an entry that you can follow using the Info @samp{f} command.
(@xref{Help-Xref,, Following cross-references, info, Info}.)  In HTML, a
cross-reference results in an hyperlink.  In DocBook, the @code{<link>}
element is used for cross-references unless it is to another manual,
in which case the cross-reference names that manual.

The various cross-reference commands use nodes, anchors
(@pxref{@code{@@anchor}}) or float labels (@pxref{@code{@@float}}) to define
cross-reference locations.  When @TeX{} generates a DVI file, it records each
cross-reference location page number and uses the page numbers in making
references.  Thus, even if you are writing a manual that will only be printed,
and not used online, you must nonetheless write @code{@@node} lines (or
@code{@@anchor} anchors) in order to name the places to which you make
cross-references.




@node Cross Reference Commands
@nodedescription A summary of the different commands.
@section Different Cross-reference Commands
@cindex Different cross-reference commands

There are three different cross-reference commands:

@table @code
@item @@xref
Used to start a sentence with an Info cross-reference saying
@samp{*Note @var{name}: @var{node}.} or with @w{`See @dots{}'}
in other output formats.

@item @@ref
Used within or, more often, at the end of a sentence; produces
an Info cross-reference saying @samp{*note @var{name}: @var{node}.},
and just the reference in other output formats,
without the preceding `See'.

@item @@pxref
Used within parentheses, at the end of a sentence, or otherwise before
punctuation, to make a reference.  Its output starts with a lowercase
@samp{*note} in Info, and with a lowercase `see' in the other output
formats.  (@samp{p} is for `parenthesis'.)
@end table

Additionally, there are commands to produce references to documents
outside the Texinfo system.  The @code{@@cite} command is used
to make references to books and manuals.  @code{@@url} produces
a @acronym{URL}, for example a reference to a page on the World
Wide Web.


@node Cross Reference Parts
@nodedescription A cross-reference has several parts.
@section Parts of a Cross-reference
@cindex Cross-reference parts
@cindex Parts of a cross-reference
@anchor{Reference Syntax} @c merged node

A cross-reference command requires only one argument, which is
the name of the node to which it refers.  A cross-reference command
may contain up to four additional arguments.
The template for a full five argument cross-reference looks like
this:

@example
@group
@@xref@{@var{node-name}, @var{online-label}, @var{printed-label},
@var{manual-name}, @var{printed-manual-title}@}
@end group
@end example

The five possible arguments for a cross-reference are:

@enumerate
@item
The node or anchor name.  This is the location to which the cross-reference
takes you.  In a printed document, the location of the node provides the
page reference only for references within the same document.
Use @code{@@node} to define the node (@pxref{Writing a Node}),
@code{@@anchor} (@pxref{@code{@@anchor}}), or @code{@@float}
(@pxref{@code{@@float}}) with a label.
This argument is required (except for reference to whole manuals).

Write a node name in a cross-reference in exactly the same way as in
the @code{@@node} line, including the same capitalization; otherwise, the
processors may not find the reference.

@item
A label for online output.  It is usually omitted; then
the topic description (third argument) is used if it was specified;
if that was omitted as well, the node name is used.

@item
A label for printed output.  Often, this is the title or topic of the
section.  This is used as the name of the reference in the printed
manual.  If omitted, the node name is used.

@item
The name of the manual to which the reference refers, if it is
outside the current manual, in a different Texinfo file.

@item
The title of the printed manual to which the reference refers,
from a different Texinfo file.
@end enumerate

Whitespace before and after the commas separating these arguments is
ignored.  To include a comma in one of the arguments, use
@code{@@comma@{@}} (@pxref{Inserting a Comma}).

Cross-references with one, two, three, four, and five arguments are
described separately in following sections.

@cindex Comma after cross-reference
When processing with TeX, a comma is automatically inserted after the
page number for cross-references to within the same manual, unless the
closing brace of the argument is followed by non-whitespace (such as a
comma or period).  This gives you the choice of whether to have a comma
there in other output formats.  For example,

@example
@@xref@{Another Section@} for more info
@end example

@noindent
with TeX produces @w{`See Another Section, page @var{ppp}, for more info'},
and in the Info output produces
@w{@samp{*Note Another Section:: for more info}}.


If an unwanted comma is added, follow the argument
with a command such as @samp{@@:}.  For example,
@w{@samp{@@xref@{Hurricanes@}@@: --- for the details}} produces

@quotation
See Hurricanes, page @var{ppp} --- for the details
@end quotation

@noindent instead of
@w{`See Hurricanes, page @var{ppp}, --- for the details'}.

@command{texi2any} warns and protect names when the text of a cross-reference
(and node names and menu items) contains a problematic construct that could
interfere with its parsing in Info.  @xref{Info Node Names Constraints}.


@raisesections
@node One Argument
@nodedescription @code{@@xref} with one argument.
@subsection @code{@@xref} with One Argument
@cindex One-argument form of cross-references

The simplest form of @code{@@xref} takes one argument, the name of
another node in the same Texinfo file.

@need 700
@noindent
For example,

@example
@@xref@{Tropical Storms@}.
@end example

@noindent
produces

@example
*Note Tropical Storms::.
@end example

@noindent
in Info and

@quotation
See Section 3.1 [Tropical Storms], page 24.
@end quotation

@noindent
in a printed manual.


@node Two Arguments
@nodedescription @code{@@xref} with two arguments.
@subsection @code{@@xref} with Two Arguments
@cindex Two-argument form of cross-references

With two arguments, the second is used as a label for the online output.

@need 750
@noindent
The template is like this:

@example
@@xref@{@var{node-name}, @var{online-label}@}.
@end example

@need 700
@noindent
For example,

@example
@@xref@{Electrical Effects, Lightning@}.
@end example

@noindent
produces:

@example
*Note Lightning: Electrical Effects.
@end example

@noindent
in Info and

@quotation
See Section 5.2 [Electrical Effects], page 57.
@end quotation

@noindent
in a printed manual, where the node name is printed.

The second argument to cross-references shares constraints
with node names.  The potentially problematic character in this
context is the colon.  @xref{Info Node Names Constraints}.


@node Three Arguments
@nodedescription @code{@@xref} with three arguments.
@subsection @code{@@xref} with Three Arguments
@cindex Three-argument form of cross-references

A third argument replaces the node name in the printed output.  The third
argument should be the name of the section in the printed output, or
else state the topic discussed by that section.

@need 750
@noindent
The template is like this:

@example
@group
@@xref@{@var{node-name}, @var{online-label}, @var{printed-label}@}.
@end group
@end example

@need 700
@noindent
For example,

@example
@group
@@xref@{Electrical Effects, Lightning, Thunder and Lightning@},
for details.
@end group
@end example

@noindent
produces

@example
*Note Lightning: Electrical Effects, for details.
@end example

@noindent
in Info and

@quotation
See Section 5.2 [Thunder and Lightning], page 57, for details.
@end quotation

@noindent
in a printed manual.

If a third argument is given and the second one is empty, then the
third argument serves for both.  (Note how two commas, side by side, mark
the empty second argument.)

@example
@group
@@xref@{Electrical Effects, , Thunder and Lightning@},
for details.
@end group
@end example

@noindent
produces

@example
*Note Thunder and Lightning: Electrical Effects, for details.
@end example

@noindent
in Info and

@quotation
See Section 5.2 [Thunder and Lightning], page 57, for details.
@end quotation

@noindent
in a printed manual.

The third argument to cross-references shares constraints
with node names.  The potentially problematic character in this
context is the colon.  @xref{Info Node Names Constraints}.

As a practical matter, it is often best to write cross-references with
just the first argument if the node name and the section title are the
same (or nearly so), and with the first and third arguments only if the
node name and title are different.

@findex xrefautomaticsectiontitle
@anchor{@code{xrefautomaticsectiontitle}}
Texinfo offers a setting to use the section title instead of node
names by default in cross-references (an explicitly specified third
argument still takes precedence):

@example
@@xrefautomaticsectiontitle on
@end example

This setting is also used for cross-references to anchors defined with
@code{@@namedanchor} (@pxref{@code{@@anchor}}).

Typically this line would be given near the beginning of the document
and used for the whole manual.  But you can turn it off if you want
(@code{@@xrefautomaticsectiontitle off}), for example, if you're
including some other sub-document that doesn't have suitable section
names.  This setting also applies to node headers in HTML: if
@code{@@xrefautomaticsectiontitle} is on, the sections names are used
in node headers instead of the node names when possible.  This setting has
no effect in Info or plain text output.


@node Four and Five Arguments
@nodedescription @code{@@xref} with four and five arguments.
@subsection @code{@@xref} with Four and Five Arguments
@cindex Four- and five argument forms of cross-references

In a cross-reference, a fourth argument specifies the name of another
manual, different from the file in which the reference appears, and
a fifth argument specifies its title as a printed manual.

@need 800
@noindent
The full template is:

@example
@group
@@xref@{@var{node-name}, @var{online-label}, @var{printed-label},
@var{manual-name}, @var{printed-manual-title}@}.
@end group
@end example

@need 700
@noindent
For example,

@example
@@xref@{Electrical Effects, Lightning, Thunder and Lightning,
weather, An Introduction to Meteorology@}.
@end example

@noindent
produces this output in Info:

@example
*Note Lightning: (weather)Electrical Effects.
@end example

@noindent
As you can see, the name of the manual is enclosed in parentheses
and precedes the name of the node.  In HTML, the manual name and
the node name are used to construct the hyperlink URL
(@pxref{HTML Xref}), while the link text is based on the label.

@noindent
In a printed manual, the reference looks like this:

@quotation
See section ``Thunder and Lightning'' in @cite{An Introduction to
Meteorology}.
@end quotation

@noindent
The title of the printed manual is typeset like @code{@@cite}; and the
reference lacks a page number since the page a reference refers when
that reference is to another manual cannot be known.

Next case: often, you will leave out the second argument when you use
the long version of @code{@@xref}.  In this case, the third argument,
the topic description, will be used as the cross-reference name in
online formats.  For example,

@example
@@xref@{Electrical Effects, , Thunder and Lightning,
weather, An Introduction to Meteorology@}.
@end example

@noindent
produces

@example
@group
*Note Thunder and Lightning: (weather)Electrical Effects.
@end group
@end example

@noindent
in Info and

@quotation
See section ``Thunder and Lightning'' in @cite{An Introduction to
Meteorology}.
@end quotation

@noindent
in a printed manual.

Next case: If the node name and the section title are the same in the
other manual, you may also leave out the section title.  In this case,
the node name is used in both instances.  For example,

@example
@@xref@{Electrical Effects,,,
weather, An Introduction to Meteorology@}.
@end example

@noindent
produces

@example
@group
*Note (weather)Electrical Effects::.
@end group
@end example

@noindent
in Info and

@quotation
See section ``Electrical Effects'' in @cite{An Introduction to
Meteorology}.
@end quotation

@noindent
in a printed manual.

In general, there is no reason to have a manual name argument without a
printed manual argument, unless no printed manual is generated.
You may also want to refer to another manual file that
is within a single printed manual---when multiple Texinfo files are
incorporated into the same printed manual but can create separate output files
in other output formats.  In this case, you need to specify only the fourth
argument, and not the fifth.  If the printed manual title argument is missing, the
manual name will be used instead in printed output.

A printed manual title argument without an online manual argument is of
little use unless only a printed manual is generated from the Texinfo source.
The result in online formats depends on the format, and
can be, for example, an empty manual name or a reference to the printed
manual formatted in a similar way to the printed output.

Finally, it's also allowed to leave out all the arguments
@emph{except} the fourth and fifth, to refer to another manual as a
whole.  See the next section.

@lowersections


@node Referring to a Manual as a Whole
@nodedescription Refer to an entire manual.
@section Referring to a Manual as a Whole
@cindex Manual, referring to as a whole
@cindex Referring to an entire manual
@anchor{Top Node Naming} @c old name

Ordinarily, you must always name a node in a cross-reference.
However, it's not unusual to want to refer to another manual as a
whole, rather than a particular section within it.  In this case,
giving any section name is an unnecessary distraction.

So, with cross-references to other manuals (@pxref{Four and Five
Arguments}), if the first argument is either @samp{Top} (capitalized
just that way) or omitted entirely, and the third argument is omitted,
the printed output includes no node or section name.  (The Info output
includes @samp{Top} if it was given.)  For example,

@example
@@xref@{Top,,, make, The GNU Make Manual@}.
@end example

@noindent produces

@example
@group
*Note (make)Top::.
@end group
@end example

@noindent and

@quotation
See @cite{The GNU Make Manual}.
@end quotation

@noindent
Info readers will go to the Top node of the manual whether
or not the `Top' node is explicitly specified.

It's also possible (and is historical practice) to refer to a whole
manual by specifying the `Top' node and an appropriate entry for the
third argument to the @code{@@xref} command.  Using this idiom, to
make a cross-reference to @cite{The GNU Make Manual}, you would write:

@example
@@xref@{Top,, Overview, make, The GNU Make Manual@}.
@end example

@noindent
which produces

@example
*Note Overview: (make)Top.
@end example

@noindent
in Info and

@quotation
See section ``Overview'' in @cite{The GNU Make Manual}.
@end quotation

@noindent
in a printed manual.

In this example, @samp{Top} is the name of the first node, and
@samp{Overview} is the name of the first section of the manual.  There
is no widely-used convention for naming the first section in a printed
manual, this is just what the Make manual happens to use.  This
arbitrariness of the first name is a principal reason why omitting the
third argument in whole-manual cross-references is preferable.


@node @code{@@xref}
@nodedescription Begin a reference with `See' @dots{}
@section @code{@@xref}

@anchor{xref}@c old name
@findex xref
@cindex Cross-references using @code{@@xref}
@cindex References using @code{@@xref}

The @code{@@xref} command generates a cross-reference for the
beginning of a sentence.  Examples of using @code{@@xref} are
in previous sections.


@node @code{@@ref}
@nodedescription A reference for the last part of a sentence.
@section @code{@@ref}

@anchor{ref}@c old name
@findex ref
@cindex Cross-references using @code{@@ref}
@cindex References using @code{@@ref}

@code{@@ref} is nearly the same as @code{@@xref} except that it does
not generate a `See' in the output, just the reference itself.
This makes it useful as the last part of a sentence.

@noindent For example,

@cindex Hurricanes
@example
For more information, @@pxref@{This@}, and @@ref@{That@}.
@end example

@noindent
produces in Info:

@example
For more information, *note This::, and *note That::.
@end example

@noindent
and in printed output:

@quotation
For more information, see Section 1.1 [This], page 1,
and Section 1.2 [That], page 2.
@end quotation

The @code{@@ref} command can tempt writers to express themselves in a
manner that is suitable for a printed manual but looks awkward in the
Info format.  Bear in mind that your audience could be using both the
printed and other output formats such as Info.  For example:

@cindex Sea surges
@example
Sea surges are described in @@ref@{Hurricanes@}.
@end example

@noindent
looks ok in the printed output:

@quotation
Sea surges are described in Section 6.7 [Hurricanes], page 72.
@end quotation

@noindent
but is awkward to read in Info, ``note'' being a verb:

@example
Sea surges are described in *note Hurricanes::.
@end example


@node @code{@@pxref}
@nodedescription How to write a parenthetical cross-reference.
@section @code{@@pxref}

@anchor{pxref}@c old name
@findex pxref
@cindex Cross-references using @code{@@pxref}
@cindex References using @code{@@pxref}

The parenthetical reference command, @code{@@pxref}, is nearly the
same as @code{@@xref}, but it is best used within parentheses.
The command differs from @code{@@xref} in that the reference is
typeset with a lowercase `see' rather than an uppercase `See'.
In Info, @samp{*note} is output.

@noindent
With one argument, a parenthetical cross-reference looks like this:

@cindex Flooding
@example
@dots{} storms cause flooding (@@pxref@{Hurricanes@}) @dots{}
@end example

@need 800
@noindent
which produces

@example
@group
@dots{} storms cause flooding (*note Hurricanes::) @dots{}
@end group
@end example

@noindent
in Info and

@quotation
@dots{} storms cause flooding (see Section 6.7 [Hurricanes], page 72) @dots{}
@end quotation

@noindent
in a printed manual.

The effect of @samp{@@pxref@{@var{node-name}@}} is identical to that of
@samp{@@ref@{@var{node-name}@}} in Info output.  Hence, it may be
preferable, when not inside parentheses, to write
@samp{see @@ref@{@var{node-name}@}} rather
than @samp{@@pxref@{@var{node-name}@}} when you want the word ``see''
to occur in the output, as Info readers cannot reliably insert this
word based on the @samp{*note} cross-reference marker (for example,
using the @code{Info-hide-note-references} variable; see
@ref{Help-Inv, Help-Inv, Invisible text in Emacs Info, info, Info: An
Introduction}).

In past versions of Texinfo, it was not allowed to write punctuation
after a @code{@@pxref}, so it could be used @emph{only} before a
right parenthesis.  This is no longer the case.


@node @code{@@anchor}
@nodedescription Defining arbitrary cross-reference targets
@section @code{@@anchor}: Defining Arbitrary Cross-reference Targets

@anchor{anchor}@c old name
@findex anchor
@cindex Anchors
@cindex Cross-reference targets, arbitrary
@cindex Targets for cross-references, arbitrary

You may wish to create cross-references to arbitrary positions
in a document, not just to the beginning of nodes.  The @code{@@anchor}
command marks such a position in your document, called an @dfn{anchor}.
Put an @code{@@anchor} command just before the position you wish to
refer to.  For example:

@example
This marks the @@anchor@{x-spot@}spot.
@dots{}
@@xref@{x-spot,,the spot@}.
@end example

@noindent This produces:

@example
This marks the spot.
@dots{}
See [the spot], page 1.
@end example

The brace-delimited argument to @code{@@anchor}, here @samp{x-spot},
is the @dfn{anchor name}, which plays the same role as a node name.
The anchor name is used to create cross-references to the anchor, as
with an @code{@@xref} or other cross-reference command, as shown
(@pxref{Cross References}).  As you can see, the @code{@@anchor} command
itself produces no output.

Anchor names share the same constraints as nodes on the characters
that can be included (@pxref{Info Node Names Constraints}).
Anchor names, node names and float labels may not conflict.

You can put the @code{@@anchor} command on a line by itself if that
helps readability of the source.  Whitespace (including newlines) is
ignored after @code{@@anchor}.

@ignore
Anchors, nodes and float labels are
given similar treatment in some ways; for example, the
@code{goto-node} command takes either an anchor name or a node name as
an argument.  (@xref{Go to node,,, info, Info}.).  Anchor names and float
labels could also appear in menus (@pxref{Menus}) and node direction
pointers (@pxref{Writing a Node}), although this is not recommended.
@end ignore

@cindex Nodes, deleting or renaming
When you delete or rename a node, it is usually a good idea to define an
@code{@@anchor} with the old name.  That way, any links to the old node,
whether from other Texinfo manuals or general web pages, keep working.
Place any such anchors at the start of the node, after the @samp{@@node}
line and any structuring or heading command line.

By default, links to anchors are unaffected by the
@code{xrefautomaticsectiontitle} setting (see @ref{Three Arguments,,
@code{xrefautomaticsectiontitle}}).  This means that the anchor name
will be used as label text in the cross-reference.

@findex namedanchor
However, you can define a @dfn{named anchor} using @code{@@namedanchor}.
The template is:

@example
@@namedanchor@{@var{anchor-name}, @var{xref-name}@}
@end example

Use this exactly as you would @code{@@anchor}, except the additional
@var{xref-name} parameter gives the text to use if
@code{xrefautomaticsectiontitle} is on.  For example:

@example
This marks the @@namedanchor@{x-spot, the spot@}spot.
@dots{}
@@set xrefautomaticsectiontitle on
@@xref@{x-spot@}.
@end example

@noindent This produces:

@example
This marks the spot.
@dots{}
See [the spot], page 1.
@end example

@node @code{@@link}
@nodedescription How to make a plain link.
@section @code{@@link}: Plain, unadorned hyperlink
@findex link
@cindex Cross-references using @code{@@link}
@cindex Plain link
@cindex Plain hyperlink

@code{@@link} produces a plain hyperlink in output formats that
support it, including in HTML, DocBook, @LaTeX{} and online PDF@.
The template is:

@example
@@link@{@var{node-name}, @var{label}, @var{manual-name}@}
@end example

@var{node-name} is the name of the target node or anchor.
Either or both of @var{label} and @var{manual-name} can
be omitted.  @var{label}, if given, is the text to use for the
link.  @var{manual-name} is the name of the external manual that the
target appears within; if not given, the reference is to the current
manual.

@code{@@link} has similar output to @code{@@ref}, except that it does
not produce any extra text around the link label in Info or printed output
that would mark it as a cross-reference.

Be careful about using @code{@@link} to produce links that are
necessary for a user to move around a manual, as these links will do
nothing in some output formats.  @code{@@link} is best used to add
convenience links that are nonetheless not essential for a reader
to understand the text of the manual.  For example, you might use
@code{@@link} in a code sample to reference documentation of a symbol
in a programming library.



@node @code{@@inforef}
@nodedescription How to refer to an Info-only file.
@section @code{@@inforef}: Cross-references to Info-only Material

@anchor{inforef}@c old name
@findex inforef
@cindex Cross-references using @code{@@inforef}
@cindex References using @code{@@inforef}

@code{@@inforef} is used for making cross-references to Info
documents---even from a printed manual.  This was originally
used for Info files that were not generated from any Texinfo source.
The command is now obsolete and should not be used.  In addition
to having little use, similar output can be obtained with
@code{@@xref}, @code{@@ref} or @code{@@pxref} with the Info
file name as the fourth argument and no fifth argument.

The command takes either two or three arguments, in the following
order:

@enumerate
@item
The node name.

@item
The cross-reference name (optional).

@item
The Info file name.
@end enumerate

@noindent
The template is:

@example
@@inforef@{@var{node-name}, @var{cross-reference-name}, @var{info-file-name}@}
@end example


@node @code{@@url}
@nodedescription How to refer to a uniform resource locator.
@section @code{@@url}, @code{@@uref@{@var{url}[, @var{text}][, @var{replacement}]@}}

@anchor{uref}@c old name
@anchor{url}
@cindex URL @subentry referring to

@findex url
@cindex @code{href}, producing HTML
@code{@@url} produces a reference to a uniform resource locator
(URL@:).  It takes one mandatory argument, the URL@:, and two optional
arguments which control the text that is displayed.  In HTML and PDF
output, @code{@@url} produces a link you can follow.  (To merely
indicate a URL without creating a link people can follow, use
@code{@@indicateurl}, @pxref{@code{@@indicateurl}}.)

@findex uref
@code{@@uref} is a synonym for @code{@@url}.
(Originally, @code{@@url} had the meaning of @code{@@indicateurl}
and @code{@@uref} was required to produce a working link, but
in practice @code{@@url} was almost always misused.  So we've changed 
the meaning.)

The second argument, if specified, is the text to display (the default
is the URL itself); in output formats other than HTML, the URL is
output in addition to this text.

@cindex Man page, reference to
The third argument, if specified, is the text to display, but in this
case the URL is not output in any format.  This is useful when the
text is already sufficiently referential, as in a man page.  Also, if
the third argument is given, the second argument is ignored.


@node @code{@@url} Examples
@nodedescription Examples of using all the forms of @code{@@url}.
@subsection @code{@@url} Examples

@cindex @code{@@url}, examples of using
@cindex URL @subentry examples of displaying

First, here is an example of the simplest form of @code{@@url}, with
just one argument.  The given URL is both the target and the visible
text of the link:

@example
The official GNU ftp site is @@url@{https://ftp.gnu.org/gnu@}.
@end example

@noindent produces:
@display
The official GNU ftp site is @url{https://ftp.gnu.org/gnu}.
@end display

@subsubheading Two-argument form of @code{@@url}

Here is an example of the two-argument form:
@example
The official @@url@{https://ftp.gnu.org/gnu, GNU ftp site@}
holds programs and texts.
@end example

@noindent which produces:
@display
The official @url{https://ftp.gnu.org/gnu, GNU ftp site}
holds programs and texts.
@end display

@noindent The HTML output is this:
@example
The official <a href="https://ftp.gnu.org/gnu">GNU ftp site</a>
holds programs and texts.
@end example

@noindent In other formats, the output is like this:
@example
The official GNU ftp site (https://ftp.gnu.org/gnu)
holds programs and texts.
@end example

@subsubheading Three-argument form of @code{@@url}

Finally, an example of the three-argument form:
@example
The @@url@{/man.cgi/1/ls,,ls@} program @dots{}
@end example

@noindent which, except for HTML, produces:
@display
The @url{/man.cgi/1/ls,,ls} program @dots{}
@end display

@noindent but with HTML:
@example
The <a href="/man.cgi/1/ls">ls</a> program @dots{}
@end example


By the way, some people prefer to display URLs in the unambiguous
format:

@display
<URL:http://@var{host}/@var{path}>
@end display

@noindent
@cindex @code{<URL...>} convention, not used
You can use this form in the input file if you wish.  We feel it's not
necessary to include the @samp{<URL:} and @samp{>} in the output,
since to be useful any software that tries to detect URLs in text
already has to detect them without the @samp{<URL:}.


@node URL Line Breaking
@nodedescription How lines are broken within @code{@@url} text.
@subsection URL Line Breaking

@cindex Line breaks @subentry URLs
@cindex Breakpoints within URLs
@TeX{} allows line breaking within URLs at only a few characters
(which are special in URLs): @samp{&}, @samp{.}, @samp{#}, @samp{?},
and @samp{/} (but not between two @samp{/} characters).  A tiny amount
of stretchable space is also inserted around these characters to help
with line breaking.

For HTML output, modern browsers will also do line breaking within
displayed URLs.  If you need to allow breaks at other characters you
can insert @code{@@/} as needed (@pxref{Line Breaks}).

@findex urefbreakstyle
By default, in @TeX{} any such breaks at special characters will occur
after the character.  Some people prefer such breaks to happen before
the special character.  This can be controlled with the
@code{@@urefbreakstyle} command (this command has effect only in
@TeX{}):

@example
@@urefbreakstyle @var{how}
@end example

@noindent where the argument @var{how} is one of these words:

@vindex after@r{, value for @code{@@urefbreakstyle}}
@vindex before@r{, value for @code{@@urefbreakstyle}}
@vindex none@r{, value for @code{@@urefbreakstyle}}
@table @samp
@item after
(the default) Potentially break after the special characters.
@item before
Potentially break before the special characters.
@item none
Do not consider breaking at the special characters at all; any potential
breaks must be manually inserted.
@end table


@node @code{@@url} PDF Output Format
@nodedescription A special option to hide links in PDF output.
@subsection @code{@@url} PDF Output Format

@cindex PDF output of URLs
@cindex URLs, PDF output of

If the ultimate purpose of a PDF is only to be viewed online, perhaps
similar to HTML in some inchoate way, you may not want the URLs to be
included in the visible text (just as URLs are not visible to readers
of web pages).  Texinfo provides a PDF-specific option for this, which
must be used inside @code{@@tex}:

@findex \urefurlonlylinktrue
@example
@@tex
\global\urefurlonlylinktrue
@@end tex
@end example

The result is that @code{@@url@{https://www.gnu.org, GNU@}} has the
visible output of just `GNU', with a link target of
@url{https://www.gnu.org}.  Ordinarily, the visible output would
include both the label and the url: `GNU (@url{https://www.gnu.org})'.

This option only has effect when the PDF output is produced with the
pdf@TeX{} program, not with other ways of getting from Texinfo to PDF
(e.g., @TeX{} to DVI to PDF)@.  Consequently, it is ok to specify this
option unconditionally within @code{@@tex}, as shown above.  It is
ignored when DVI is being produced.


@node @code{@@cite}
@nodedescription How to refer to books not in the Info system.
@section @code{@@cite}@{@var{reference}@}

@anchor{cite}@c old name
@findex cite

Use the @code{@@cite} command for the name of a book that lacks a
companion Info file.  For example, we could refer to @cite{A Book}.
The command selects a slanted font in the printed
manual, and generates quotation marks in the Info file.

If a book is written in Texinfo, it is better to use a cross-reference
command since a reader can easily follow such a reference in Info.
@xref{@code{@@xref}}.

@node PDF Colors
@nodedescription Colorizing URLs and other links in PDF output.
@section PDF Colors

@cindex Colored links, in PDF output
@cindex Links, coloring in PDF output
@cindex URLs, coloring in PDF output

By default, URLs and cross-reference links are printed in black in PDF
output.  Very occasionally, however, you may want to highlight such
``live'' links with a different color, as is commonly done on web
pages.  Texinfo provides a PDF-specific option for specifying these
colors, which must be used inside @code{@@tex}:

@findex \linkcolor
@findex \urlcolor
@example
@@tex
\global\def\linkcolor@{1 0 0@}  % red
\global\def\urlcolor@{0 1 0@}   % green
@@end tex
@end example

@code{\urlcolor} changes the color of @code{@@url} output (both the
actual URL and any textual label), while @code{\linkcolor} changes the
color for cross-references to nodes, etc.  They are independent.

@cindex RGB color specification.
The three given values must be numbers between 0 and 1, specifying the
amount of red, green, and blue respectively.

These definitions only have an effect when the PDF output is produced
with the pdf@TeX{} program, not with other ways of getting from
Texinfo to PDF (e.g., @TeX{} to DVI to PDF)@.  Consequently, it is ok
to specify this option unconditionally within @code{@@tex}, as shown
above.  It is ignored when DVI is being produced.

We do not recommend colorizing just for fun; unless you have a
specific reason to use colors, best to skip it.




@node Marking Text
@nodedescriptionblock
Marking words and phrases as code, keyboard input, meta-syntactic
variables, and the like.
@end nodedescriptionblock
@chapter Marking Text, Words and Phrases
@cindex Paragraph, marking text within
@cindex Marking words and phrases
@cindex Words and phrases, marking them
@cindex Marking text within a paragraph
@cindex Text, marking up

In Texinfo, you can mark words and phrases in a variety of ways.
The Texinfo processors use this information to determine how to
highlight the text.
You can specify, for example, whether a word or phrase is a
defining occurrence, a metasyntactic variable, or a symbol used in a
program.  Also, you can emphasize text, in several different ways.


@node Indicating
@nodedescription How to indicate definitions, files, etc.
@section Indicating Definitions, Commands, etc.

@cindex Highlighting text
@cindex Indicating commands, definitions, etc.

Texinfo has commands for indicating just what kind of object a piece
of text refers to.  For example, email addresses are marked by
@code{@@email}; that way, the result can be a live link to send email
when the output format supports it.  If the email address was simply
marked as ``print in a typewriter font'', that would not be possible.


@node Useful Highlighting
@nodedescription Highlighting provides useful information.
@subsection Highlighting Commands are Useful

The commands serve a variety of purposes:

@table @code
@item @@code@{@var{sample-code}@}
Indicate text that is a literal example of a piece of a program.
@xref{@code{@@code}}.

@item @@kbd@{@var{keyboard-characters}@}
Indicate keyboard input.  @xref{@code{@@kbd}}.

@item @@key@{@var{key-name}@}
Indicate the conventional name for a key on a keyboard.
@xref{@code{@@key}}.

@item @@samp@{@var{text}@}
Indicate text that is a literal example of a sequence of characters.
@xref{@code{@@samp}}.

@item @@verb@{@var{text}@}
Write a verbatim sequence of characters.
@xref{@code{@@verb}}.

@item @@var@{@var{metasyntactic-variable}@}
Indicate a metasyntactic variable.  @xref{@code{@@var}}.

@item @@env@{@var{environment-variable}@}
Indicate an environment variable.  @xref{@code{@@env}}.

@item @@file@{@var{file-name}@}
Indicate the name of a file.  @xref{@code{@@file}}.

@item @@command@{@var{command-name}@}
Indicate the name of a command.
@xref{@code{@@command}}.

@item @@option@{@var{option}@}
Indicate a command-line option.
@xref{@code{@@option}}.

@item @@dfn@{@var{term}@}
Indicate the introductory or defining use of a term.
@xref{@code{@@dfn}}.

@item @@cite@{@var{reference}@}
Indicate the name of a book.  @xref{@code{@@cite}}.

@item @@abbr@{@var{abbreviation}@}
Indicate an abbreviation, such as `Comput.'.

@item @@acronym@{@var{acronym}@}
Indicate an acronym.  @xref{@code{@@acronym}}.

@item @@indicateurl@{@var{uniform-resource-locator}@}
Indicate an example (that is, nonfunctional) uniform resource locator.
@xref{@code{@@indicateurl}}.  (Use @code{@@url} (@pxref{@code{@@url}}) for
live URLs.)

@item @@email@{@var{email-address}[, @var{displayed-text}]@}
Indicate an electronic mail address.  @xref{@code{@@email}}.

@end table


@node @code{@@code}
@nodedescription Indicating program code.
@subsection @code{@@code}@{@var{sample-code}@}

@anchor{code}@c old name
@findex code

@cindex Syntactic tokens, indicating
Use the @code{@@code} command to indicate text that is a piece of a
program and which consists of entire syntactic tokens.  Enclose the
text in braces.

@cindex Expressions in a program, indicating
@cindex Keywords, indicating
@cindex Reserved words, indicating
Thus, you should use @code{@@code} for an expression in a program, for
the name of a variable or function used in a program, or for a
keyword in a programming language.

Use @code{@@code} for command names in languages that resemble
programming languages, such as Texinfo.  For example, @code{@@code} and
@code{@@samp} are produced by writing @samp{@@code@{@@@@code@}} and
@samp{@@code@{@@@@samp@}} in the Texinfo source, respectively.

@cindex Case, not altering in @code{@@code}
It is incorrect to alter the case of a word inside a @code{@@code}
command when it appears at the beginning of a sentence.  Most computer
languages are case sensitive.  In C, for example, @code{Printf} is
different from the identifier @code{printf}, and most likely is a
misspelling of it.  Even in languages which are not case sensitive, it
is confusing to a human reader to see identifiers spelled in different
ways.  Pick one spelling and always use that.  If you do not want to
start a sentence with a command name written all in lowercase, you
should rearrange the sentence.

The @code{@@code} argument is typeset in a typewriter (monospace) font.
where the output format allows this.  For example,

@example
The function returns @@code@{nil@}.
@end example

@noindent
produces this:

@quotation
The function returns @code{nil}.
@end quotation

Here are some cases for which it is preferable @emph{not} to use @code{@@code}:

@itemize @bullet
@item
For shell command names, such as @command{ls} (use @code{@@command}).

@item
For environment variables, such as @env{TEXINPUTS} (use @code{@@env}).

@item
For shell options, such as @samp{-c}, when such options stand alone (use
@code{@@option}).

@item
An entire shell command often looks better if written using
@code{@@samp} rather than @code{@@code}.  In this case, the rule is to
choose the more pleasing format.

@item
For a string of characters shorter than a syntactic token.  For example,
if you are writing about @samp{goto-ch}, which is just a part of the
name for the @code{goto-char} Emacs Lisp function, you should use
@code{@@samp}.

@item
In general, when writing about the characters used in a token; for
example, do not use @code{@@code} when you are explaining what letters
or printable symbols can be used in the names of functions.  (Use
@code{@@samp}.)  Also, you should not use @code{@@code} to mark text
that is considered input to programs unless the input is written in a
language that is like a programming language.  For example, you should
not use @code{@@code} for the keystroke commands of GNU Emacs (use
@code{@@kbd} instead) although you may use @code{@@code} for the names
of the Emacs Lisp functions that the keystroke commands invoke.

@end itemize

By default, @TeX{} will consider breaking lines at @samp{-} and
@samp{_} characters within @code{@@code} and related commands.  This
can be controlled with @code{@@allowcodebreaks}
(@pxref{@code{@@allowcodebreaks}}).  In the HTML output breaking
lines is up to the browser's behavior.  For Info, it seems better
never to make such breaks.

For Info and plaintext, quotation characters are usually output around
the output of the @code{@@code} command and related commands
(e.g., @code{@@kbd}, @code{@@command}) except
in typewriter-like contexts such as the @code{@@example} environment
(@pxref{@code{@@example}}) and @code{@@code} itself, etc.
To control which quoting characters are inserted by
@command{texi2any} in the output of @samp{@@code}, etc., see the
@code{OPEN_QUOTE_SYMBOL} and @code{CLOSE_QUOTE_SYMBOL} customization
variables (@pxref{Customization Variables for Multiple Formats}).


@node @code{@@kbd}
@nodedescription Showing keyboard input.
@subsection @code{@@kbd}@{@var{keyboard-characters}@}

@anchor{kbd}@c old name
@findex kbd
@cindex Keyboard input

Use the @code{@@kbd} command for characters of input to be typed by
users.  For example, to refer to the characters @kbd{M-a}, write:

@example
@@kbd@{M-a@}
@end example

@noindent
and to refer to the characters @kbd{M-x shell}, write:

@example
@@kbd@{M-x shell@}
@end example

@cindex User input
@cindex Slanted typewriter font, for @code{@@kbd}
By default, the @code{@@kbd} command produces a different font (slanted
typewriter instead of normal typewriter, where the output format allows),
so users can distinguish the characters that they are supposed
to type from those that the computer outputs.

@findex kbdinputstyle
Since the usage of @code{@@kbd} varies from manual to manual, you can
control the font switching with the @code{@@kbdinputstyle} command.
This command has no effect on Info output.  Write this command at the
beginning of a line with a single word as an argument, one of the
following:

@vindex distinct@r{, value for @code{@@kbdinputstyle}}
@vindex example@r{, value for @code{@@kbdinputstyle}}
@vindex code@r{, value for @code{@@kbdinputstyle}}
@table @samp
@item code
Always use the same font for @code{@@kbd} as @code{@@code}.
@item example
Use the distinguishing font for @code{@@kbd} only in @code{@@example}
and similar environments.
@item distinct
(the default) Always use the distinguishing font for @code{@@kbd}.
@end table

You can embed another @@-command inside the braces of a @code{@@kbd}
command.  Here, for example, is the way to describe a command that
would be described more verbosely as ``press the @samp{r} key and then
press the @key{RETURN} key'':

@example
@@kbd@{r @@key@{RET@}@}
@end example

@noindent
This produces: @kbd{r @key{RET}}.  (The present manual uses the
default for @code{@@kbdinputstyle}.)

You also use the @code{@@kbd} command if you are spelling out the letters
you type; for example:

@example
To give the @@code@{logout@} command,
type the characters @@kbd@{l o g o u t @@key@{RET@}@}.
@end example

@noindent
This produces:

@quotation
To give the @code{logout} command,
type the characters @kbd{l o g o u t @key{RET}}.
@end quotation

(Also, this example shows that you can add spaces for clarity.  If you
explicitly want to mention a space character as one of the characters of
input, write @kbd{@@key@{SPC@}} for it.)


@node @code{@@key}
@nodedescription Specifying keys.
@subsection @code{@@key}@{@var{key-name}@}

@anchor{key}@c old name
@findex key

Use the @code{@@key} command for the conventional name for a key on a
keyboard, as in:

@example
@@key@{RET@}
@end example

You can use the @code{@@key} command within the argument of an
@code{@@kbd} command when the sequence of characters to be typed
includes one or more keys that are described by name.

For example, to produce @kbd{C-x @key{ESC}} and @kbd{M-@key{TAB}} you
would type:

@example
@@kbd@{C-x @@key@{ESC@}@}
@@kbd@{M-@@key@{TAB@}@}
@end example

Here is a list of the recommended names for keys:
@cindex Recommended names for keys
@cindex Keys, recommended names
@cindex Names recommended for keys
@cindex Abbreviations for keys
@cindex Control keys, specifying
@cindex Meta keys, specifying

@quotation
@table @t
@item SPC
Space
@item RET
Return
@item LFD
Linefeed (however, since most keyboards nowadays do not have a Linefeed key,
it might be better to call this character @kbd{C-j})
@item TAB
Tab
@item BS
Backspace
@item ESC
Escape
@item DELETE
Delete
@item SHIFT
Shift
@item CTRL
Control
@item META
Meta
@end table
@end quotation

@cindex META key
There are subtleties to handling words like `meta' or `ctrl' that are
names of modifier keys.  When mentioning a character in which the
modifier key is used, such as @kbd{Meta-a}, use the @code{@@kbd} command
alone; do not use the @code{@@key} command; but when you are referring
to the modifier key in isolation, use the @code{@@key} command.  For
example, write @samp{@@kbd@{Meta-a@}} to produce @kbd{Meta-a} and
@samp{@@key@{META@}} to produce @key{META}.


@node @code{@@samp}
@nodedescription Indicating a literal sequence of characters.
@subsection @code{@@samp}@{@var{text}@}

@anchor{samp}@c old name
@findex samp

Use the @code{@@samp} command to indicate text that is a literal example
or `sample' of a sequence of characters in a file, string, pattern, etc.
Enclose the text in braces.  The argument appears within single
quotation marks; in addition, it is printed in a fixed-width font.

@example
To match @@samp@{foo@} at the end of the line,
use the regexp @@samp@{foo$@}.
@end example

@noindent
produces

@quotation
To match @samp{foo} at the end of the line, use the regexp
@samp{foo$}.
@end quotation

Any time you are referring to single characters, you should use
@code{@@samp} unless @code{@@kbd} or @code{@@key} is more appropriate.
Also, you may use @code{@@samp} for entire statements in C and for entire
shell commands---in this case, @code{@@samp} often looks better than
@code{@@code}.  Basically, @code{@@samp} is a catchall for whatever is
not covered by @code{@@code}, @code{@@kbd}, @code{@@key},
@code{@@command}, etc.

Only include punctuation marks within braces if they are part of the
string you are specifying.  Write punctuation marks outside the braces
if those punctuation marks are part of the English text that surrounds
the string.  In the following sentence, for example, the commas and
period are outside of the braces:

@example
@group
In English, the vowels are @@samp@{a@}, @@samp@{e@},
@@samp@{i@}, @@samp@{o@}, @@samp@{u@}, and sometimes
@@samp@{y@}.
@end group
@end example

@noindent
This produces:

@quotation
In English, the vowels are @samp{a}, @samp{e},
@samp{i}, @samp{o}, @samp{u},  and sometimes
@samp{y}.
@end quotation


@node @code{@@verb}
@nodedescription Indicating a verbatim sequence of characters.
@subsection @code{@@verb}@{@var{char}@var{text}@var{char}@}

@anchor{verb}@c old name
@findex verb
@cindex Verbatim in-line text

@cindex Delimiter character, for verbatim
Use the @code{@@verb} command to print a verbatim sequence of
characters.

Like @LaTeX{}'s @code{\verb} command, the verbatim text can be quoted using
any unique delimiter character.  Enclose the verbatim text, including the
delimiters, in braces.  Text is printed in a fixed-width font:

@example
How many @@verb@{|@@|@}-escapes does one need to print this
@@verb@{.@@a @@b.@@c.@} string or @@verb@{+@@'e?`@{@}!`\+@} this?
@end example

@noindent
produces

@example
How many @verb{|@|}-escapes does one need to print this
@verb{.@a @b.@c.} string or @verb{+@'e?`{}!`\+} this?
@end example

This is in contrast to @code{@@samp} (see the previous section),
@code{@@code}, and similar commands; in those cases, the argument is
normal Texinfo text, where the three characters @code{@@@{@}} are
special, as usual.  With @code{@@verb}, nothing is special except the
delimiter character you choose.

The delimiter character itself may appear inside the verbatim text, as
shown above.  As another example, @samp{@@verb@{...@}} prints a single
(fixed-width) period.

It is not reliable to use @code{@@verb} inside other Texinfo
constructs.  In particular, it does not work to use @code{@@verb} in
anything related to cross-referencing, such as section titles or
figure captions.


@node @code{@@var}
@nodedescription Indicating metasyntactic variables.
@subsection @code{@@var}@{@var{metasyntactic-variable}@}

@anchor{var}@c old name
@findex var

Use the @code{@@var} command to indicate metasyntactic variables.  A
@dfn{metasyntactic variable} is something that stands for another
piece of text.  For example, you should use a metasyntactic variable
in the documentation of a function to describe the arguments that are
passed to that function.

Do not use @code{@@var} for the names of normal variables in computer
programs.  These are specific names, so @code{@@code} is correct for
them.  For example, the Emacs Lisp variable @code{texinfo-tex-command}
is not a metasyntactic variable; it is properly formatted using @code{@@code}.

Do not use @code{@@var} for environment variables either; @code{@@env}
is correct for them (see the next section).

The effect of @code{@@var} in the Info file is to change the case of
the argument to all uppercase.  In the printed manual, the argument
is output in slanted type.
@footnote{In @TeX{} output, @code{@@var} uses a slanted typewriter font
in code contexts such as @code{@@code} or @code{@@example}.  To use a
variable-width, slanted roman font in all contexts, specify @samp{@@clear
txicodevaristt} (@pxref{@code{@@set @@value}}).   This gives consistency
for parameter names whether they are in @code{@@def}, @code{@@table
@@code}, or a regular paragraph.  Note that this flag does nothing in
@LaTeX{} output.}

@need 700
For example,

@example
To delete file @@var@{filename@},
type @@samp@{rm @@var@{filename@}@}.
@end example

@noindent
produces

@quotation
To delete file @var{filename}, type @samp{rm @var{filename}}.
@end quotation

@noindent
(Note that @code{@@var} may appear inside @code{@@code},
@code{@@samp}, @code{@@file}, etc.)

Write a metasyntactic variable all in lowercase without spaces, and
use hyphens to make it more readable.  Thus, the Texinfo source for
the illustration of how to begin a Texinfo manual looks like
this:

@example
@group
\input texinfo
@@@@settitle @@var@{name-of-manual@}
@end group
@end example

@noindent
This produces:

@example
@group
\input texinfo
@@settitle @var{name-of-manual}
@end group
@end example

In some documentation styles, metasyntactic variables are shown with
angle brackets, for example:

@example
@dots{}, type rm <filename>
@end example

@noindent
However, that is not the style that Texinfo uses.

@c FIXME add a customization variable?  Add an example on how to do that
@c for HTML?
@c (You can, of course, modify the sources to @file{texinfo.tex}
@c and the Info formatting commands
@c to output the @code{<@dots{}>} format if you wish.)


@node @code{@@env}
@nodedescription Indicating environment variables.
@subsection @code{@@env}@{@var{environment-variable}@}

@anchor{env}@c old name
@findex env

Use the @code{@@env} command to indicate environment variables, as
used by many operating systems, including GNU@.  Do not use it for
@emph{meta}syntactic variables; use @code{@@var} for those (see the
previous section).

@code{@@env} is equivalent to @code{@@code} in its effects.
For example:

@example
The @@env@{PATH@} environment variable @dots{}
@end example
@noindent produces
@quotation
The @env{PATH} environment variable @dots{}
@end quotation


@node @code{@@file}
@nodedescription Indicating file names.
@subsection @code{@@file}@{@var{file-name}@}

@anchor{file}@c old name
@findex file

Use the @code{@@file} command to indicate text that is the name of a
file, buffer, or directory, or is the name of a node in Info.  You can
also use the command for file name suffixes.  Do not use @code{@@file}
for symbols in a programming language; use @code{@@code}.

@code{@@file} is equivalent to @code{code} in its effects.  For
example,

@example
The @@file@{.el@} files are in
the @@file@{/usr/local/emacs/lisp@} directory.
@end example

@noindent
produces

@quotation
The @file{.el} files are in
the @file{/usr/local/emacs/lisp} directory.
@end quotation


@node @code{@@command}
@nodedescription Indicating command names.
@subsection @code{@@command}@{@var{command-name}@}

@anchor{command}@c old name
@findex command
@cindex Command names, indicating
@cindex Program names, indicating

Use the @code{@@command} command to indicate command names, such as
@command{ls} or @command{cc}.

@code{@@command} is equivalent to @code{@@code} in its effects.
For example:

@example
The command @@command@{ls@} lists directory contents.
@end example
@noindent produces
@quotation
The command @command{ls} lists directory contents.
@end quotation

You should write the name of a program in the ordinary text font, rather
than using @code{@@command}, if you regard it as a new English word,
such as `Emacs' or `Bison'.

When writing an entire shell command invocation, as in @samp{ls -l},
you should use either @code{@@samp} or @code{@@code} at your discretion.


@node @code{@@option}
@nodedescription Indicating option names.
@subsection @code{@@option}@{@var{option-name}@}

@anchor{option}@c old name
@findex option

Use the @code{@@option} command to indicate a command-line option; for
example, @option{-l} or @option{--version} or
@option{--output=@var{filename}}.

@code{@@option} is equivalent to @code{@@code} in its effects.
For example:

@example
The option @@option@{-l@} produces a long listing.
@end example
@noindent produces
@quotation
The option @option{-l} produces a long listing.
@end quotation


@node @code{@@dfn}
@nodedescription Specifying definitions.
@subsection @code{@@dfn}@{@var{term}@}

@anchor{dfn}@c old name
@findex dfn

Use the @code{@@dfn} command to identify the introductory or defining
use of a technical term.  Use the command only in passages whose
purpose is to introduce a term which will be used again or which the
reader ought to know.  Mere passing mention of a term for the first
time does not deserve @code{@@dfn}.  The command selects a slanted font
in the printed manual, and generates double quotation marks in the Info
file.  For example:

@example
Getting rid of a file is called @@dfn@{deleting@} it.
@end example

@noindent
produces

@quotation
Getting rid of a file is called @dfn{deleting} it.
@end quotation

As a general rule, a sentence containing the defining occurrence of a
term should be a definition of the term.  The sentence does not need
to say explicitly that it is a definition, but it should contain the
information of a definition---it should make the meaning clear.


@node @code{@@abbr}
@nodedescription Indicating abbreviations.
@subsection @code{@@abbr}@{@var{abbreviation}[, @var{meaning}]@}

@anchor{abbr}@c old name
@findex abbr

@cindex Abbreviations, tagging
You can use the @code{@@abbr} command for general abbreviations.  The
abbreviation is given as the single argument in braces, as in
@samp{@@abbr@{Comput.@}}.  As a matter of style, or for particular
abbreviations, you may prefer to omit periods, as in
@samp{@@abbr@{Mr@} Stallman}.

@code{@@abbr} accepts an optional second argument, intended to be used
for the meaning of the abbreviation.

If the abbreviation ends with a lowercase letter and a period, and is
not at the end of a sentence, and has no second argument, remember to
use the @code{@@.} command (@pxref{Ending a Sentence}) to get the
correct spacing.  However, you do not have to use @code{@@.} within
the abbreviation itself; Texinfo automatically assumes periods within
the abbreviation do not end a sentence.

In output formats with an appropriate tag, such as HTML and DocBook, this tag
is used.  Otherwise, the first argument is printed as-is; if the second
argument is present, it is printed in parentheses after the
abbreviation.  For instance:

@example
@@abbr@{Comput. J., Computer Journal@}
@end example

@noindent produces:

@display
@abbr{Comput. J., Computer Journal}
@end display

For abbreviations consisting of all capital letters, you may prefer to
use the @code{@@acronym} command instead.  See the next section for
more on the usage of these two commands.


@node @code{@@acronym}
@nodedescription Indicating acronyms.
@subsection @code{@@acronym}@{@var{acronym}[, @var{meaning}]@}

@anchor{acronym}@c old name
@findex acronym

@cindex NASA, as acronym
@cindex Acronyms, tagging
You can use the @code{@@acronym} command for abbreviations written in
all capital letters, such as `@acronym{NASA}'.  The abbreviation is
given as the single argument in braces, as in
@samp{@@acronym@{NASA@}}.  As a matter of style, or for particular
acronyms, you may prefer to use periods, as in
@samp{@@acronym@{N.A.S.A.@}}.

@code{@@acronym} accepts an optional second argument, intended to be
used for the meaning of the acronym.

If the acronym is at the end of a sentence, and if there is no second
argument, remember to use the @code{@@.} or similar command
(@pxref{Ending a Sentence}) to get the correct spacing.

In @TeX{}, the acronym is printed in slightly smaller font.  In the
Info output, the argument is printed as-is.  In either format, and
in @LaTeX{} output, if the second argument is present, it is printed in
parentheses after the acronym.  In HTML and DocBook the appropriate
tag is used.

For instance (since GNU is a recursive acronym, we use
@code{@@acronym} recursively):

@example
@@acronym@{GNU, @@acronym@{GNU@}'s Not Unix@}
@end example

@noindent produces:

@display
@acronym{GNU, @acronym{GNU}'s Not Unix}
@end display

@cindex Family names, in all capitals
In some circumstances, it is conventional to print family names in all
capitals.  Don't use @code{@@acronym} for this, since a name is not an
acronym.  Use @code{@@sc} instead (@pxref{Smallcaps}).

@code{@@abbr} and @code{@@acronym} are closely related commands: they
both signal to the reader that a shortened form is being used, and
possibly give a meaning.  When choosing whether to use these two
commands, please bear the following in mind.

@itemize @minus
@item
In common English usage, acronyms are a subset of abbreviations: they
include pronounceable words like `@acronym{NATO}', `radar', and
`snafu'; some sources also include syllable acronyms like
`Usenet', hybrids like `@acronym{SIGGRAPH}', and unpronounceable
initialisms like `@acronym{FBI}'.

@item
In Texinfo, an acronym (but not an abbreviation) should consist only
of capital letters and periods, no lowercase.

@item
In @TeX{}, an acronym (but not an abbreviation) is printed in a
slightly smaller font.

@item
It usually turns out to be quite difficult and/or time-consuming to
consistently use @code{@@acronym} for all sequences of uppercase
letters.  Furthermore, it looks strange for some acronyms to be in the
normal font size and others to be smaller.  Thus, a simpler approach
you may wish to consider is to avoid @code{@@acronym} and just typeset
everything as normal text in all capitals: @samp{GNU}, producing the
output `GNU'.

@item
In general, it's not essential to use either of these commands for all
abbreviations; use your judgment.  Text is perfectly readable without
them.
@end itemize


@node @code{@@indicateurl}
@nodedescription Indicating an example URL.
@subsection @code{@@indicateurl}@{@var{uniform-resource-locator}@}

@anchor{indicateurl}@c old name
@findex indicateurl
@cindex URL @subentry indicating

Use the @code{@@indicateurl} command to indicate a uniform resource
locator on the World Wide Web.  This is purely for markup purposes and
does not produce a link you can follow (use the @code{@@url} or
@code{@@uref} command for that, @pxref{@code{@@url}}).
@code{@@indicateurl} is useful for URLs which do not actually exist.
For example:

@example
For example, the URL might be @@indicateurl@{http://example.org/path@}.
@end example

@noindent which produces:

@display
For example, the URL might be @indicateurl{http://example.org/path}.
@end display

The output from @code{@@indicateurl} is usually like that of
@code{@@samp} (@pxref{@code{@@samp}}).


@node @code{@@email}
@nodedescription Indicating an electronic mail address.
@subsection @code{@@email}@{@var{email-address}[, @var{displayed-text}]@}

@anchor{email}@c old name
@findex email

Use the @code{@@email} command to indicate an electronic mail address.
It takes one mandatory argument, the address, and one optional argument, the
text to display (the default is the address itself).

@cindex Mailto link
In Info, the address is shown in angle brackets, preceded by the text
to display if any.  In printed output, the angle brackets are omitted.  In
HTML and DocBook output, @code{@@email} produces a @samp{mailto} link.
In HTML, a @samp{mailto} link usually brings up a mail composition window.
For example:

@example
Send bug reports to @@email@{bug-texinfo@@@@gnu.org@},
suggestions to the @@email@{bug-texinfo@@@@gnu.org, same place@}.
@end example

@noindent produces

@display
Send bug reports to @email{bug-texinfo@@gnu.org},
suggestions to the @email{bug-texinfo@@gnu.org, same place}.
@end display


@node Emphasis
@nodedescription How to emphasize text.
@section Emphasizing Text
@cindex Emphasizing text

Usually, Texinfo changes the font to mark words in the text according
to the category the words belong to; an example is the @code{@@code}
command.  Most often, this is the best way to mark words.  However,
sometimes you will want to emphasize text without indicating a
category.  Texinfo has two commands to do this.  Also, Texinfo has
several commands that specify the font in which text will be output.
These commands have no effect in Info and only one of them, the
@code{@@r} command, has any regular use.


@node @code{@@emph @@strong}
@nodedescription How to emphasize text in Texinfo.
@subsection @code{@@emph}@{@var{text}@} and @code{@@strong}@{@var{text}@}

@anchor{emph & strong}@c oldname
@findex emph
@findex strong
@cindex Emphasizing text, font for

The @code{@@emph} and @code{@@strong} commands are for emphasis;
@code{@@strong} is stronger.  In printed output, @code{@@emph} produces
@emph{italics} and @code{@@strong} produces @strong{bold}.
In the Info output, @code{@@emph} surrounds the text with underscores
(@samp{_}), and @code{@@strong} puts asterisks around the text.

For example,

@example
@group
@@strong@{Caution:@} @@samp@{rm * .[^.]*@}
removes @@emph@{all@} files in the directory.
@end group
@end example

@noindent
produces the following:

@quotation
@strong{Caution}: @samp{rm * .[^.]*}
removes @emph{all} files in the directory.
@end quotation

The @code{@@strong} command is seldom used except to mark what is, in
effect, a typographical element, such as the word `Caution' in the
preceding example.

@quotation Caution
Do not use @code{@@strong} with the word @samp{Note} followed by a
space; Info will mistake the combination for a cross-reference.  Use a
phrase such as @strong{Please notice} or @strong{Caution} instead, or
the optional argument to @code{@@quotation}---@samp{Note} is allowable
there.
@end quotation


@node Smallcaps
@nodedescription How to use the small caps font.
@subsection @code{@@sc}@{@var{text}@}: The Small Caps Font
@cindex Small caps font
@findex sc

Use the @samp{@@sc} command to set text in @sc{a small caps font}
(where possible).  Write the text you want to be in small caps between
braces in lowercase, like this:

@example
Richard @@sc@{Stallman@} a commenc@'{e} le projet GNU.
@end example

@noindent
This produces:

@display
Richard @sc{Stallman} a commenc@'{e} le projet GNU.
@end display

As shown here, we recommend reserving @code{@@sc} for special cases
where you want typographic small caps; family names are one such,
especially in languages other than English, though there are no
hard-and-fast rules about such things.

@cindex @code{<small>} tag
@TeX{} typesets any uppercase letters between the braces of an
@code{@@sc} command in full-size capitals; only lowercase letters are
printed in the small caps font.  In the Info output, the argument to
@code{@@sc} is printed in all uppercase.  In HTML, the argument is
uppercased and the output marked with the @code{<small>} tag to reduce
the font size, since HTML cannot easily represent true small caps.
In @LaTeX{}, a command setting small caps fonts is output.

Overall, we recommend using standard upper- and lowercase letters
wherever possible.


@node Fonts
@nodedescription Various font commands for printed output.
@subsection Fonts for Printing
@cindex Fonts for printing

@findex fonttextsize
@cindex Font size, reducing
@cindex Reducing font size
@cindex Smaller fonts
Texinfo provides one command to change the size of the main body font
in printed output (with @file{texinfo.tex}) for a document:
@code{@@fonttextsize}.  (This command is not a good way for setting the
font size in other output formats, where it may be ignored by
@command{texi2any}---in formats such as HTML or @LaTeX{},
we recommend using format-specific features to control such details of
formatting, e.g.@: CSS or @LaTeX{} package options respectively.)

@code{@@fonttextsize} takes a single argument on the remainder of the line,
which must be either @samp{10} or @samp{11}.  For example:

@example
@@fonttextsize 10
@end example

@cindex Printing cost, reducing
The effect is to reduce the body font to a 10@dmn{pt} size (the
default is 11@dmn{pt}).  Fonts for other elements, such as sections
and chapters, are reduced accordingly.  This should only be used in
conjunction with @code{@@smallbook} (@pxref{@code{@@smallbook}}) or
similar, since 10@dmn{pt} fonts on standard paper (8.5x11 or A4) are
too small.  One reason to use this command is to save pages, and hence
printing cost, for physical books.

Texinfo does not at present have commands to switch the font family
to use, or more general size-changing commands.

Texinfo also provides a number of font commands that specify font
changes in the printed manual and (where possible) in the HTML and DocBook
output.  They have no effect in Info.  All the commands apply to a following
argument surrounded by braces.

@table @code
@findex b @r{(bold font)}
@ifset commandlookup
@findex b
@end ifset
@cindex Bold font
@item @@b
selects @b{bold} face;

@findex i @r{(italic font)}
@ifset commandlookup
@findex i
@end ifset
@cindex Italic font
@item @@i
selects an @i{italic} font;

@findex r @r{(roman font)}
@ifset commandlookup
@findex r
@end ifset
@cindex Roman font
@cindex Default font
@item @@r
selects a @r{roman} font, which is the usual font in which text is
printed.  It may or may not be seriffed.

@findex sansserif
@cindex Sans serif font
@item @@sansserif
selects a @sansserif{sans serif} font;

@findex slanted
@cindex Slanted font
@cindex Oblique font
@item @@slanted
selects a @slanted{slanted} font;

@findex t @r{(typewriter font)}
@ifset commandlookup
@findex t
@end ifset
@cindex Monospace font
@cindex Fixed-width font
@cindex Typewriter font
@item @@t
selects the @t{fixed-width}, typewriter-style font used by @code{@@code};

@end table

@ignore
(The commands with longer names were invented much later than the
others, at which time it did not seem desirable to use very short
names for such infrequently needed features.)
@end ignore

The @code{@@r} command can be useful in example-like environments, to
write comments in the standard roman font instead of the fixed-width
font.  This looks better in printed output.

For example,

@example
@group
@@lisp
(+ 2 2)    ; @@r@{Add two plus two.@}
@@end lisp
@end group
@end example

@noindent
produces

@lisp
(+ 2 2)    ; @r{Add two plus two.}
@end lisp

The @code{@@t} command can occasionally be useful for producing output in
a typewriter font where that is supported, but no distinction with
quotation marks is needed in Info or plain text.  (Compare @code{@@t@{foo@}}
producing @t{foo} with @code{@@code@{foo@}} producing @code{foo}.)  Here
are some possible reasons for using @code{@@t} instead of @code{@@code}:

@itemize @minus
@item The argument is a single character
@item There are already quotes of some kind enclosing the argument
@item It's evident from context or the argument itself that the argument
          could be computer code (e.g.@: name of a Usenet newsgroup)
@end itemize

In general, the other font commands are unlikely to be useful; they
exist primarily to make it possible to document the functionality of
specific font effects, such as in @TeX{} and related packages.


@node Quotations and Examples
@nodedescription Block quotations, examples, etc.
@chapter Quotations and Examples

Quotations and examples are blocks of text consisting of one or more
whole paragraphs that are set off from the bulk of the text and
treated differently.  They are usually indented in the output.

In Texinfo, you always begin a quotation or example by writing an
@@-command at the beginning of a line by itself, and end it by writing
an @code{@@end} command that is also at the beginning of a line by
itself.  For instance, you begin an example by writing
@code{@@example} by itself at the beginning of a line and end the
example by writing @code{@@end example} on a line by itself, at the
beginning of that line, and with only one space between the
@code{@@end} and the @code{example}.


@node Block Enclosing Commands
@nodedescription Different constructs for different purposes.
@section Block Enclosing Commands

Here is a summary of commands that enclose blocks of text, also known
as @dfn{environments}.  They're explained further in the following
sections.

@table @code
@item @@quotation
Indicate text that is quoted. The text is filled, indented (from both
margins), and printed in a roman font by default.

@item @@indentedblock
Like @code{@@quotation}, but the text is indented only on the left.

@item @@example
Illustrate code, commands, and the like. The text is printed
in a fixed-width font, and indented but not filled.

@item @@lisp
Like @code{@@example}, but specifically for illustrating Lisp code. The
text is printed in a fixed-width font, and indented but not filled.

@item @@verbatim
Mark a piece of text that is to be printed verbatim; no character
substitutions are made and all commands are ignored, until the next
@code{@@end verbatim}.  The text is printed in a fixed-width font,
and not indented or filled.  Extra spaces and blank lines are
significant, and tabs are expanded.

@item @@display
Display illustrative text.  The text is indented but not filled, and
no font is selected (so, by default, the font is roman).

@item @@format
Like @code{@@display} (the text is not filled and no font is
selected), but the text is not indented.

@item @@smallquotation
@itemx @@smallindentedblock
@itemx @@smallexample
@itemx @@smalllisp
@itemx @@smalldisplay
@itemx @@smallformat
These @code{@@small...} commands are just like their non-small
counterparts, except that they output text in a smaller font size,
where possible.

@item @@flushleft
@itemx @@flushright
Text is not filled, but is set flush with the left or right margin,
respectively.

@item @@raggedright
Text is filled, but only justified on the left, leaving the right
margin ragged.

@item @@cartouche
Highlight text, often an example or quotation, by drawing a box with
rounded corners around it.
@end table

The @code{@@exdent} command is used within the above constructs to
undo the indentation of a line.

The @code{@@noindent} command may be used after one of the above
constructs (or at the beginning of any paragraph) to prevent the
following text from being indented as a new paragraph.


@node @code{@@quotation}
@nodedescription Writing a quotation.
@section @code{@@quotation}: Block Quotations
@anchor{quotation}@c old name

@cindex Quotations
@findex quotation

The text of a quotation is processed like normal text (regular font,
text is filled) except that:

@itemize @bullet
@item
the left margin is closer to the center of the page, so the whole of the
quotation is indented; the right margin may also be closer to the center
of the page

@item
the first lines of paragraphs are indented no more than other lines; and

@item
an @code{@@author} command may be given to specify the author of the
quotation.
@end itemize

@quotation
This is an example of text written between a @code{@@quotation}
command and an @code{@@end quotation} command.  A @code{@@quotation}
command is most often used to indicate text that is excerpted from
another (real or hypothetical) printed work.
@end quotation

Write a @code{@@quotation} command as text on a line by itself.  This
line will disappear from the output.  Mark the end of the quotation
with a line beginning with and containing only @code{@@end quotation}.
The @code{@@end quotation} line will likewise disappear from the
output.

@code{@@quotation} takes one optional argument, given on the remainder
of the line.  This text, if present, is included at the beginning of
the quotation in bold or otherwise emphasized, and followed with a
@samp{:}.  For example:

@example
@@quotation Note
This is
a foo.
@@end quotation
@end example

@noindent
produces

@quotation Note
This is
a foo.
@end quotation

If the @code{@@quotation} argument is one of these English words
(case-insensitive):

@example
Caution  Important  Note  Tip  Warning
@end example

@cindex @code{<caution>} DocBook tag
@cindex @code{<important>} DocBook tag
@cindex @code{<note>} DocBook tag
@cindex @code{<tip>} DocBook tag
@cindex @code{<warning>} DocBook tag
@cindex @code{<blockquote>} DocBook tag
@noindent then the DocBook output uses corresponding special tags
(@code{<note>}, etc.)@: instead of the default @code{<blockquote>}.

If the author of the quotation is specified in the @code{@@quotation}
block with the @code{@@author} command, a line with the author name is
displayed after the quotation:

@example
@@quotation
People sometimes ask me if it is a sin in the Church of Emacs to use
vi.  Using a free version of vi is not a sin; it is a penance.  So happy
hacking.

@@author Richard Stallman
@@end quotation
@end example

@noindent
produces

@quotation
People sometimes ask me if it is a sin in the Church of Emacs to use
vi.  Using a free version of vi is not a sin; it is a penance.  So happy
hacking.

@author Richard Stallman
@end quotation


@node @code{@@indentedblock}
@nodedescription Block of text indented on left.
@section @code{@@indentedblock}: Indented text blocks
@cindex Indented text block
@findex indentedblock

The @code{@@indentedblock} environment is similar to
@code{@@quotation}, except that text is only indented on the left (and
there is no optional argument for an author).  Thus, the text font
remains unchanged, and text is gathered and filled as usual, but the
left margin is increased.  For example:

@indentedblock
This is an example of text written between an @code{@@indentedblock}
command and an @code{@@end indentedblock} command.  The
@code{@@indentedblock} environment can contain any text or other
commands desired.
@end indentedblock

This is written in the Texinfo source as:

@example
@@indentedblock
This is an example ...
@@end indentedblock
@end example


@node @code{@@example}
@nodedescription Writing an example in a fixed-width font.
@section @code{@@example}: Example Text

@anchor{example}@c old name
@findex example
@cindex Examples, formatting them
@cindex Formatting examples

The @code{@@example} environment is used to indicate
computer input or output that is not part of the running text. If you
want to embed code fragments within sentences, use the @code{@@code}
command or its relatives instead (@pxref{@code{@@code}}).

Write an @code{@@example} command at the beginning of a line by
itself.  Mark the end of the block with @code{@@end example}.
For example,

@example
@@example
cp foo @@var@{dest1@}; \
 cp foo @@var@{dest2@}
@@end example
@end example

@noindent
produces

@example
cp foo @var{dest1}; \
 cp foo @var{dest2}
@end example

The output uses a fixed-width font and is indented.  Each line
in the input file is a line in the output; that is, the source
text is not filled.  Extra spaces and blank lines are significant.
Texinfo commands @emph{are} expanded; if you want the output to be
the input verbatim, use the @code{@@verbatim} environment instead
(@pxref{@code{@@verbatim}}).

Examples are often, logically speaking, ``in the middle'' of a
paragraph, and the text that continues afterwards should not be
indented, as in the example above.  The @code{@@noindent} command
prevents a piece of text from being indented as if it were a new
paragraph (@pxref{@code{@@noindent}}).

If you wish to use the normal roman font for a code comment, you can
use the @code{@@r} command (@pxref{Fonts}).

You may optionally give arguments to the @code{@@example} command,
separated by commas if there is more than one.  In the HTML output,
any such arguments are output as class names, prefixed by the string
@samp{user-}.  This may be useful for adding syntax highlighting to
manuals for code samples.

We recommend that when you give multiple arguments to @code{@@example}, you
use the first argument to specify the language of the code (e.g.@:
@samp{C}, @samp{lisp}, @samp{Cplusplus}).  You may find uses for other
arguments, such as providing a formatting hint or marking code samples
for extraction and further processing, but for now nothing definitive
is recommended.  Perhaps this will change in future Texinfo releases.

@quotation Caution
Do not use tabs in the lines of an example!  (Or anywhere else in
Texinfo, except in verbatim environments.)  @TeX{} treats a tab as a
single space character, so any text following a tab on a line will not
be aligned as expected.
@end quotation


@node @code{@@verbatim}
@nodedescription Writing a verbatim example.
@section @code{@@verbatim}: Literal Text

@anchor{verbatim}@c old name
@findex verbatim
@cindex Verbatim environment

Use the @code{@@verbatim} environment for printing of text that may
contain special characters or commands that should not be interpreted,
such as computer input or output (@code{@@example} interprets its text
as regular Texinfo commands).  This is especially useful for including automatically
generated files in a Texinfo manual.

In general, the output will be just the same as the input.  No
character substitutions are made, e.g., all spaces and blank lines are
significant, including tabs.  The text is typeset in a fixed-width font,
and not indented or filled.

Write a @code{@@verbatim} command at the beginning of a line by
itself.  This line will disappear from the output.  Mark the end of
the verbatim block with an @code{@@end verbatim} command, also written
at the beginning of a line by itself.  The @code{@@end verbatim} will
also disappear from the output.

For example:

@example
@@verbatim
@{
@var{<tab>}@@command with strange characters: @@'e
expand@var{<tab>}me
@}
@@end verbatim
@end example

@noindent
(where @var{<tab>} stands for a literal tab character).  This produces:

@verbatim
{
	@command with strange characters: @'e
expand	me
}
@end verbatim

Since the lines containing @code{@@verbatim} and @code{@@end verbatim}
produce no output, typically you should put a blank line before the
@code{@@verbatim} and another blank line after the @code{@@end
verbatim}.  Blank lines between the beginning @code{@@verbatim} and
the ending @code{@@end verbatim} will appear in the output.

@cindex Verbatim, small
@cindex Small verbatim
You can get a ``small'' verbatim by enclosing the @code{@@verbatim} in
an @code{@@smallformat} environment, as shown here:

@example
@@smallformat
@@verbatim
... still verbatim, but in a smaller font ...
@@end verbatim
@@end smallformat
@end example

Finally, a word of warning: it is not reliable to use
@code{@@verbatim} inside other Texinfo constructs.

See also @ref{@code{@@verbatiminclude}}.


@node @code{@@lisp}
@nodedescription Illustrating Lisp code.
@section @code{@@lisp}: Marking a Lisp Example

@anchor{lisp}@c old name
@findex lisp
@cindex Lisp example

The @code{@@lisp} command is very similar to @code{@@example},
but marks the contents as Lisp code.  For example:

@example
@@lisp
Example lisp code
@@end lisp
@end example

@noindent
The programming language can also be given as an argument to the
@code{@@example} command (@pxref{@code{@@example}}), so the example
above could also be written as:

@example
@@example lisp
Example lisp code
@@end example
@end example

Use @code{@@lisp} to preserve information regarding the nature of
the example.  This is useful, for example, if you write a function
that evaluates only and all the Lisp code in a Texinfo file.  Then you
can use the Texinfo file as a Lisp library.


@node @code{@@display}
@nodedescription Writing an example in the current font.
@section @code{@@display}: Examples Using the Text Font

@anchor{display}@c old name
@findex display
@cindex Display formatting

The @code{@@display} command begins another kind of environment, where
the font is left unchanged, not switched to typewriter as with
@code{@@example}.  Each line of input still produces a line of output,
and the output is still indented.

@display
This is an example of text written between a @code{@@display} command
and an @code{@@end display} command.  The @code{@@display} command
indents the text, but does not fill it.
@end display


@node @code{@@format}
@nodedescription Writing an example without narrowed margins.
@section @code{@@format}: Examples Using the Full Line Width

@anchor{format}@c old name
@findex format

The @code{@@format} command is similar to @code{@@display}, except it
leaves the text unindented.  Like @code{@@display}, it does not select
the fixed-width font.  Thus,

@example
@group
@@format
This is an example of text written between a @@code@{@@@@format@} command
and an @@code@{@@@@end format@} command.  As you can see
from this example,
the @@code@{@@@@format@} command does not fill the text.
@@end format
@end group
@end example

@noindent
produces

@format
@group
This is an example of text written between a @code{@@format} command
and an @code{@@end format} command.  As you can see
from this example,
the @code{@@format} command does not fill the text.
@end group
@end format


@node @code{@@exdent}
@nodedescription Undo indentation on a line.
@section @code{@@exdent}: Undoing a Line's Indentation

@anchor{exdent}@c old name
@findex exdent
@cindex Indentation undoing

The @code{@@exdent} command removes any indentation a line might have.
The command is written at the beginning of a line and applies only to
the text that follows the command that is on the same line.  Do not use
braces around the text.  The text on an @code{@@exdent} line is also
printed in the roman font where the output format allows this.

@code{@@exdent} is usually used within examples.  Thus,

@example
@group
@@example
This line follows an @@@@example command.
@@exdent This line is exdented.
This line follows the exdented line.
The @@@@end example comes on the next line.
@@end example
@end group
@end example

@noindent
produces

@example
@group
This line follows an @@example command.
@exdent This line is exdented.
This line follows the exdented line.
The @@end example comes on the next line.
@end group
@end example

In practice, the @code{@@exdent} command is rarely used.  Usually, you
un-indent text by ending the example and returning the page to its
normal width.

@code{@@exdent} does not have an effect in all output formats.



@node @code{@@flushleft @@flushright}
@nodedescription Pushing text flush left or flush right.
@section @code{@@flushleft} and @code{@@flushright}

@anchor{flushleft & flushright}@c old name
@findex flushleft
@findex flushright
@cindex Ragged right, without filling
@cindex Ragged left, without filling

The @code{@@flushleft} and @code{@@flushright} commands line up the
ends of lines on the left and right margins of a page,
but do not fill the text.  The commands are written on lines of their
own, without braces.  The @code{@@flushleft} and @code{@@flushright}
commands are ended by @code{@@end flushleft} and @code{@@end
flushright} commands on lines of their own.

@need 1500
For example,

@example
@group
@@flushleft
This text is
written flushleft.
@@end flushleft
@end group
@end example

@noindent
produces

@quotation
@flushleft
This text is
written flushleft.
@end flushleft
@end quotation


@code{@@flushright} produces the type of indentation often used in the
return address of letters.  For example,

@example
@group
@@flushright
Here is an example of text written
flushright.  The @@code@{@@flushright@} command
right justifies every line but leaves the
left end ragged.
@@end flushright
@end group
@end example

@noindent
produces

@flushright
Here is an example of text written
flushright.  The @code{@@flushright} command
right justifies every line but leaves the
left end ragged.
@end flushright


@node @code{@@raggedright}
@nodedescription Avoiding justification on the right.
@section @code{@@raggedright}: Ragged Right Text

@anchor{raggedright}@c old name
@findex raggedright
@cindex Ragged right, with filling

The @code{@@raggedright} fills text as usual, but the text is only
justified on the left; the right margin is ragged.  The command is
written on a line of its own, without braces.  The
@code{@@raggedright} command is ended by @code{@@end raggedright} on a
line of its own.  This command only has an effect in output
formats where text is justified on the left, but
not in output formats where text is always set ragged right, such as
Info or HTML.

The @code{@@raggedright} command can be useful with paragraphs
containing lists of commands with long names, when it is known in
advance that justifying the text on both margins will make the
paragraph look bad.

An example (from elsewhere in this manual):

@example
@group
@@raggedright
Commands for double and single angle quotation marks:
@@code@{@@@@guillemetleft@@@{@@@}@}, @@code@{@@@@guillemetright@@@{@@@}@},
@@code@{@@@@guillemotleft@@@{@@@}@}, @@code@{@@@@guillemotright@@@{@@@}@},
@@code@{@@@@guilsinglleft@@@{@@@}@}, @@code@{@@@@guilsinglright@@@{@@@}@}.
@@end raggedright
@end group
@end example

@noindent
produces

@raggedright
Commands for double and single angle quotation marks:
@code{@@guillemetleft@{@}}, @code{@@guillemetright@{@}},
@code{@@guillemotleft@{@}}, @code{@@guillemotright@{@}},
@code{@@guilsinglleft@{@}}, @code{@@guilsinglright@{@}}.
@end raggedright


@node @code{@@noindent}
@nodedescription Preventing paragraph indentation.
@section @code{@@noindent}: Omitting Indentation

@anchor{noindent}@c old name
@findex noindent
@cindex Omitting indentation
@cindex Suppressing indentation
@cindex Indentation, omitting

An example or other inclusion can break a paragraph into segments.
Ordinarily, the formatters indent text that follows an example as a new
paragraph.  You can prevent this on a case-by-case basis by writing
@code{@@noindent} at the beginning of a line, preceding the continuation
text.  You can also disable indentation for all paragraphs globally with
@code{@@paragraphindent} (@pxref{@code{@@paragraphindent}}).

Here is an example showing how to eliminate the normal indentation of
the text after an @code{@@example}, a common situation:

@example
@group
@@example
This is an example
@@end example

@@noindent
This line is not indented.  As you can see, the
beginning of the line is fully flush left with the
line that follows after it.
@end group
@end example

@noindent produces:

@display
@example
This is an example
@end example

@noindent
This line is not indented.  As you can see, the
beginning of the line is fully flush left with the
line that follows after it.
@end display

The standard usage of @code{@@noindent} is just as above: at the
beginning of what would otherwise be a paragraph, to eliminate the
indentation that normally happens there.  It can either be followed by
text or be on a line by itself.  There is no reason to use it
in other contexts, such as in the middle of a paragraph or inside an
environment (@pxref{Quotations and Examples}).

You can control the number of blank lines in the Info file output by
adjusting the input as desired: a line containing just
@code{@@noindent} does not generate a blank line, and neither does an
@code{@@end} line for an environment.

Do not put braces after a @code{@@noindent} command; they are not
used, since @code{@@noindent} is a command used outside of paragraphs
(@pxref{Command Syntax}).


@node @code{@@indent}
@nodedescription Forcing paragraph indentation.
@section @code{@@indent}: Forcing Indentation

@anchor{indent}@c old name
@findex indent
@cindex Forcing indentation
@cindex Inserting indentation
@cindex Indentation, forcing

@indent
To complement the @code{@@noindent} command (see the previous
section), Texinfo provides the @code{@@indent} command to force a
paragraph to be indented.  For instance, this paragraph (the first in
this section) is indented using an @code{@@indent} command.

And indeed, the first paragraph of a section is the most likely place
to use @code{@@indent}, to override the normal behavior of no
indentation there (@pxref{@code{@@paragraphindent}}).  It can either be
followed by text or be on a line by itself.

As a special case, when @code{@@indent} is used in an environment
where text is not filled, it produces a paragraph indentation space in
the @TeX{} output.  (These environments are where a line of input
produces a line of output, such as @code{@@example} and
@code{@@display}; for a summary of all environments, @pxref{Block
Enclosing Commands}.)

Do not put braces after an @code{@@indent} command; they are not used,
since @code{@@indent} is a command used outside of paragraphs
(@pxref{Command Syntax}).


@node @code{@@cartouche}
@nodedescription Drawing rounded rectangles around text.
@section @code{@@cartouche}: Rounded Rectangles

@anchor{cartouche}@c old name
@findex cartouche
@cindex Box with rounded corners
@cindex Rounded rectangles, around text

Where the output format allows, the @code{@@cartouche} command draws a
box with rounded corners around its contents.  You can use this command
to isolate a portion of the manual from the main flow.  You can also
further highlight an example or quotation with @code{@@cartouche}.

For instance, you could write a manual in which one type of example is
surrounded by a cartouche for emphasis.  For example,

@example
@@cartouche
@@example
% pwd
/usr/local/share/emacs
@@end example
@@end cartouche
@end example

@noindent
surrounds the two-line example with a box with rounded corners, in the
printed manual.

The output from the example looks like this (if you're reading this in
Info, you'll see the @code{@@cartouche} had no effect):

@cartouche
@example
% pwd
/usr/local/share/emacs
@end example
@end cartouche

@code{@@cartouche} takes one optional argument, given on the remainder
of the line.  This text, if present, is the cartouche title.  It is
output in bold or otherwise emphasized at the beginning of the cartouche,
and is centered in some output formats.

The following example illustrates a cartouche with a title:

@example
@@cartouche Important
Text explaining something important out of the main
flow of the text.
@@end cartouche
@end example

The cartouche with a title looks like this:

@cartouche Important
Text explaining something important out of the main
flow of the text.
@end cartouche

A cartouche is output on a single page in printed output, similarly to
@code{@@group} (@pxref{@code{@@group}}).


@node small
@nodedescription Examples in a smaller font.
@section @code{@@small@dots{}} Block Commands

@findex smallexample
@findex smallformat
@findex smalllisp
@findex smallquotation
@findex smalldisplay
@findex smallindentedblock
@cindex Small examples
@cindex Examples in smaller fonts
@cindex Quotations in smaller fonts
@cindex Lisp examples in smaller fonts

In addition to the regular @code{@@example} and similar commands,
Texinfo has ``small'' example-style commands.  These are
@code{@@smallquotation}, @code{@@smallindentedblock},
@code{@@smalldisplay}, @code{@@smallexample}, @code{@@smallformat},
and @code{@@smalllisp}.

In most output formats, the @code{@@small@dots{}} commands are
equivalent to their non-small companion commands.

In printed output, however, the @code{@@small@dots{}} commands typeset text in
a smaller font than the non-small example commands.  Thus, for
instance, code examples can contain longer lines and still fit on a
page without needing to be rewritten.

Mark the end of a @code{@@small@dots{}} block with a corresponding
@code{@@end small@dots{}}.  For example, pair @code{@@smallexample} with
@code{@@end smallexample}.

Here is an example of the font used by the @code{@@smallexample}
command (in most output formats, the output will be the same as usual):

@smallexample
@dots{} to make sure that you have the freedom to
distribute copies of free software (and charge for
this service if you wish), that you receive source
code or can get it if you want it, that you can
change the software or use pieces of it in new free
programs; and that you know you can do these things.
@end smallexample

The @code{@@small@dots{}} commands use the same font style as their
normal counterparts: @code{@@smallexample} and @code{@@smalllisp} use
a fixed-width font, and everything else uses the regular font.
They also have the same behavior in other respects---whether filling
is done and whether margins are narrowed.  They do not take arguments
even when their normal counterparts do, however.

@vindex dispenvsize
As a general rule, it's better to just use the regular
commands (such as @code{@@example} instead of @code{@@smallexample}),
unless you have a good reason for it.  When processing with
@file{texinfo.tex} only, you can obtain a similar effect with
@samp{@@set dispenvsize small}, which uses a smaller font for
@code{@@example} and other environments.  In HTML output, you can
use CSS to change the font size of environments if needed; @pxref{HTML CSS}.


@node Lists and Tables
@nodedescription Itemized or numbered lists, and tables.
@chapter Lists and Tables
@cindex Making lists and tables
@cindex Lists and tables, making
@cindex Tables and lists, making

Texinfo has several ways of making lists and tables.  Lists can be
bulleted or numbered; two-column tables can highlight the items in
the first column; multi-column tables are also supported.


@node Introducing Lists
@nodedescription Texinfo formats lists for you.
@section Introducing Lists

Texinfo automatically indents the text in lists or tables, and numbers
an enumerated list.  This last feature is useful if you modify the
list, since you do not need to renumber it yourself.

Numbered lists and tables begin with the appropriate @@-command at the
beginning of a line, and end with the corresponding @code{@@end}
command on a line by itself.  The table and itemized-list commands
also require that you write formatting information on the same line as
the beginning @@-command.

Begin an enumerated list, for example, with an @code{@@enumerate}
command and end the list with an @code{@@end enumerate} command.
Begin an itemized list with an @code{@@itemize} command, followed on
the same line by a formatting command such as @code{@@bullet}, and end
the list with an @code{@@end itemize} command.

Precede each element of a list with an @code{@@item} or @code{@@itemx}
command.

@sp 1
@noindent
Here is an itemized list of the different kinds of table and lists:

@itemize @bullet{}
@item
Itemized lists with and without bullets.

@item
Enumerated lists, using numbers or letters.

@item
Two-column tables with highlighting.
@end itemize

@sp 1
@noindent
Here is an enumerated list with the same items:

@enumerate
@item
Itemized lists with and without bullets.

@item
Enumerated lists, using numbers or letters.

@item
Two-column tables with highlighting.
@end enumerate

@sp 1
@noindent
And here is a two-column table with the same items and their
@w{@@-commands}:

@table @code
@item @@itemize
Itemized lists with and without bullets.

@item @@enumerate
Enumerated lists, using numbers or letters.

@item @@table
@itemx @@ftable
@itemx @@vtable
Two-column tables, optionally with indexing.
@end table


@node @code{@@itemize}
@nodedescription How to construct a simple list.
@section @code{@@itemize}: Making an Itemized List

@anchor{itemize}@c old name
@findex itemize
@cindex Itemization

The @code{@@itemize} command produces a sequence of ``items'', each
starting with a bullet or other mark inside the left margin, and
generally indented.

Begin an itemized list by writing @code{@@itemize} at the beginning of
a line.  Follow the command, on the same line, with a Texinfo command
or character to generate a mark.  Usually, you will use @code{@@bullet}
after @code{@@itemize}, but you can use @code{@@minus}, or any other
Texinfo command or character.  If you don't specify a mark command,
the default is @code{@@bullet}.

@findex item @r{in @code{@@itemize}}
After the @code{@@itemize}, write your items, each starting with
@code{@@item}.  Text can follow on the same line as the @code{@@item}.
The text of an item can continue for more than one paragraph.

Here is an example of the use of @code{@@itemize}:

@example
@group
@@itemize @@bullet@{@}
@@item
Some text for foo.

@@item
Some text
for bar.
@@end itemize
@end group
@end example

@noindent
This produces:

@quotation
@itemize @bullet{}
@item
Some text for foo.

@item
Some text
for bar.
@end itemize
@end quotation

When you give a mark command such as @code{@@bullet} as the argument
to @code{@@itemize} command, you may omit the @samp{@{@}} that would
normally follow the command.

@cindex @code{@@w}, for blank items
If you don't want any mark at all, but still want logical items, use
@code{@@w@{@}} (in this case the braces are required).

There should be at least one @code{@@item} inside the @code{@@itemize}
environment.  If none are present, @code{texi2any} gives a warning.
If you just want indented text and not a list of items, use
@code{@@indentedblock}; @pxref{@code{@@indentedblock}}.

Index entries that occur immediately before an @code{@@item}
are associated with the @code{@@item}.

Usually, you should put a blank line between items.  This puts a blank
line in the Info file. (@TeX{} inserts the proper vertical space in
any case.)  Except when the entries are very brief, these blank lines
make the list look better.

Itemized lists may be embedded within other itemized lists.  Here is a
list marked with dashes embedded in a list marked with bullets:

@example
@group
@@itemize @@bullet@{@}
@@item
First item.

@@itemize @@minus@{@}
@@item
Inner item.

@@item
Second inner item.
@@end itemize

@@item
Second outer item.
@@end itemize
@end group
@end example

@noindent
This produces:

@quotation
@itemize @bullet{}
@item
First item.

@itemize @minus{}
@item
Inner item.

@item
Second inner item.
@end itemize

@item
Second outer item.
@end itemize
@end quotation


@node @code{@@enumerate}
@nodedescription How to construct a numbered list.
@section @code{@@enumerate}: Making a Numbered or Lettered List

@anchor{enumerate}@c old name
@findex enumerate
@cindex Enumeration

@code{@@enumerate} is like @code{@@itemize} (@pxref{@code{@@itemize}}),
except that the labels on the items are successive integers or letters
instead of bullets.

Write the @code{@@enumerate} command at the beginning of a line.  The
command does not require an argument, but accepts either a number or a
letter as an option.  Without an argument, @code{@@enumerate} starts the
list with the number @samp{1}.  With a numeric argument, such as
@samp{3}, the command starts the list with that number.  With an upper-
or lowercase letter, such as @samp{a} or @samp{A}, the command starts
the list with that letter.

Write the text of the enumerated list in the same way as an itemized
list: write a line starting with @code{@@item} at the beginning of
each item in the enumeration.  It is ok to have text following the
@code{@@item}, and the text for an item can continue for several
paragraphs.

You should put a blank line between entries in the list.
This generally makes it easier to read the Info file.

@need 1500
Here is an example of @code{@@enumerate} without an argument:

@example
@group
@@enumerate
@@item
Underlying causes.

@@item
Proximate causes.
@@end enumerate
@end group
@end example

@noindent
This produces:

@enumerate
@item
Underlying causes.

@item
Proximate causes.
@end enumerate
@sp 1
Here is an example with an argument of @kbd{3}:
@sp 1
@example
@group
@@enumerate 3
@@item
Predisposing causes.

@@item
Precipitating causes.

@@item
Perpetuating causes.
@@end enumerate
@end group
@end example

@noindent
This produces:

@enumerate 3
@item
Predisposing causes.

@item
Precipitating causes.

@item
Perpetuating causes.
@end enumerate
@sp 1
Here is a summary:
@sp 1
@enumerate a
@item
@code{@@enumerate}

Without an argument, produce a numbered list, with the first item
numbered@tie{}1.

@item
@code{@@enumerate @var{unsigned-integer}}

With an (unsigned) numeric argument, start a numbered list with that
number.  You can use this to continue a list that you interrupted with
other text.

@item
@code{@@enumerate @var{uppercase-letter}}

With an uppercase letter as argument, start a list
in which each item is marked
by a letter, beginning with that uppercase letter.

@item
@code{@@enumerate @var{lowercase-letter}}

With a lowercase letter as argument, start a list
in which each item is marked by
a letter, beginning with that lowercase letter.
@end enumerate

You can also nest enumerated lists, as in an outline.


@node Two-column Tables
@nodedescription How to construct a two-column table.
@section Making a Two-column Table

@cindex Tables, making two-column
@findex table

@code{@@table} is similar to @code{@@itemize}
(@pxref{@code{@@itemize}}), but allows you to specify a name or
heading line for each item.  The @code{@@table} command is used to
produce two-column tables, and is especially useful for glossaries,
explanatory exhibits, and command-line option summaries.


@node @code{@@table}
@nodedescription How to construct a two-column table.
@subsection Using the @code{@@table} Command

@anchor{table}@c old name

@cindex Definition lists, typesetting
Use the @code{@@table} command to produce a two-column table.  This 
command is typically used when you have a list of items and a brief text 
with each one, such as a list of definitions.

Write the @code{@@table} command at the beginning of a line, after a
blank line, and follow it on the same line with an argument that is an
`indicating' command, such as @code{@@code}, @code{@@samp},
@code{@@var}, @code{@@option}, or @code{@@kbd} (@pxref{Indicating}).
This command will be applied to the text in the first column.  For 
example, @code{@@table @@code} will cause the text in the first column 
to be output as if it had been the argument to a @code{@@code} command.

@anchor{@code{@@asis}}@c command name with @, for consistency
@findex asis
You may use the @code{@@asis} command as an argument to
@code{@@table}.  @code{@@asis} is a command that does nothing: if you
use this command after @code{@@table}, the first column entries are
output without added highlighting (``as is'').

The @code{@@table} command works with other commands besides those
explicitly mentioned here.  However, you can only use predefined
Texinfo commands that take an argument in braces.  You cannot
reliably use a new command defined with @code{@@macro}, although an
@code{@@alias} (for a suitable predefined command) is acceptable.
@xref{Defining New Texinfo Commands}.

@findex item @r{in @code{@@table}}
Begin each table entry with an @code{@@item} command at the beginning
of a line.  Write the text for the first column on the same line as the
@code{@@item} command.  Write the text for the second column on the line
following the @code{@@item} line and on subsequent lines.  You may
write as many lines of supporting text as you wish, even several
paragraphs.  But only the text on the same line as the @code{@@item}
will be placed in the first column (including any footnotes).
You do not need to type anything for an empty second column.

Normally, you should put a blank line between table entries.  This puts
a blank line in the Info file, which looks better unless the entries
are very brief.

End the table with a line consisting of @code{@@end table}.
Follow the end of the table by a blank line for consistent formatting
across output formats.

@c TeX aloways starts a new paragraph after the table

@need 1500
For example, the following table highlights the text in the first
column with the @code{@@samp} command:

@example
@group
@@table @@samp
@@item foo
This is the text for
@@samp@{foo@}.

@@item bar
Text for @@samp@{bar@}.
@@end table
@end group
@end example

@noindent
This produces:

@table @samp
@item foo
This is the text for
@samp{foo}.

@item bar
Text for @samp{bar}.
@end table

If you want to list two or more named items with a single block of
text, use the @code{@@itemx} command.  (@xref{@code{@@itemx}}.)

The @code{@@table} command (@pxref{@code{@@table}}) is not supported
inside @code{@@display}.  Since @code{@@display} is line-oriented, it
doesn't make sense to use them together.  If you want to indent a
table, try @code{@@quotation} (@pxref{@code{@@quotation}}) or
@code{@@indentedblock} (@pxref{@code{@@indentedblock}}).


@node @code{@@ftable @@vtable}
@nodedescription Automatic indexing for two-column tables.
@subsection @code{@@ftable} and @code{@@vtable}

@anchor{ftable vtable}@c old name
@findex ftable
@findex vtable
@cindex Tables with indexing
@cindex Indexing table entries automatically

The @code{@@ftable} and @code{@@vtable} commands are the same as the
@code{@@table} command except that @code{@@ftable} automatically enters
each of the items in the first column of the table into the index of
functions and @code{@@vtable} automatically enters each of the items in
the first column of the table into the index of variables.  This
simplifies the task of creating indices.  Only the items on the same
line as the @code{@@item} or @code{@@itemx} commands are indexed, and
they are indexed in exactly the form that they appear on that line.
@xref{Indices}, for more information about indices.

Begin a two-column table using @code{@@ftable} or @code{@@vtable} by
writing the @@-command at the beginning of a line, followed on the same
line by an argument that is a Texinfo command such as @code{@@code},
exactly as you would for a @code{@@table} command; and end the table
with an @code{@@end ftable} or @code{@@end vtable} command on a line by
itself.

See the example for @code{@@table} in the previous section.


@node @code{@@itemx}
@nodedescription How to put more entries in the first column.
@subsection @code{@@itemx}: Second and Subsequent Items

@anchor{itemx}@c old name
@cindex Two named items for @code{@@table}
@findex itemx

Use the @code{@@itemx} command inside a table when you have two or more
first column entries for the same item, each of which should appear on a
line of its own.

Use @code{@@item} for the first entry, and @code{@@itemx} for all
subsequent entries; @code{@@itemx} must always follow an @code{@@item}
command, with no blank line intervening.

The @code{@@itemx} command works exactly like @code{@@item} except that
it does not generate extra vertical space above the first column text in some
output formats.  If you have multiple consecutive @code{@@itemx} commands, do
not insert any blank lines between them.

For example,

@example
@group
@@table @@code
@@item upcase
@@itemx downcase
These two functions accept a character or a string as
argument, and return the corresponding uppercase (lowercase)
character or string.
@@end table
@end group
@end example

@noindent
This produces:

@table @code
@item upcase
@itemx downcase
These two functions accept a character or a string as
argument, and return the corresponding uppercase (lowercase)
character or string.
@end table

@noindent
(Note also that this example illustrates multi-line supporting text in
a two-column table.)


@node Multi-column Tables
@nodedescription How to construct generalized tables.
@section @code{@@multitable}: Multi-column Tables

@findex multitable
@cindex Tables, making multi-column

@code{@@multitable} allows you to construct tables with any number of
columns, with each column having any width you like.

You define the column widths on the @code{@@multitable} line itself, and
write each row of the actual table following an @code{@@item} command,
with columns separated by a @code{@@tab} command.  Finally, @code{@@end
multitable} completes the table.  Details in the sections below.


@node Multitable Column Widths
@nodedescription Defining multitable column widths.
@subsection Multitable Column Widths
@cindex Multitable column widths
@cindex Column widths, defining for multitables
@cindex Widths, defining multitable column

You can define the column widths for a multitable in two ways: as
fractions of the line length; or with a prototype row.  Mixing the two
methods is not supported.  In either case, the widths are defined
entirely on the same line as the @code{@@multitable} command.

@enumerate
@item
@findex columnfractions
@cindex Line length, column widths as fraction of
To specify column widths as fractions of the line length, write
@code{@@columnfractions} and the decimal numbers (presumably less than
1; a leading zero is allowed and ignored) after the
@code{@@multitable} command, as in:

@example
@@multitable @@columnfractions .33 .33 .33
@end example

The fractions need not add up exactly to 1.0, as these do not.  This
allows you to produce tables that do not need the full line length.

When using @code{@@columnfractions}, the leftmost column may appear
slightly wider than you might expect, relative to the other columns.
This is due to spacing between columns being included in the width of
the other columns.

@item
@cindex Prototype row, column widths defined by
To specify a prototype row, write the longest entry for each column
enclosed in braces after the @code{@@multitable} command.  For example:

@example
@@multitable @{some text for column one@} @{for column two@}
@end example

@noindent
The first column will then have the width of the typeset `some text for
column one', and the second column the width of `for column two'.

The prototype entries need not appear in the table itself.

Although we used simple text in this example, the prototype entries can
contain Texinfo commands; markup commands such as @code{@@code} are
particularly likely to be useful.

Prototype rows have no effect in HTML output.

@end enumerate


@node Multitable Rows
@nodedescription Defining multitable rows, with examples.
@subsection Multitable Rows

@cindex Multitable rows
@cindex Rows, of a multitable

@findex item @r{in @code{@@multitable}}
@findex tab
After the @code{@@multitable} command defining the column widths (see
the previous section), you begin each row in the body of a multitable
with @code{@@item}, and separate the column entries with @code{@@tab}.
Line breaks are not special within the table body, and you may break
input lines in your source file as necessary.

@findex headitem
@cindex Heading row, in table
@cindex @code{<thead>} HTML/DocBook tag
You can also use @code{@@headitem} instead of @code{@@item} to produce
a @dfn{heading row}.  The @TeX{} output for such a row is in bold, and
the HTML and DocBook output uses the @code{<thead>} tag.  In Info, the
heading row is followed by a separator line made of dashes (@samp{-}
characters).

@findex headitemfont
@cindex Font for multitable heading rows
The command @code{@@headitemfont} can be used in templates when the
entries in a @code{@@headitem} row need to be used in a template.  It
is a synonym for @code{@@b}, but using @code{@@headitemfont} avoids
any dependency on that particular font style, in case we provide a way
to change it in the future.

Here is a complete example of a multi-column table (the text is from
@cite{The GNU Emacs Manual}, @pxref{Split Window,, Splitting Windows,
emacs, The GNU Emacs Manual}):

@example
@@multitable @@columnfractions .15 .45 .4
@@headitem Key @@tab Command @@tab Description
@@item C-x 2
@@tab @@code@{split-window-vertically@}
@@tab Split the selected window into two windows,
with one above the other.
@@item C-x 3
@@tab @@code@{split-window-horizontally@}
@@tab Split the selected window into two windows
positioned side by side.
@@item C-Mouse-2
@@tab
@@tab In the mode line or scroll bar of a window,
split that window.
@@end multitable
@end example

@noindent produces:

@multitable @columnfractions .15 .45 .4
@headitem Key @tab Command @tab Description
@item C-x 2
@tab @code{split-window-vertically}
@tab Split the selected window into two windows,
with one above the other.
@item C-x 3
@tab @code{split-window-horizontally}
@tab Split the selected window into two windows
positioned side by side.
@item C-Mouse-2
@tab
@tab In the mode line or scroll bar of a window,
split that window.
@end multitable


@node Special Displays
@nodedescription Floating figures and footnotes.
@chapter Special Displays
@cindex Special displays

The commands in this chapter allow you to write text that is specially
displayed (output format permitting), outside of the normal document
flow.

One set of such commands is for creating ``floats'', that is, figures,
tables, and the like, set off from the main text, possibly numbered,
captioned, and/or referred to from elsewhere in the document.  Images
are often included in these displays.

Another group of commands is for creating footnotes in Texinfo.


@node Floats
@nodedescription Figures, tables, and the like.
@section Floats
@cindex Floats

A @dfn{float} is a display which is set off from the main text.  It is
typically labeled as being a ``Figure'', ``Table'', ``Example'', or
some similar type.

@cindex Floating, not yet implemented
A float is so-named because, in principle, it can be moved to the
bottom or top of the current page, or to a following page, in the
printed output.  (Floating does not make sense in other output
formats.)  In every output format except for @LaTeX{}, however,
this floating is unfortunately not yet implemented.  Instead, the
floating material is simply output at the current location, more
or less as if it were an @code{@@group} (@pxref{@code{@@group}}).


@node @code{@@float}
@nodedescription Producing floating material.
@subsection @code{@@float} [@var{type}][,@var{label}]: Floating Material

@anchor{float}@c old name
@findex float
@cindex Float environment

To produce floating material, enclose the material you want to be
displayed separate between @code{@@float} and @code{@@end float}
commands, on lines by themselves.

Floating material often uses @code{@@image} to display an
already-existing graphic (@pxref{Images}), or @code{@@multitable} to
display a table (@pxref{Multi-column Tables}).  However, the contents
of the float can be anything.  Here's an example with simple text:

@example
@@float Figure,fig:ex1
This is an example float.
@@end float
@end example

@noindent And the output:

@float Figure,fig:ex1
This is an example float.
@end float

As shown in the example, @code{@@float} takes two arguments (separated
by a comma), @var{type} and @var{label}.  Both are optional.

@table @var
@item type
Specifies the sort of float this is; typically a word such as
``Figure'', ``Table'', etc.  If this is not given, and @var{label} is,
any cross-referencing will simply use a bare number.

@item label
Specifies a cross-reference label for this float.  If given, this
float is automatically given a number, and will appear in any
@c TODO LaTeX: figure only appears in the @listoffloats if there is a caption
@code{@@listoffloats} output (@pxref{@code{@@listoffloats}}).  Cross
references to @var{label} are allowed.  For example,
@samp{see @@ref@{fig:ex1@}} will produce see @ref{fig:ex1}.


@cindex Floats @subentry making unnumbered
@cindex Unnumbered float, creating
On the other hand, if @var{label} is not given, then the float will
not be numbered and consequently will not appear in the
@code{@@listoffloats} output or be cross-referenceable.
@end table

@noindent Ordinarily, you specify both @var{type} and @var{label}, to get a
labeled and numbered float.

In the @LaTeX{} output, code loading the @code{float} package is
output in the preamble if @code{@@float} are present.
A @code{@@float} with type @samp{figure} or @samp{table}
(case insensitive) is already defined by the package.  Other
float types lead to the definition of a new float environment,
with names based on the @code{@@float} type with anything else
than letters and @samp{-} removed.

@cindex Floats @subentry numbering of
@cindex Numbering of floats
In Texinfo, all floats are numbered in the same way: with the chapter
number (or appendix letter), a period, and the float number, which
simply counts 1, 2, 3, @dots{}, and is reset at each chapter.  Each
float type is counted independently.

Floats within an @code{@@unnumbered}, or outside of any chapter, are
simply numbered consecutively from 1.

These numbering conventions are not, at present, changeable.


@node @code{@@caption @@shortcaption}
@nodedescription Specifying descriptions for floats.
@subsection @code{@@caption} & @code{@@shortcaption}

@anchor{caption shortcaption}@c old name
@findex caption
@findex shortcaption
@cindex Captions, for floats
@cindex Short captions, for lists of floats

You may write a @code{@@caption} anywhere within a @code{@@float}
environment, to define a caption for the float.  It is not allowed in
any other context.  @code{@@caption} takes a single argument, enclosed
in braces.  Here's an example:

@example
@@float
An example float, with caption.
@@caption@{Caption for example float.@}
@@end float
@end example

@noindent The output is:

@float
An example float, with caption.
@caption{Caption for example float.}
@end float

@code{@@caption} can appear anywhere within the float; it is not
processed until the @code{@@end float}.  The caption text is usually a
sentence or two, but may consist of several paragraphs if necessary.

In the output, the caption always appears below the float; this is not
currently changeable.  It is preceded by the float type and/or number,
as specified to the @code{@@float} command (see the previous section).

The @code{@@shortcaption} command likewise may be used only within
@code{@@float}, and takes a single argument in braces.  The short
caption text is used instead of the caption text in a list of floats
(see the next section).  Thus, you can write a long caption for the
main document, and a short title to appear in the list of floats.  For
example:

@example
@@float
... as above ...
@@shortcaption@{Text for list of floats.@}
@@end float
@end example

The text for @code{@@shortcaption} may not contain comments
(@code{@@c}), verbatim text (@code{@@verb}), environments such as
@code{@@example}, footnotes (@code{@@footnote}), multiple paragraphs,
or other complex constructs.  The same constraints apply to
@code{@@caption} unless there is a @code{@@shortcaption}.  In
@LaTeX{} a multi-paragraph @code{@@caption} will lead to an error
when formatted, unless there is a @code{@@shortcaption}.


@node @code{@@listoffloats}
@nodedescription A table of contents for floats.
@subsection @code{@@listoffloats}: Tables of Contents for Floats

@anchor{listoffloats}@c old name
@findex listoffloats
@cindex List of floats
@cindex Floats @subentry list of
@cindex Table of contents, for floats

You can write a @code{@@listoffloats} command to generate a list of
floats for a given float type (@pxref{@code{@@float}}), analogous to
the document's overall table of contents.  Typically, it is written in
its own @code{@@unnumbered} node to provide a heading and structure,
rather like @code{@@printindex} (@pxref{Printing Indices & Menus}).

@code{@@listoffloats} takes one optional argument, the float type.
Here's an example:

@example
@@node List of Figures
@@unnumbered List of Figures
@@listoffloats Figure
@end example

@noindent Without any argument, @code{@@listoffloats} generates a list of
floats for which no float type was specified, i.e., no first argument to the
@code{@@float} command (@pxref{@code{@@float}}).

Here's what the output from @code{@@listoffloats}
looks like, given the example figure earlier in this chapter:

@ifinfo
@display
*      Figure 12.1:      fig:ex1.
@end display
@end ifinfo
@ifnotinfo
@listoffloats Figure
@end ifnotinfo

Usually, each line in the list of floats contains the float type (if any),
the float number, and the caption, if any---the @code{@@shortcaption}
argument, if it was specified, else the @code{@@caption} argument.
The page number may also be included, depending on output format.

Unnumbered floats (those without cross-reference labels) are omitted
from the list of floats.

The formatting of @code{@@listoffloats} depends on the output
format.  In Info, for example, a @code{@@listoffloats} is formatted
as a menu.

In @LaTeX{} output, @code{\listoffigures} is output for
the @samp{figure} (case insensitive) float type, @code{\listoftables} is output
for the @samp{table} (case insensitive) float type.  For other float types, a
specific @code{\listof} command is output.


@node Images
@nodedescription Including graphics and images.
@section Inserting Images

@cindex Images
@cindex Pictures, inserting
@findex image

You can insert an image given in an external file with the
@code{@@image} command.  Images are most often part of a displayed figure
or example, although can be used in most locations.

@node Image Syntax
@subsection Image Syntax

Here is the synopsis of the @code{@@image} command:

@example
@@image@{@var{filename}@r{[,} @var{width}@r{[,} @var{height}@r{[,} @var{alttext}@r{[, }@var{extension}@r{]]]]}@}
@end example

@cindex Formats for images
@cindex Image formats
The @var{filename} argument is mandatory, and must not have an
extension, because the different processors support different formats:

@itemize @bullet
@item
@pindex eps image format
@TeX{} (DVI output) reads the file @file{@var{filename}.eps}
(Encapsulated PostScript format).

@item
@pindex pdftex@r{, and images}
@pindex png image format
@pindex jpeg image format
@pindex pdf image inclusions
@TeX{} (PDF output) tries (in order) @file{@var{filename}.pdf}, @file{@var{filename}.png},
@file{@var{filename}.jpg}, and @file{@var{filename}.jpeg}.  It also tries uppercase versions of the extensions.  The PDF
format does not support EPS images, so such must be converted first.

@item
In Info, @file{@var{filename}.txt} is included verbatim
(more or less as if it were in @code{@@verbatim}).  The Info output
may also include a reference to @file{@var{filename}.png} or
@file{@var{filename}.jpg}.  (See below.)

@item
In HTML, a reference to @file{@var{filename}.png},
@file{@var{filename}.jpg}, @file{@var{filename}.jpeg} or
@file{@var{filename}.gif} (in that order) is output.  If
none of those exist, it gives an error, and outputs a
reference to @file{@var{filename}.jpg} anyway.

@item
@cindex SVG images, used in DocBook
In DocBook, all of the following are checked:
@file{@var{filename}.eps}, @file{@var{filename}.gif},
@file{@var{filename}.jpeg}, @file{@var{filename}.jpg},
@file{@var{filename}.pdf}, @file{@var{filename}.png} and
@file{@var{filename}.svg}.  References are output to every file found.  Also,
@file{@var{filename}.txt} is included verbatim, if present.  (The
subsequent DocBook processor is supposed to choose the appropriate one.)

@item
For @LaTeX{}, @file{@var{filename}} without any extension is used;
the subsequent @LaTeX{} processor is supposed to choose the
appropriate image type.

@item
For Info and HTML output, the optional fifth argument @var{extension}
to @code{@@image} is used for the file extension,
if it is specified and the file is found.  Any leading period should
be included in @var{extension}.  For example:

@pindex XPM image format
@example
@@image@{foo,,,,.xpm@}
@end example

@end itemize

If you want to install image files for use by Info readers too, we
recommend putting them in a subdirectory like @samp{@var{foo}-figures}
for a package @var{foo}.  Copying the files into
@code{$(infodir)/@var{foo}-figures/} should be done in your
@code{Makefile}.

The @var{width} and @var{height} arguments are described in the next
section.

@cindex Images @subentry using inside paragraphs
We recommend you try to avoid using images inside paragraphs.  The
results will likely be sub-optimal in Info format, as @command{texi2any}
does not have enough information to break lines around the image in the
best place.  (The results are likely to be especially bad if
@file{@var{filename}.txt} consists of more than one line of text.)

If an image is the first thing in a paragraph and followed by
more text, then you should precede the @code{@@image} command with
@code{@@indent} or @code{@@noindent} to indicate the beginning of
paragraph formatting.  This is especially important for @TeX{} output
to get correct paragraph indentation.

Use @code{@@center} to center an image
(@pxref{@code{@@titlefont @@center @@sp}}).

@cindex Alt attribute for images
@cindex Images @subentry alternate text for
@cindex @sortas{-} -@r{ (in image alt string)}
For HTML output, the @dfn{alt attribute} for
inline images is set to the optional @var{alttext} (fourth) argument to
@code{@@image}, if supplied.  If not supplied, the full file name of
the image being displayed is used.  The @var{alttext} is
processed as Texinfo text, so special characters such as @samp{"} and
@samp{<} and @samp{&} are escaped in the HTML output; also, you can
get an empty @code{alt} string with @code{@@-} (a command that
produces no output; @pxref{@code{@@- @@hyphenation}}).

For Info output, the @var{alttext} string is also processed as Texinfo
text and output.  In this case, @samp{\} is escaped as @samp{\\} and
@samp{"} as @samp{\"}; no other escapes are done.

In Info output, a reference to the binary image file is written
(trying @var{filename} suffixed with @file{@var{extension}},
@file{@var{.extension}}, @file{.png}, or @file{.jpg}, in that order)
if one exists.  The @file{.txt} file is also literally included, if one
exists.  This way, Info readers which can display images (such as the
Emacs Info browser, running under X) can do so, whereas Info readers
which can only use text (such as the standalone Info reader) can
display the textual version.

@c Texinfo version 4.6 was released in 2003
@ignore
@cindex @samp{^@@^H} for images in Info
The implementation of this is to put the following construct into the
Info output:

@example
^@@^H[image src="@var{binaryfile}" text="@var{txtfile}"
           alt="@var{alttext} ... ^@@^H]
@end example

@noindent where @samp{^@@} and @samp{^H} stand for the actual null and
backspace control characters.  If one of the files is not present, the
corresponding argument is omitted.

The reason for mentioning this here is that older Info browsers (this
feature was introduced in Texinfo version 4.6) will display the above
literally, which, although not pretty, should not be harmful.
@end ignore


@node Image Scaling
@subsection Image Scaling

@cindex Images @subentry scaling
@cindex Scaling images
@cindex Width of images
@cindex Height of images
@cindex Aspect ratio of images
@cindex Distorting images
The optional @var{width} and @var{height} arguments to the
@code{@@image} command (see the previous section) specify the size to
which to scale the image.  They are only taken into account in printed
output.

In @TeX{}, if neither is specified, the image is presented in its natural size
(given in the file); if only one is specified, the other is scaled
proportionately; and if both are specified, both are respected, thus likely
distorting the original image by changing its aspect ratio.

@cindex Dimensions and image sizes
The @var{width} and @var{height} may be specified using any valid @TeX{}
dimension, namely:

@table @asis
@item pt
@cindex Points (dimension)
point (72.27pt = 1in)
@item pc
@cindex Picas
pica (1pc = 12pt)
@item bp
@cindex Big points
big point (72bp = 1in)
@item in
@cindex Inches
inch
@item cm
@cindex Centimeters
centimeter (2.54cm = 1in)
@item mm
@cindex Millimeters
millimeter (10mm = 1cm)
@item dd
@cindex Did@^ot points
did@^ot point (1157dd = 1238pt)
@item cc
@cindex Ciceros
cicero (1cc = 12dd)
@item sp
@cindex Scaled points
scaled point (65536sp = 1pt)
@end table

@pindex ridt.eps
For example, the following will scale a file @file{ridt.eps} to one
inch vertically, with the width scaled proportionately:

@example
@@image@{ridt,,1in@}
@end example

@pindex epsf.tex
For @code{@@image} to work with @TeX{}, the file @file{epsf.tex} must be
installed somewhere that @TeX{} can find it.  (The standard location is
@file{@var{texmf}/tex/generic/dvips/epsf.tex}, where @var{texmf} is a
root of your @TeX{} directory tree.)  This file is included in the
Texinfo distribution and is also available from
@uref{ftp://tug.org/tex/epsf.tex}, among other places.

@code{@@image} can be used within a line as well as for displayed
figures.  Therefore, if you intend it to be displayed, be sure to leave
a blank line before the command, or the output will run into the
preceding text.

Image scaling is presently implemented only in printed output, not in
any other sort of output.


@node Footnotes
@nodedescription Writing footnotes.
@section Footnotes
@cindex Footnotes
@findex footnote

A @dfn{footnote} is for a reference that documents or elucidates the
primary text.@footnote{A footnote should complement or expand upon the
primary text, but a reader should not need to read a footnote to
understand the primary text.  For a thorough discussion of footnotes,
see @cite{The Chicago Manual of Style}, which is published by the
University of Chicago Press.}

Footnotes are distracting; use them sparingly at most, and it is best
to avoid them completely.  Standard bibliographical references are
usually better placed in a bibliography at the end of a document
instead of in footnotes throughout.


@node Footnote Commands
@nodedescription How to write a footnote in Texinfo.
@subsection Footnote Commands

In Texinfo, footnotes are created with the @code{@@footnote} command.
This command is followed immediately by a left brace, then by the text
of the footnote, and then by a terminating right brace.  Footnotes may
be of any length (they will be broken across pages if necessary), but
are usually short.  The template is:

@example
ordinary text@@footnote@{@var{text of footnote}@}
@end example

As shown here, the @code{@@footnote} command should come right after the
text being footnoted, with no intervening space; otherwise, the footnote
marker might end up starting a line.

For example, this clause is followed by a sample footnote@footnote{Here
is the sample footnote.}; in the Texinfo source, it looks like
this:

@example
@dots{}a sample footnote@@footnote@{Here is the sample
footnote.@}; in the Texinfo source@dots{}
@end example

As you can see, this source includes two punctuation marks next to
each other; in this case, @samp{.@};} is the sequence.  This is normal
(the first ends the footnote and the second belongs to the sentence
being footnoted), so don't worry that it looks odd.  (Another style,
perfectly acceptable, is to put the footnote after punctuation
belonging to the sentence, as in @samp{;@@footnote@{...}.)

In printed output formats, the reference mark for a footnote is a
small, superscripted number; the text of the footnote appears at the
bottom of the page, below a horizontal line.

In Info, the reference mark for a footnote is a pair of parentheses
with the footnote number between them, like this: @samp{(1)}.  The
reference mark is followed by a cross-reference link to the footnote
text if footnotes are put in separate nodes (@pxref{Footnote Styles}).

In the HTML output, footnote references are generally marked with a
small, superscripted number which is rendered as a hypertext link to
the footnote text.

@cindex Critical editions
@cindex Nested footnotes
Footnotes cannot be nested, and cannot appear in section headings of
any kind or other ``unusual'' places.

A final tip: footnotes in the argument of an @code{@@item} command for
an @code{@@table} must be entirely on the same line as the
@code{@@item} (as usual).  @xref{Two-column Tables}.


@node Footnote Styles
@nodedescription Controlling how footnotes appear.
@subsection Footnote Styles

Online formats have two footnote styles, which determine where
the text of the footnote is located, the @samp{end} and @samp{separate}
footnote style.

@table @samp
@cindex @samp{end} node footnote style
@cindex Footnote style @subentry @samp{end}
@item end
For Info, in the @samp{end} node style, all the footnotes for a single
node are placed at the end of that node.  The footnotes are separated
from the rest of the node by a line of dashes with the word
@samp{Footnotes} within it.  Each footnote begins with an
@samp{(@var{n})} reference mark.

@need 700
@noindent
Here is an example of the Info output for a single footnote in the
end-of-node style:

@example
@group
--------- Footnotes ---------

(1)  Here is a sample footnote.
@end group
@end example

In HTML, when the footnote style is @samp{end}, or if the output is
not split, footnotes are put at the end of each output file.

@cindex @samp{separate} footnote style
@cindex Footnote style @subentry @samp{separate}
@item separate
For Info, in the @samp{separate} node style, all the footnotes
for a single node are placed in an automatically constructed
node of their own.  In this style, a ``footnote reference'' follows
each @samp{(@var{n})} reference mark in the body of the
node.  The footnote reference is actually a cross-reference
which you use to reach the footnote node.

The name of the node with the footnotes is constructed
by appending @w{@samp{-Footnotes}} to the name of the node
that contains the footnotes. (Consequently, the footnotes'
node for the @file{Footnotes} node is
@w{@file{Footnotes-Footnotes}}!)  The footnotes' node has an
`Up' node pointer that leads back to its parent node.

@noindent
Here is how the first footnote in this manual looks after being
formatted for Info in the separate node style:

@example
@group
File: texinfo.info  Node: Overview-Footnotes, Up: Overview

(1) The first syllable of "Texinfo" is pronounced like
"speck", not "hex". @dots{}
@end group
@end example

In HTML, when the footnote style is @samp{separate}, and the output
is split, footnotes are placed in a separate file.
@end table

Unless your document has long and important footnotes (as in, say,
Gibbon's @cite{Decline and Fall @dots{}}), we recommend the @samp{end}
style, as it is simpler for readers to follow.

@findex footnotestyle
Use the @code{@@footnotestyle} command to specify the
footnote style.  Write this command at the beginning of a line followed
by an argument, either @samp{end} for the end node style or
@samp{separate} for the separate node style.

@need 700
For example,

@example
@@footnotestyle end
@end example
@noindent
or
@example
@@footnotestyle separate
@end example

Write a @code{@@footnotestyle} command in the Texinfo file preamble.


@node Indices
@nodedescription Creating indices.
@chapter Indices
@cindex Indices

Using Texinfo, you can generate indices without having to sort and
collate entries manually.  In an index, the entries are listed in
alphabetical order, together with information on how to find the
discussion of each entry.  In a printed manual, this information
consists of page numbers.  In other formats, links to the index
entries location or to the associated nodes are generated.

Texinfo provides several predefined kinds of indices: an index for
functions, an index for variables, an index for concepts, and so on.
You can combine indices or use them for other than their canonical
purpose.  Lastly, you can define your own new indices.


@node Predefined Indices
@nodedescription Use different indices for different kinds of entries.
@section Predefined Indices

Texinfo provides six predefined indices.  Here are their nominal
meanings, abbreviations, and the corresponding index entry commands:

@table @samp
@item cp
@cindex @code{cp} (concept) index
@findex cindex
@findex cpindex
(@code{@@cindex}) Concept index, for general concepts.
@item fn
@cindex @code{fn} (function) index
@findex findex
@findex fnindex
(@code{@@findex}) Function index, for function and function-like
names (such as entry points of libraries).
@item ky
@cindex @code{ky} (keystroke) index
@findex kindex
@findex kyindex
(@code{@@kindex}) Keystroke index, for keyboard commands.
@item pg
@cindex @code{pg} (program) index
@findex pindex
@findex pgindex
(@code{@@pindex}) Program index, for names of programs.
@item tp
@cindex @code{tp} (data type) index
@findex tindex
@findex tpindex
(@code{@@tindex}) Data type index, for type names (such as structures
defined in header files).
@item vr
@cindex @code{vr} (variable) index
@findex vindex
@findex vrindex
(@code{@@vindex}) Variable index, for variable names (such as library global
variables).
@end table

@noindent
Not every manual needs all of these, and most manuals use only two or
three at most.  The present manual, for example, has three indices: a
concept index, a variable index, and an @@-command index.  (The last is
actually the function index but is called a command index in the chapter
heading.)

You are not required to use the predefined indices strictly for their
canonical purposes.  For example, suppose you wish to index some C
preprocessor macros.  You could put them in the function index along
with actual functions, just by writing @code{@@findex} commands for
them; then, when you print the ``Function Index'' as an unnumbered
chapter, you could give it the title `Function and Macro Index' and
all will be consistent for the reader.

On the other hand, it is best not to stray too far from the meaning of
the predefined indices.  Otherwise, in the event that your text is
combined with other text from other manuals, the index entries will
not match up.  Instead, define your own new index (@pxref{New
Indices}).

We recommend having a single index in the final document whenever
possible, however many source indices you use, since then readers have
only one place to look.  Two or more source indices can be combined
into one output index by using the @code{@@synindex} or
@code{@@syncodeindex} commands (@pxref{Combining Indices}).

Index entry commands based on the two letter index names are also
valid, for example @code{@@cpindex} can be used instead of @code{@@cindex}.


@node Indexing Commands
@nodedescription How to make an index entry.
@section Defining the Entries of an Index

@cindex Defining indexing entries
@cindex Index entries
@cindex Entries for an index
@cindex Specifying index entries
@cindex Creating index entries

The data to make an index come from many individual indexing commands
scattered throughout the Texinfo source file.  Each command says to add
one entry to a particular index; after formatting, the index will give
the current page number or node name as the reference.

An index entry consists of an indexing command at the beginning of a
line followed, on the rest of the line, by the entry.

For example, this section begins with the following five entries for
the concept index:

@example
@@cindex Defining indexing entries
@@cindex Index entries, defining
@@cindex Entries for an index
@@cindex Specifying index entries
@@cindex Creating index entries
@end example

Each predefined index has its own indexing command---@code{@@cindex}
for the concept index, @code{@@findex} for the function index, and so
on, as listed in the previous section.

Index entries should precede the visible material that is being
indexed.  For instance:

@example
@@cindex hello
Hello, there!
@end example

@noindent Among other reasons, that way following indexing links (in
whatever context) ends up before the material, where readers want to
be, instead of after.

In Info, an index is usually formatted as a menu.  Try to avoid using
a colon in index entries, as this may confuse some Info readers.
@xref{Menu Parts} for more information about the structure of a menu entry.
@c At the time of writing, it always works in standalone info, and a
@c single colon not followed by a space works in Emacs.

@cindex Index font types
By default, entries for a concept index are printed in a roman
font and entries for the other indices are printed in a typewriter font.
You may change the way part of an entry is printed with the usual
Texinfo commands, such as @code{@@file} for
file names (@pxref{Marking Text}), and @code{@@r} for the normal roman
font (@pxref{Fonts}).

@findex sortas
@cindex sort keys for index entries
@cindex index sorting
You may specify an explicit sort key for an
index entry using @code{@@sortas} following either the index command
or the text of the entry.  For example: @samp{@@findex @@sortas@{\@}
\ @@r@{(literal \ in @@code@{@@@@math@})} sorts the index entry this
produces under backslash.

@vindex txiindexbackslashignore
@vindex txiindexhyphenignore
@vindex txiindexlessthanignore
@vindex txiindexatsignignore
You may choose to ignore certain characters in index entries
for the purposes of sorting.  The characters that you can
currently choose to ignore are @samp{\}, @samp{-}, @samp{<}
and @samp{@@}, which are ignored by giving as an argument to the
@code{@@set} command, respectively, @code{txiindexbackslashignore},
@code{txiindexhyphenignore}, @code{txiindexlessthanignore} and
@code{txiindexatsignignore}.  For example, specifying @samp{@@set
txiindexbackslashignore} causes the @samp{\mathopsup} entry in the
index for this manual to be sorted as if it were @samp{mathopsup},
so that it appears among the other entries beginning with `M'.
This avoids the need to provide explicit sort keys for index
entries containing these characters.

When using these options, it is possible to get an index entry with
an empty sort key.  To avoid this, specify a @code{@@sortas} directive
in the index entry.  For example:

@example
@@set txiindexbackslashignore
@@findex @@sortas@{\@} \
@end example


@node Advanced Indexing
@nodedescription Advanced indexing commands.
@section Advanced Indexing Commands
@cindex Indexing, advanced
@cindex Advanced indexing

Texinfo provides several further commands for indexing.

@findex subentry
First, you can create @dfn{multilevel} index entries, allowing you
to group many related subtopics under the same higher-level topic.
You do this by separating the parts of such an entry with the
@code{@@subentry} command. Such commands might look like this:

@example
@@cindex Superhumans @@subentry villains
@@cindex Superhumans @@subentry heroes
@end example

You may have up to three levels in an entry:

@example
@@cindex coffee makers @@subentry electric @@subentry pink
@@cindex coffee makers @@subentry electric @@subentry blue
@end example

You can use the @code{@@sortas} command mentioned earlier with any or
all of the three parts of an entry to cause them to sort differently
than they would by default.

@findex seeentry
Second, you may provide an index entry that points to another,
using the @code{@@seeentry} (``see entry'') command. For example:

@example
@@cindex Indexes @@seeentry@{Indices@}
@end example

Such an entry should be unique in your document; the idea is to
redirect the reader to the other entry where they will find all
the information they are looking for.

@findex seealso
Finally, you may provide a ``see also'' entry using the @code{@@seealso}
command. These entries go along with regular entries, and are grouped
together with them in the final printed index. For example:

@example
@@cindex Coffee
@@cindex Coffee @@subentry With milk and sugar
@@cindex Coffee @@subentry With doughnuts
@@cindex Coffee @@subentry Decaffeinated
@@cindex Coffee @@seealso@{Tea@}
@end example

When using all three of these advanced commands, @emph{do not}
place a comma between the different parts of the index text. The
@command{texindex} program, which sorts the index entries and
generates the indexing formatting commands, takes care of placing
commas in the correct places for you.

Do not interrupt an index or @code{@@subentry} entry by @code{@@sortas}
or advanced commands with braces; place the commands with braces at
the beginning or at the end of the entry.

These features are the most useful with printed documents, and
when translating Texinfo to DocBook.


@node Index Entries
@nodedescription Choose different words for index entries.
@section Making Index Entries
@cindex Index entries, making
@cindex Entries, making index

@cindex Writing index entries
@cindex Index entries, advice on writing
@cindex Advice on writing entries
@cindex Capitalization of index entries
Concept index entries consist of text.  The best way to write an index
is to devise entries which are terse yet clear.  If you can do this,
the index usually looks better if the entries are written just as they
would appear in the middle of a sentence, that is, capitalizing only
proper names and acronyms that always call for uppercase letters.
This is the case convention we use in most GNU manuals' indices.

If you don't see how to make an entry terse yet clear, make it longer
and clear---not terse and confusing.  If many of the entries are
several words long, the index may look better if you use a different
convention: capitalize the first word of each entry.  Whichever
case convention you use, use it consistently.

In any event, do not ever capitalize a case-sensitive name such as a C
or Lisp function name or a shell command; that would be a spelling
error.  Entries in indices other than the concept index are symbol
names in programming languages, or program names; these names are
usually case-sensitive, so likewise use upper- and lowercase as
required.

@cindex Unique index entries
It is a good idea to make index entries unique wherever feasible.
That way, people using the printed output or online completion of
index entries don't see undifferentiated lists.  Consider this an
opportunity to make otherwise-identical index entries be more
specific, so readers can more easily find the exact place they are
looking for.
The advanced indexing features described in @ref{Advanced Indexing}
can help with this, as well.


When you are making index entries, it is good practice to think of the
different ways people may look for something.  Different people
@emph{do not} think of the same words when they look something up.  A
helpful index will have items indexed under all the different words
that people may use.  For example, one reader may think it obvious
that the two-letter names for indices should be listed under
``Indices, two-letter names'', since ``Indices'' are the general
concept.  But another reader may remember the specific concept of
two-letter names and search for the entry listed as ``Two letter names
for indices''.  A good index will have both entries and will help both
readers.

Like typesetting, the construction of an index is a skilled art, the
subtleties of which may not be appreciated until you need to do it
yourself.


@node Printing Indices & Menus
@nodedescription How to print an index in hardcopy and generate index menus in Info.
@section Printing Indices and Menus
@cindex Printing an index
@cindex Indices, printing and menus
@cindex Generating menus with indices
@cindex Menus generated with indices


@findex printindex
@code{@@printindex} takes one argument, a two-letter index
abbreviation.  You must include the @code{@@printindex} command at the
place in the document where you want the index to appear.  This does
not happen automatically just because you use @code{@@cindex} or other
index-entry generating commands in the Texinfo file; those just cause
the raw data for the index to be accumulated.

You should precede the @code{@@printindex} command with
a suitable section or chapter command (usually @code{@@appendix} or
@code{@@unnumbered}) to supply the chapter heading and put the index
into the table of contents.  Precede the chapter heading with an
@code{@@node} line as usual.

For example:

@example
@group
@@node Variable Index
@@unnumbered Variable Index

@@printindex vr
@end group

@group
@@node Concept Index
@@unnumbered Concept Index

@@printindex cp
@end group
@end example

The text @samp{Index} needs to appear in the name of the node containing the
index for the index to be found by Info readers.

If you have more than one index, we recommend placing the concept index last.

Other details of index output in output formats:

@itemize
@item
As part of the process of creating a printed manual with @TeX{},
you run a program called @command{texindex} (@pxref{Hardcopy with @TeX{}})
to sort the raw data to produce a sorted index file.  The sorted index
file is what is actually used to print the index.

@code{@@printindex} reads the corresponding sorted index file and produces
a traditional two-column index, with index terms and page numbers.

@item
In Info output, @code{@@printindex} produces a special menu containing
the line number of the entry, relative to the start of the node.  Info
readers can use this to go to the exact line of an entry, not just the
containing node.  (Older Info readers will just go to the node.)
Here's an example:

@example
* First index entry:   Top.   (line  7)
@end example

@item
In plain text output, @code{@@printindex} formatting is usually similar to a
menu in Info, showing the line number of each entry relative to the start of
the file.

@item
In HTML output, @code{@@printindex} produces links to the index
entries.

@item
In DocBook and @LaTeX{} output, it simply records the index to be printed.
@end itemize


@node Combining Indices
@nodedescription How to combine indices.
@section Combining Indices
@cindex Combining indices
@cindex Indices, combining them

Sometimes you will want to combine two disparate indices such as
functions and concepts, perhaps because you have few enough entries
that a separate index would look silly.

You could put functions into the concept index by writing
@code{@@cindex} commands for them instead of @code{@@findex} commands,
and produce a consistent manual by printing the concept index with the
title `Function and Concept Index' and not printing the `Function
Index' at all; but this is not a robust procedure.  It works only if
your document is never included as part of another document that is
designed to have a separate function index; if your document were to
be included with such a document, the functions from your document and
those from the other would not end up together.  Also, to make your
function names appear in the right font in the concept index, you
would need to enclose every one of them between the braces of
@code{@@code}.


@node @code{@@syncodeindex}
@nodedescription How to merge two indices, using @code{@@code} font for the merged-from index.
@subsection @code{@@syncodeindex}: Combining Indices Using @code{@@code}

@anchor{syncodeindex}@c old name
@findex syncodeindex

When you want to combine functions and concepts into one index, you
should index the functions with @code{@@findex} and index the concepts
with @code{@@cindex}, and use the @code{@@syncodeindex} command to
redirect the function index entries into the concept index.

The @code{@@syncodeindex} command takes two arguments; they are the name
of the index to redirect, and the name of the index to redirect it to.
The template looks like this:

@example
@@syncodeindex @var{from} @var{to}
@end example

@cindex Predefined names for indices
@cindex Two letter names for indices
@cindex Indices, two letter names
@cindex Names for indices
For this purpose, the indices are given two-letter names:

@table @samp
@item cp
Concept index
@item fn
Function index
@item ky
Key index
@item pg
Program index
@item tp
Data type index
@item vr
Variable index
@end table

Write a @code{@@syncodeindex} command before or shortly after the
end-of-header line at the beginning of a Texinfo file.  For example,
to merge a function index with a concept index, write the
following:

@example
@@syncodeindex fn cp
@end example

@noindent
This causes all entries designated for the function index to merge
in with the concept index instead.

To merge both a variable index and a function index into a concept
index, write the following:

@example
@group
@@syncodeindex vr cp
@@syncodeindex fn cp
@end group
@end example

@cindex Fonts for indices
The @code{@@syncodeindex} command puts all the entries from the `from'
index (the redirected index) into the @code{@@code} font, overriding
whatever default font is used by the index to which the entries are
now directed.  This way, if you direct function names from a function
index into a concept index, all the function names are printed in the
@code{@@code} font as you would expect.


@node @code{@@synindex}
@nodedescription How to merge two indices, using the roman font for the merged-from index.
@subsection @code{@@synindex}: Combining Indices

@anchor{synindex}@c old name
@findex synindex

The @code{@@synindex} command is nearly the same as the
@code{@@syncodeindex} command, except that it does not put the `from'
index entries into the @code{@@code} font; rather it puts them in the
roman font.  Thus, you use @code{@@synindex} when you merge a concept
index into a function index.

@xref{Printing Indices & Menus}, for information about printing an index
at the end of a book or creating an index menu in an Info file.


@node New Indices
@nodedescription How to define your own indices.
@section Defining New Indices

@cindex Defining new indices
@cindex Indices, defining new
@cindex New index defining
@findex defindex
@findex defcodeindex

In addition to the predefined indices (@pxref{Predefined Indices}),
you may use the @code{@@defindex} and @code{@@defcodeindex} commands
to define new indices.  These commands create new indexing @@-commands
with which you mark index entries.  The @code{@@defindex} command is
used like this:

@example
@@defindex @var{name}
@end example

New index names are usually two-letter words, such as @samp{au}.
For example:

@example
@@defindex au
@end example

This defines a new index, called the @samp{au} index.  At the same
time, it creates a new indexing command, @code{@@auindex}, that you
can use to make index entries.  Use this new indexing command just as
you would use a predefined indexing command.

For example, here is a section heading followed by a concept index
entry and two @samp{au} index entries.

@example
@@section Cognitive Semantics
@@cindex kinesthetic image schemas
@@auindex Johnson, Mark
@@auindex Lakoff, George
@end example

@noindent
(Evidently, @samp{au} serves here as an abbreviation for ``author''.)

Texinfo constructs the new indexing command by concatenating the name
of the index with @samp{index}; thus, defining an @samp{xy} index
leads to the automatic creation of an @code{@@xyindex} command.

Use the @code{@@printindex} command to print the index, as you do with
the predefined indices.  For example:

@example
@group
@@node Author Index
@@unnumbered Author Index

@@printindex au
@end group
@end example

The @code{@@defcodeindex} command is like the @code{@@defindex} command,
except that, in the printed output, it prints entries in an
@code{@@code} font by default instead of in a roman font.

You should define new indices before the end-of-header line of a
Texinfo file, and (of course) before any @code{@@synindex} or
@code{@@syncodeindex} commands (@pxref{Texinfo File Header}).

As mentioned earlier (@pxref{Predefined Indices}), we recommend having
a single index in the final document whenever possible (no matter how many
source indices you use), since then readers have only one place to
look.

When creating an index, @TeX{} creates a file whose extension is the
name of the index (@pxref{Names of index files}).  Therefore you
should avoid using index names that collide with extensions used for
other purposes, such as @samp{.aux} or @samp{.xml}.
@command{texi2any} already reports an error if a new index conflicts
well-known extension name.


@node Insertions
@nodedescription Inserting @@-signs, braces, etc.
@chapter Special Insertions
@cindex Inserting special characters and symbols
@cindex Special insertions

Texinfo provides several commands for inserting characters that have
special meaning in Texinfo, such as braces, and for other graphic
elements that do not correspond to simple characters you can type.


@node Special Characters
@nodedescription Inserting @@ @{@} , \ # &
@section Special Characters: Inserting @@ @{@} , \ # &
@anchor{Braces Atsign}@c previous names for this node
@anchor{Atsign Braces Comma}
@cindex Special characters, inserting
@cindex Commands to insert special characters

@samp{@@} and curly braces are the basic special characters in
Texinfo.  To insert these characters so they appear in text, you must
put an @samp{@@} in front of these characters to prevent Texinfo from
misinterpreting them.  Alphabetic commands are also provided.

The other characters (comma, backslash, hash, ampersand) are special 
only in restricted contexts, as explained in the respective sections.


@node Inserting an Atsign
@nodedescription @code{@@@@}, @code{@@atchar@{@}}.
@subsection Inserting `@@' with @code{@@@@} and @code{@@atchar@{@}}
@cindex At sign, inserting
@cindex Inserting @@ @r{(literal @samp{@@})}
@findex @sortas{@@} @@ @r{(literal @samp{@@})}
@ifset commandlookup
@findex @sortas{@@} @@
@end ifset
@findex atchar

@code{@@@@} produces a single @samp{@@} character in the output.  Do
not put braces after an @code{@@@@} command.

@code{@@atchar@{@}} also produces a single @samp{@@} character in the
output.  It does need following braces, as usual for alphabetic
commands.  In inline conditionals (@pxref{Inline Conditionals}), it
can be necessary to avoid using the literal @samp{@@} character in the
source (and may be clearer in other contexts).


@node Inserting Braces
@nodedescription @code{@@@{ @@@}}, @code{@@l rbracechar@{@}}.
@subsection Inserting `@{ `@}' with @code{@@@{ @@@}} and @code{@@l rbracechar@{@}}

@findex @{ @r{(literal @samp{@{})}
@findex @} @r{(literal @samp{@}})}
@ifset commandlookup
@findex @{
@findex @}
@end ifset
@findex lbracechar
@findex rbracechar
@cindex Braces, inserting

@code{@@@{} produces a single @samp{@{} in the output, and @code{@@@}}
produces a single @samp{@}}.  Do not put braces after either an
@code{@@@{} or an @code{@@@}} command.

@code{@@lbracechar@{@}} and @code{@@rbracechar@{@}} also produce
single @samp{@{} and @samp{@}} characters in the output.  They do need
following braces, as usual for alphabetic commands.  In inline
conditionals (@pxref{Inline Conditionals}), it can be
necessary to avoid using literal brace characters in the source (and
may be clearer in other contexts).


@node Inserting a Comma
@nodedescription , and @code{@@comma@{@}}.
@subsection Inserting `,' with @code{@@comma@{@}}

@findex comma
@cindex Comma, inserting

Ordinarily, a comma `,' is a normal character that can be simply typed
in your input where you need it.

However, Texinfo uses the comma as a special character only in one
context: to separate arguments to those Texinfo commands, such as
@code{@@node} (@pxref{Node Line Requirements}),
@code{@@acronym} (@pxref{@code{@@acronym}}) and @code{@@xref}
(@pxref{Cross References}), as well as user-defined macros
(@pxref{Defining Macros}), which take more than one argument.

Since a comma character would confuse Texinfo's parsing for these
commands, you must use the command @samp{@@comma@{@}} instead if you want
to pass an actual comma.  Here are some examples:

@example
@@acronym@{ABC, A Bizarre @@comma@{@}@}
@@xref@{Comma,, The @@comma@{@} symbol@}
@@mymac@{One argument@@comma@{@} containing a comma@}
@end example

Although @samp{@@comma@{@}} can be used nearly anywhere, there is no
need for it anywhere except in this unusual case.

(Incidentally, the name @samp{@@comma} lacks the @samp{char} suffix used
in its companion commands only for historical reasons.  It didn't seem
important enough to define a synonym.)


@node Inserting a Backslash
@nodedescription \ and @code{@@backslashchar@{@}}.
@subsection Inserting `\' with @code{@@backslashchar@{@}}

@findex backslashchar
@cindex Backslash, inserting

Ordinarily, a backslash `\' is a normal character in Texinfo that can
be simply typed in your input where you need it.  The result is to
typeset the backslash from the typewriter font.

However, Texinfo uses the backslash as a special character in one
restricted context: to delimit formal arguments in the bodies of
user-defined macros (@pxref{Defining Macros}).

Due to the vagaries of macro argument parsing, it is more reliable to
pass an alphabetic command that produces a backslash instead of using
a literal \.  Hence @code{@@backslashchar@{@}}.  Here is an example
macro call:

@example
@@mymac@{One argument@@backslashchar@{@} with a backslash@}
@end example

@findex \backslash
@findex @sortas{\} \ @r{(literal @samp{\} in math)}
@ifset commandlookup
@findex @sortas{\} \
@end ifset
Texinfo documents may also use \ as a command character inside
@code{@@math} (@pxref{Inserting Math}).  In this case, @code{@@\} or
@code{\backslash} produce a ``math'' backslash (from the math symbol
font), while @code{@@backslashchar@{@}} produces a typewriter
backslash as usual.

Although @samp{@@backslashchar@{@}} can be used nearly anywhere, there
is no need for it except in these unusual cases.


@node Inserting a Hashsign
@nodedescription # and @code{@@hashchar@{@}}.
@subsection Inserting `#' with @code{@@hashchar@{@}}

@findex hashchar
@cindex Inserting #
@cindex Hash sign, inserting

Ordinarily, a hash `#' is a normal character in Texinfo that can be
simply typed in your input where you need it.  The result is to
typeset the hash character from the current font.

@cindex Number sign, inserting
@cindex Octothorp, inserting
@cindex Sharp sign (not), inserting
This character has many other names, varying by locale, such as
``number sign'', ``pound'', and ``octothorp''.  It is also sometimes
called ``sharp'' or ``sharp sign'' since it vaguely resembles the
musical symbol by that name.  In situations where Texinfo is used,
``hash'' is the most common in our experience.

However, Texinfo uses the hash character as a special character in one
restricted context: to introduce the so-called @code{#line} directive
and variants (@pxref{External Macro Processors}).

So, in order to typeset an actual hash character in such a place (for
example, in a program that needs documentation about @code{#line}),
it's necessary to use @code{@@hashchar@{@}} or some other construct.
Here's an example:

@example
@@hashchar@{@} 10 "example.c"
@end example

Although @samp{@@hashchar@{@}} can be used nearly anywhere, there
is no need for it anywhere except this unusual case.


@node Inserting an Ampersand
@nodedescription & and @code{@@ampchar@{@}}.
@subsection Inserting `&' with @code{@@&} and @code{@@ampchar@{@}}

@findex ampchar
@findex & @r{(literal @samp{&})}
@ifset commandlookup
@findex &
@end ifset
@cindex Inserting &
@cindex Ampersand, inserting

Ordinarily, an ampersand `&' is a normal character in Texinfo that can be
simply typed in your input where you need it.  The result is to
typeset the ampersand character.

However, the ampersand character is treated specially in just
one restricted context.   In the argument to a definition command
(@pxref{Definition Commands}), an ampersand followed by a series
of letters may be typeset specially when processing with
@TeX{}@footnote{This syntax is used for Emacs Lisp keywords. @xref{A
Sample Function Description,,, elisp, GNU Emacs Lisp Reference
Manual}.} (@pxref{Def Cmd Conventions}).  For example:

@example
@@defun foo integer1 &optional integer2 &rest integers
@@code@{foo@} described here.
@@end defun
@end example

@noindent may have @samp{&optional} and @samp{&rest} formatted in bold,
even without any @@-command involved.

So, in order to typeset an ampersand in such a context,
it's necessary to use @code{@@&} or some other construct.
Here's an example of a C++ function taking a reference as a parameter:

@example
@@deftypefn Function int foo (const std::vector<int>@@& @@var@{bar@})
Documentation of @@code@{foo@}.
@@end deftypefn
@end example

@noindent This gives the output 

@deftypefn Function int foo (const std::vector<int>@& @var{bar})
Documentation of @code{foo}.
@end deftypefn

Although @samp{@@&} and @samp{@@ampchar@{@}} can be used nearly 
anywhere, there is no need for them anywhere except this unusual case.


@node Inserting Quote Characters
@nodedescription Inserting left and right quotes, in code.
@section Inserting Quote Characters

@cindex Inserting quote characters
@cindex Quote characters, inserting

As explained in the early section on general Texinfo input conventions
(@pxref{Conventions}), Texinfo source files use the ASCII character
@code{`} (96 decimal) to produce a left quote (`), and ASCII @code{'}
(39 decimal) to produce a right quote (').  Doubling these input
characters (@code{``} and @code{''}) produces double quotes (`` and
'').  These are the conventions used by @TeX{}.

In examples of computer code, however, @code{`} and @code{'} produce
typical renderings for these ASCII characters: the backtick character
(standalone grave accent) and undirected single quote respectively.
In the past, directed glyphs
@iftex
@clear txicodequoteundirected
@clear txicodequotebacktick
(@code{`} and @code{'})
@set txicodequoteundirected
@set txicodequotebacktick
@end iftex
were used by default in @TeX{} output.  Texinfo provides these commands
to choose between these alternate renderings:

@table @code
@findex codequoteundirected
@cindex undirected single quote
@item @@codequoteundirected @var{on-off}
Set to @samp{off} to output the @code{'} character in code environments
as the right curly single quote.

@findex codequotebacktick
@cindex Backtick
@cindex Grave accent @subentry standalone
@item @@codequotebacktick @var{on-off}
Set to @samp{off} to output the @code{`} character in code environments
as the left curly single quote.
@end table

If you want these settings for only part of the document,
@code{@@codequote... on} will restore the normal behavior, as in
@code{@@codequoteundirected on}.

These settings affect @code{@@code}, @code{@@example}, @code{@@kbd},
@code{@@samp}, @code{@@verb}, and @code{@@verbatim}.  @xref{Useful
Highlighting}.

Unfortunately, some document viewers will mangle the directed
quote characters when copying and pasting.  (The free PDF reader
@command{xpdf} works fine, but other PDF readers, both free and
nonfree, have problems.)

@vindex txicodequoteundirected
@vindex txicodequotebacktick
This feature can also be controlled by using @code{@@set}
and @code{@@clear} on the corresponding variables
@code{txicodequoteundirected} and @code{txicodequotebacktick}.


@node Inserting Space
@nodedescription Inserting the right amount of whitespace.
@section Inserting Space

@cindex Inserting space
@cindex Spacing, inserting
The following sections describe commands that control spacing of various
kinds within and after sentences.


@node Multiple Spaces
@nodedescription Inserting multiple spaces.
@subsection Multiple Spaces

@cindex Multiple spaces
@cindex Whitespace, inserting
@cindex Space, inserting horizontal
@findex <space>
@findex <tab>
@findex <newline>

Ordinarily, multiple whitespace characters (space, tab, and newline)
are collapsed into a single space.

Occasionally, you may want to produce several consecutive spaces,
either for purposes of example (e.g., what your program does with
multiple spaces as input), or merely for purposes of appearance in
headings or lists.  Texinfo supports three commands:
@code{@@@kbd{SPACE}}, @code{@@@kbd{TAB}}, and @code{@@@kbd{NL}}, all
of which insert a single space into the output.  (Here,
@code{@@@kbd{SPACE}} represents an @samp{@@} character followed by a
space, i.e., @samp{@@ }, @kbd{TAB} represents an actual tab character,
and @code{@@@kbd{NL}} represents an @samp{@@} character and end-of-line, 
i.e., when @samp{@@} is the last character on a line.)

For example,
@example
Spacey@@ @@ @@ @@
example.
@end example

@noindent produces

@example
Spacey@ @ @ @
example.
@end example

Do not follow any of these commands with braces.

To produce a non-breakable space, see @ref{@code{@@tie}}.


@node Not Ending a Sentence
@nodedescription Sometimes a .@ doesn't end a sentence.
@subsection Not Ending a Sentence

@cindex Not ending a sentence
@cindex Sentence non-ending punctuation
@cindex Periods, inserting
@cindex Spacing, in the middle of sentences
When a period, exclamation point or question mark is
at the end of a sentence, slightly more space is
inserted after it in a typeset manual.

@findex : @r{(suppress end-of-sentence space)}
@ifset commandlookup
@findex :
@end ifset
Usually, Texinfo can determine automatically when a period ends a 
sentence.  However, special commands are needed in some circumstances.
Use the @code{@@:} command after a period, question mark, exclamation
mark or colon that should not be followed by extra space.  This is 
necessary in the following situations:

@enumerate
@item After a period that ends a lowercase abbreviation which is not at 
the end of a sentence.

@item When a parenthetical remark in the middle of a sentence (like
this one!)@: ends with a period, exclamation point or question mark,
@code{@@:} should be used after the right parenthesis.  Similarly for
right brackets and right quotes (both single and double).
@end enumerate

For example:

@example
@samp{foo vs.@@: bar (or?)@@: baz},
@end example

@noindent
The first line below shows the output, and for comparison, the second 
line shows the spacing when the @samp{@@:} commands were not used.

@quotation
foo vs.@: bar (or?)@: baz@*
foo vs. bar (or?) baz
@end quotation

@iftex
If you look carefully, you will see a bit of extraneous space after the 
@samp{vs.}@: and @samp{(or?)}@:.
@end iftex

It may help you to remember what @code{@@:} does by imagining that it 
stands for an invisible lowercase character that stops a word ending in 
a period.

A few Texinfo commands force normal interword spacing, so that you
don't have to insert @code{@@:} where you otherwise would.  These are
the code-like highlighting commands, @code{@@var}, @code{@@abbr}, and
@code{@@acronym} (@pxref{Useful Highlighting}).  For example, in
@samp{@@code@{foo. bar@}} the period is not considered to be the end of a
sentence, and no extra space is inserted.

@code{@@:} has no effect on the HTML or DocBook output.


@node Ending a Sentence
@nodedescription Sometimes it does.
@subsection Ending a Sentence

@cindex Ending a Sentence
@cindex Sentence ending punctuation

@findex . @r{(end of sentence)}
@findex ! @r{(end of sentence)}
@findex ? @r{(end of sentence)}
@ifset commandlookup
@findex .
@findex !
@findex ?
@end ifset
@cindex Spacing, at ends of sentences
As mentioned above, Texinfo normally inserts additional space after
the end of a sentence.  It uses the same heuristic for this as @TeX{}:
a sentence ends with a period, exclamation point, or question mark,
either preceded or followed by optional closing punctuation, and then
whitespace, and @emph{not} preceded by a capital letter.

Use @code{@@.}@: instead of a period, @code{@@!}@: instead of an
exclamation point, and @code{@@?}@: instead of a question mark at the
end of a sentence that does end with a capital letter.  Do not put
braces after any of these commands.  For example:

@example
Give it to M.I.B. and to M.E.W@@.  Also, give it to R.J.C@@.
Give it to M.I.B. and to M.E.W.  Also, give it to R.J.C.
@end example

@noindent
The output follows.  In printed output and Info, you can see the
desired extra whitespace after the @samp{W} in the first line.

@quotation
Give it to M.I.B. and to M.E.W@.  Also, give it to R.J.C@.@*
Give it to M.I.B. and to M.E.W.  Also, give it to R.J.C.
@end quotation

In other output formats, @code{@@.}@: is equivalent to a simple @samp{.};
likewise for @code{@@!}@: and @code{@@?}@:.

@cindex Closing punctuation, and sentence ending
The ``closing punctuation'' mentioned above is defined as a right
parenthesis (@samp{)}, right bracket (@samp{]}), or right quote,
either single or double (@samp{'} and @samp{''}; the many possible
additional Unicode right quotes are not included).  These characters
can be thought of as invisible with respect to whether a given period
ends a sentence.  (This is the same rule as @TeX{}.)  For instance,
the periods in @samp{foo.) Bar} and @samp{foo.'' Bar} do end
sentences.

The meanings of @code{@@:} and @code{@@.}, etc.@: in Texinfo are
designed to work well with the Emacs sentence motion commands
(@pxref{Sentences,,, emacs, The GNU Emacs Manual}).  It may help to 
imagine that the @samp{@@} in @samp{@@.}, etc., is an invisible 
lowercase letter `a' which makes an uppercase letter before it 
immaterial for the purposes of deciding whether the period ends the 
sentence.

A few Texinfo commands are not considered as being an abbreviation,
even though they may end with a capital letter when expanded, so that
you don't have to insert @code{@@.} and companions.  Notably, this is
the case for code-like highlighting commands, @code{@@var} arguments
ending with a capital letter, @code{@@LaTeX}, and @code{@@TeX}.  For
example, that sentence ended with @samp{... @@code@{@@@@TeX@}.};
@code{@@.} was not needed.  Similarly, in
@code{... @@var@{VARNAME@}. Text} the period after @var{VARNAME} ends
the sentence; there is no need to use @code{@@.}.


@node @code{@@frenchspacing}
@nodedescription Specifying end-of-sentence spacing.
@subsection @code{@@frenchspacing} @var{val}: Control Sentence Spacing

@anchor{frenchspacing}@c old name
@findex frenchspacing
@cindex French spacing
@cindex Sentences, spacing after
@cindex Space, after sentences

In American typography, it is traditional and correct to put extra
space at the end of a sentence.  This is the default in Texinfo
(implemented in Info and printed output, not in other output formats).  In
French typography (and others), this extra space is wrong; all spaces are
uniform.

Therefore Texinfo provides the @code{@@frenchspacing} command to
control the spacing after punctuation.  It reads the rest of the line
as its argument, which must be the single word @samp{on} or @samp{off}
(always these words, regardless of the language of the document).
Here is an example:

@example
@@frenchspacing on
This is text. Two sentences. Three sentences. French spacing.

@@frenchspacing off
This is text. Two sentences. Three sentences. Non-French spacing.
@end example

@noindent produces:

@frenchspacing on
This is text. Two sentences. Three sentences. French spacing.

@frenchspacing off
This is text. Two sentences. Three sentences. Non-French spacing.

@code{@@frenchspacing} also affects the output after @code{@@.},
@code{@@!}, and @code{@@?} (@pxref{Ending a Sentence}).

@code{@@frenchspacing} has no effect on the HTML or DocBook output.


@node @code{@@dmn}
@nodedescription Formatting a dimension.
@subsection @code{@@dmn}@{@var{dimension}@}: Format a Dimension

@anchor{dmn}@c old name
@cindex Thin space between number, dimension
@cindex Dimension formatting
@cindex Format a dimension
@findex dmn

You can use the @code{@@dmn} command to format a dimension with just enough
space for proper typesetting inserted in printed output.  In other output
formats, the formatting commands insert no space at all.

To use the @code{@@dmn} command, write the number and then follow it
immediately, with no intervening space, by @code{@@dmn}, and then by
the dimension within braces.  For example,

@example
A4 paper is 8.27@@dmn@{in@} wide.
@end example

@noindent
produces

@quotation
A4 paper is 8.27@dmn{in} wide.
@end quotation

Not everyone uses this style.  Some people prefer `8.27@tie{}in.'@: or
`8.27@tie{}inches'.  In these cases, however, you need to use
@code{@@tie} (@pxref{@code{@@tie}}) or @code{@@w} (@pxref{@code{@@w}})
so that no line break can occur between the number and the dimension.
Also, if you write a period after an abbreviation within a sentence
(as with the `in.'@: above), you should write @samp{@@:} after the
period to avoid inserting extra whitespace in printed output, as shown
here.  @xref{Not Ending a Sentence}.


@node Inserting Accents
@nodedescription Inserting accents and special characters.
@section Inserting Accents

@cindex Inserting accents
@cindex Accents, inserting
@cindex Floating accents, inserting

In general, accented and other non-ASCII characters commonly used in languages
based on the Latin alphabet can be input directly as encoded characters in
Texinfo (@pxref{@code{@@documentencoding}}).  However, @@-commands are also
available for some characters, in particular if a 7-bit ASCII Texinfo source is
desired.

Here is a table with the commands Texinfo provides for inserting
floating accents.  They all need an argument, the character to accent,
which can either be given in braces as usual (@code{@@'@{e@}}), or, as
a special case, the braces can be omitted, in which case the argument
is the next character (@code{@@'e}).  This is to make the source as
convenient as possible to type and read, since accented characters are
very common in some languages.

If the command is alphabetic, such as @code{@@dotaccent}, then there
must be a space between the command name and argument if braces are
not used.  If the command is non-alphabetic, such as @code{@@'}, then
there must @emph{not} be a space; the argument is the very next
character.

Exception: the argument to @code{@@tieaccent} must be enclosed in
braces (since it is two characters instead of one).

In Info and plain text output, accent constructs are output as the true
accented characters if the document encoding supports the required characters,
unless the option @option{--disable-encoding} is given to @command{texi2any}
(@pxref{@code{@@documentencoding}}).  ASCII transliterations are used if the
encoded characters are not output.

@findex " @r{(umlaut accent)}
@cindex Umlaut accent
@findex ' @r{(acute accent)}
@cindex Acute accent
@findex = @r{(macron accent)}
@cindex Macron accent
@findex ^ @r{(circumflex accent)}
@cindex Circumflex accent
@findex ` @r{(grave accent)}
@cindex Grave accent
@findex ~ @r{(tilde accent)}
@cindex Tilde accent
@findex , @r{(cedilla accent)}
@cindex Cedilla accent
@findex dotaccent
@cindex Dot accent
@findex H @r{(Hungarian umlaut accent)}
@cindex Hungarian umlaut accent
@findex ogonek
@cindex Ogonek diacritic
@findex ringaccent
@cindex Ring accent
@findex tieaccent
@cindex Tie-after accent
@findex u @r{(breve accent)}
@cindex Breve accent
@findex ubaraccent
@cindex Underbar accent
@findex udotaccent
@cindex Underdot accent
@findex v @r{(caron)}
@cindex Hacek accent
@cindex Check accent
@cindex Caron
@ifset commandlookup
@findex "
@findex '
@findex =
@findex ^
@findex `
@findex ~
@findex ,
@findex H
@findex u
@findex v
@end ifset
@multitable {@t{@@questiondown@{@}}} {Output} {caron/hacek/check accent}
@headitem Command           @tab Output         @tab What
@item @t{@@"o}              @tab @"o            @tab umlaut accent
@item @t{@@'o}              @tab @'o            @tab acute accent
@item @t{@@,@{c@}}          @tab @,{c}          @tab cedilla accent
@item @t{@@=o}              @tab @=o            @tab macron/overbar accent
@item @t{@@^o}              @tab @^o            @tab circumflex accent
@item @t{@@`o}              @tab @`o            @tab grave accent
@item @t{@@~o}              @tab @~o            @tab tilde accent
@item @t{@@dotaccent@{o@}}  @tab @dotaccent{o}  @tab overdot accent
@item @t{@@H@{o@}}          @tab @H{o}          @tab long Hungarian umlaut
@item @t{@@ogonek@{a@}}     @tab @ogonek{a}     @tab ogonek
@item @t{@@ringaccent@{o@}} @tab @ringaccent{o} @tab ring accent
@item @t{@@tieaccent@{oo@}} @tab @tieaccent{oo} @tab tie-after accent
@item @t{@@u@{o@}}          @tab @u{o}          @tab breve accent
@item @t{@@ubaraccent@{o@}} @tab @ubaraccent{o} @tab underbar accent
@item @t{@@udotaccent@{o@}} @tab @udotaccent{o} @tab underdot accent
@item @t{@@v@{o@}}          @tab @v{o}          @tab caron/hacek/check accent
@end multitable

This table lists the Texinfo commands for inserting other characters
commonly used in languages other than English.

@findex questiondown
@cindex @questiondown{}
@findex exclamdown
@cindex @exclamdown{}
@findex aa
@cindex @aa{}
@findex AA
@cindex @AA{}
@findex ae
@cindex @ae{}
@findex AE
@cindex @AE{}
@cindex Icelandic
@cindex Eth
@findex dh
@cindex @dh{}
@findex DH
@cindex @DH{}
@findex dotless
@cindex @dotless{i} (dotless i)
@cindex @dotless{j} (dotless j)
@cindex Dotless i, j
@findex l
@cindex @l{}
@findex L
@cindex @L{}
@findex o
@cindex @o{}
@findex O
@cindex @O{}
@findex oe
@cindex @oe{}
@findex OE
@cindex @OE{}
@cindex Romance ordinals
@cindex Ordinals, Romance
@cindex Feminine ordinal
@findex ordf
@cindex @ordf{}
@cindex Masculine ordinal
@findex ordm
@cindex @ordm{}
@findex ss
@cindex @ss{}
@cindex Es-zet
@cindex Sharp S
@cindex German S
@cindex Thorn
@findex th
@cindex @th{}
@findex TH
@cindex @TH{}
@multitable {@t{@@questiondown@{@}}} {oe OE} {es-zet or sharp S}
@item @t{@@exclamdown@{@}}      @tab @exclamdown{}   @tab upside-down !
@item @t{@@questiondown@{@}}    @tab @questiondown{} @tab upside-down ?
@item @t{@@aa@{@} @@AA@{@}}     @tab @aa{} @AA{}     @tab a,A with circle
@item @t{@@ae@{@} @@AE@{@}}     @tab @ae{} @AE{}     @tab ae,AE ligatures
@item @t{@@dh@{@} @@DH@{@}}     @tab @dh{} @DH{}     @tab Icelandic eth
@item @t{@@dotless@{i@}}        @tab @dotless{i}     @tab dotless i
@item @t{@@dotless@{j@}}        @tab @dotless{j}     @tab dotless j
@item @t{@@l@{@} @@L@{@}}       @tab @l{} @L{}       @tab suppressed-L,l
@item @t{@@o@{@} @@O@{@}}       @tab @o{} @O{}       @tab O,o with slash
@item @t{@@oe@{@} @@OE@{@}}     @tab @oe{} @OE{}     @tab oe,OE ligatures
@item @t{@@ordf@{@} @@ordm@{@}} @tab @ordf{} @ordm{} @tab Spanish ordinals
@item @t{@@ss@{@}}              @tab @ss{}           @tab es-zet or sharp S
@item @t{@@th@{@} @@TH@{@}}     @tab @th{} @TH{}     @tab Icelandic thorn
@end multitable


@node Inserting Quotation Marks
@nodedescription Inserting quotation marks.
@section Inserting Quotation Marks
@cindex Inserting quotation marks
@cindex Quotation marks, inserting

@cindex Quotation characters (`'), in source
Use doubled single-quote characters to begin and end quotations:
@w{@t{`@w{}`@dots{}'@w{}'}}.  Two single quotes
are converted to left- and right-hand doubled quotation marks,
``like this''.

You may occasionally need to produce two consecutive single quotes;
for example, in documenting a computer language such as Maxima where
@t{'@w{}'} is a valid command.  You can do this with the input
@t{'@@w@{@}'}; the empty @code{@@w} command stops the combination into
the double-quote characters.

@cindex Unicode quotation characters
@cindex Grave accent @subentry vs. left quote
The left quote character (@t{`}, ASCII code 96) used in Texinfo is a
grave accent in ANSI and ISO character set standards.  We use it as a
quote character because that is how @TeX{} is set up, by default.

Texinfo supports several other quotation marks used in languages other
than English.  Below is a table with the commands Texinfo provides for
inserting quotation marks.

@cindex Single quotation marks
@cindex Double quotation marks
@cindex Left quotation marks
@cindex Right quotation marks
@findex quotedblleft
@cindex @code{`@w{}`}
@findex quoteleft
@cindex @code{`}
@cindex " (undirected double quote character)
@findex quotedblright
@cindex '@w{}'
@findex quoteright
@cindex '
@cindex Double low-9 quotation mark
@cindex Single low-9 quotation mark
@findex quotedblbase
@cindex @quotedblbase{} (double low-9 quotation mark)
@findex quotesinglbase
@cindex @quotesinglbase{} (single low-9 quotation mark)
@cindex Angle quotation marks
@cindex Guillemets
@cindex Guillemots
@cindex French quotation marks
@cindex Quotation marks, French
@cindex German quotation marks
@cindex Quotation marks, German
@cindex Double guillemets
@cindex Single guillemets
@cindex Double angle quotation marks
@cindex Single angle quotation marks
@cindex Left-pointing angle quotation marks
@cindex Right-pointing angle quotation marks
@cindex Double left-pointing angle quotation mark
@cindex Double right-pointing angle quotation mark
@cindex Single left-pointing angle quotation mark
@cindex Single right-pointing angle quotation mark
@findex guillemetleft
@findex guillemotleft
@cindex @sortas{<<} @guillemetleft{}
@findex guillemetright
@findex guillemotright
@cindex @guillemetright{}
@findex guilsinglleft
@cindex @sortas{<} @guilsinglleft{}
@findex guilsinglright
@cindex @guilsinglright{}
@c The third column doesn't have the full text in the prototype so that
@c the Info output fits within 72 columns.
@multitable {@t{@@quotedblright@{@} '@w{}'}} {Glyph} {Right-pointing double angle quotation}
@headitem Command                    @tab Glyph             @tab Unicode name (point)
@item @verb{.@quotedblleft{} ``.}    @tab @quotedblleft{}   @tab Left double quotation mark (U+201C)
@item @verb{.@quotedblright{} ''.}   @tab @quotedblright{}  @tab Right double quotation mark (U+201D)
@item @verb{.@quoteleft{} `.}        @tab @quoteleft{}      @tab Left single quotation mark (U+2018)
@item @verb{.@quoteright{} '.}       @tab @quoteright{}     @tab Right single quotation mark (U+2019)
@item @t{@@quotedblbase@{@}}         @tab @quotedblbase{}   @tab Double low-9 quotation mark (U+201E)
@item @t{@@quotesinglbase@{@}}       @tab @quotesinglbase{} @tab Single low-9 quotation mark (U+201A)
@item @t{@@guillemetleft@{@}}        @tab @guillemetleft{}  @tab Left-pointing double angle quotation mark (U+00AB)
@item @t{@@guillemetright@{@}}       @tab @guillemetright{} @tab Right-pointing double angle quotation mark (U+00BB)
@item @t{@@guilsinglleft@{@}}        @tab @guilsinglleft{}  @tab Single left-pointing angle quotation mark (U+2039)
@item @t{@@guilsinglright@{@}}       @tab @guilsinglright{} @tab Single right-pointing angle quotation mark (U+203A)
@end multitable

@cindex Auk, bird species
For the double angle quotation marks, Adobe and @LaTeX{} glyph names
are also supported:  @code{@@guillemotleft} and
@code{@@guillemotright}.  These names are incorrect; a
``guillemot'' is a bird species (a type of auk).

@cindex European Computer Modern fonts
@cindex EC fonts
The standard @TeX{} fonts support the usual quotation marks used in
English (the ones produced with single and doubled ASCII
single quotes).  For the other quotation marks, @TeX{} uses European
Computer Modern (EC) fonts (@file{ecrm1000} and other variants).
These fonts are freely available, of course; you can download them
from @url{http://ctan.org/pkg/ec}, among other places.

@cindex CM-Super fonts
The free EC fonts are bitmap fonts created with Metafont.  Especially
for on-line viewing, Type@tie{}1 (vector) versions of the fonts are
preferable; these are available in the CM-Super font package
(@url{http://ctan.org/pkg/cm-super}).

Both distributions include installation instructions.

Traditions for quotation mark usage vary to a great extent between
languages (@url{https://en.wikipedia.org/wiki/Quotation_mark}).
Texinfo does not provide commands or configurations for typesetting
quotation marks according to the numerous traditions.  Therefore, you
have to choose the commands appropriate for the language of your
manual.  Sometimes aliases (@pxref{@code{@@alias}}) can simplify the
usage and make the source code more readable.  For example, in German,
@code{@@quotedblbase} is used for the left double quote, and the right
double quote is the glyph produced by @code{@@quotedblleft}, which is
counterintuitive.  Thus, in this case the following aliases would be
convenient:

@example
@@alias lgqq = quotedblbase
@@alias rgqq = quotedblleft
@end example


@node Inserting Subscripts and Superscripts
@nodedescription Inserting sub/superscripts.
@section @code{@@sub} and @code{@@sup}: Inserting Subscripts and Superscripts

@findex sub
@findex sup
@cindex Subscripts and superscripts, text

You can insert subscripts and superscripts with the @code{@@sub}
and @code{@@sup} commands.  For example:

@example
here@@sub@{below@}@@sup@{above@}
@end example

@noindent produces:

@display
here@sub{below}@sup{above}
@end display

In Info and plain text, @code{@@sub@{@var{text}@}} is currently output
as @samp{_@{@var{text}@}} and @code{@@sup@{@var{text}@}} as
@samp{^@{@var{text}@}}, including the literal braces (to mark the
beginning and end of the ``script'' text to the reader).

When the output format (and display program) permit (printed output,
HTML), the superscript is set above the subscript when both commands are
given consecutively.

For subscripts and superscripts in mathematical expressions, it is
better to use @TeX{}'s @samp{_} and @samp{^} characters.  See the
next section.


@node Glyphs for Text
@nodedescription Inserting dots, bullets, currencies, etc.
@section Glyphs for Text

@anchor{Glyphs}@c old name
@anchor{TeX and copyright}@c another old node, now split into two
@cindex Glyphs for text
@cindex Textual glyphs

Texinfo has support for a few additional glyphs that are commonly used
in printed text but not available in ASCII@.  Of course, there are
many thousands more.  It is possible to use Unicode characters as-is
as far as @code{texi2any} is concerned, but @TeX{} is not so lucky.


@node @code{@@TeX @@LaTeX}
@nodedescription The @TeX{} logos.
@subsection @code{@@TeX}@{@} (@TeX{}) and @code{@@LaTeX}@{@} (@LaTeX{})

@anchor{tex}@c old name
@findex TeX
@findex LaTeX
@cindex Logos, @TeX{}
@cindex @TeX{} logo
@cindex @LaTeX{} logo

Use the @code{@@TeX@{@}} command to generate `@TeX{}'.  In a printed
manual, this is a special logo that is different from three ordinary
letters.  In other output formats, it just looks like @samp{TeX}.

Similarly, use the @code{@@LaTeX@{@}} command to generate `@LaTeX{}',
which is even more special in printed manuals (and different from the
incorrect @code{La@@TeX@{@}}.  In other output formats, the result is just
@samp{LaTeX}.

The spelling of these commands is unusual for Texinfo, in that they
use both uppercase and lowercase letters.


@node @code{@@copyright}
@nodedescription The copyright symbol (c in a circle).
@subsection @code{@@copyright@{@}} (@copyright{})

@anchor{copyright symbol}@c old name
@findex copyright
@cindex Copyright symbol

Use the @code{@@copyright@{@}} command to generate the copyright
symbol, `@copyright{}'.  Where possible, this is a @samp{c} inside a
circle; otherwise this is @samp{(C)}.

Legally, it's not necessary to use the copyright symbol; the English
word `Copyright' suffices, according to international treaty.


@node @code{@@registeredsymbol}
@nodedescription The registered symbol (R in a circle).
@subsection @code{@@registeredsymbol@{@}} (@registeredsymbol{})

@anchor{registered symbol}@c old name
@findex registeredsymbol
@cindex Registered symbol

Use the @code{@@registeredsymbol@{@}} command to generate the
registered symbol, `@registeredsymbol{}'.  Where possible, this is an
@samp{R} inside a circle; otherwise this is @samp{(R)}.


@node @code{@@dots}
@nodedescription How to insert ellipses: @dots{} and @enddots{}
@subsection @code{@@dots} (@dots{}) and @code{@@enddots} (@enddots{})

@anchor{dots}@c old name
@findex dots
@findex enddots
@cindex Inserting dots
@cindex Inserting ellipsis
@cindex Dots, inserting
@cindex Ellipsis, inserting

@anchor{Dots Bullets}@c old name

An @dfn{ellipsis} (a sequence of dots) would be spaced wrong when
typeset as a string of periods, so a special command is used in
Texinfo: use the @code{@@dots@{@}} command to generate a normal
ellipsis, which is three dots in a row, appropriately spaced @dots{}
like so.  To emphasize: do not simply write three periods in the input
file; that could work in some output formats, but would produce the
wrong amount of space between the periods in printed manuals.

The @code{@@enddots@{@}} command generates an end-of-sentence
ellipsis, which also has three dots, but with different spacing
afterwards, @enddots{}  Look closely to see the difference.

Here is an ellipsis: @dots{}
Here are three periods in a row: ...

In printed (and usually HTML) output, the three periods in a row are
much closer together than the dots in the ellipsis.


@node @code{@@bullet}
@nodedescription How to insert a bullet: @bullet{}
@subsection @code{@@bullet} (@bullet{})

@anchor{bullet}@c old name
@findex bullet

Use the @code{@@bullet@{@}} command to generate a large round dot, or
the closest possible thing to one.  An asterisk can also be used.
Here is a bullet: @bullet{}


@node @code{@@euro}
@nodedescription How to insert the euro currency symbol.
@subsection @code{@@euro} (@euro{}): Euro Currency Symbol

@anchor{euro}@c old name
@findex euro
@cindex Euro symbol, producing

Use the @code{@@euro@{@}} command to generate `@euro{}'.  Where
possible, this is the symbol for the Euro currency.  Otherwise, the
word @samp{Euro} is used.

@pindex feymr10
@cindex Euro font
The Euro symbol does not exist in the standard @TeX{} fonts (which
were designed before the Euro was legislated into existence).
Therefore, @TeX{} uses an additional font, named @code{feymr10} (along
with other variables).  It is freely available, of course; you can
download it from @url{http://ctan.org/pkg/eurosym}, among other
places.  The distribution includes installation instructions.


@node @code{@@pounds}
@nodedescription How to insert the pounds currency symbol.
@subsection @code{@@pounds} (@pounds{}): Pounds Sterling

@anchor{pounds}@c old name
@findex pounds
@cindex Pounds symbol

Use the @code{@@pounds@{@}} command to generate `@pounds{}'.  Where
possible, this is the symbol for the pounds sterling British currency.
@ignore
@c Unlikely to occur in user's output.
@c Occurs with "-c OUTPUT_ENCODING_NAME=ascii" or
@c "-c TEXINFO_OUTPUT_FORMAT=text".
@c See also @textdegree{}.
Otherwise, it is @samp{#}.
@end ignore


@node @code{@@textdegree}
@nodedescription How to insert the degrees symbol.
@subsection @code{@@textdegree} (@textdegree{}): Degrees Symbol

@anchor{textdegree}@c old name
@findex textdegree
@cindex Degree symbol

Use the @code{@@textdegree@{@}} command to generate `@textdegree{}'.
Where possible, this is the normal symbol for degrees.
@ignore @c see @pounds{}
Otherwise, it is an @samp{o}.
@end ignore


@node @code{@@minus}
@nodedescription How to insert a minus sign.
@subsection @code{@@minus} (@minus{}): Inserting a Minus Sign

@anchor{minus}@c old name
@findex minus
@cindex Minus sign

@cindex Em dash, compared to minus sign
@cindex Hyphen, compared to minus
Use the @code{@@minus@{@}} command to generate a minus sign.
Where the character encoding and font used in the output allow it,
the symbol is the customary length for a minus sign---a little longer
than a hyphen, shorter than an em-dash:

@display
@samp{@minus{}} is a minus sign generated with @samp{@@minus@{@}},

`-' is a hyphen generated with the character @samp{-},

`---' is an em-dash for text.
@end display

If you actually want to typeset some math that does a subtraction, it
is better to use @code{@@math}, as in @code{@@math@{a-b@}} (@pxref{Inserting
Math}).


@node @code{@@geq @@leq}
@nodedescription How to insert greater/less-than-or-equal signs.
@subsection @code{@@geq} (@geq{}) and @code{@@leq} (@leq{}): Inserting Relations

@anchor{geq leq}@c old name
@findex geq
@findex leq

Use the @code{@@geq@{@}} and @code{@@leq@{@}} commands to generate
greater-than-or-equal and less-than-equal-signs, `@geq{}' and
`@leq{}'.  When those symbols are not available, the ASCII sequences
@samp{>=} and @samp{<=} are output.


@node Glyphs for Programming
@nodedescription Indicating results of evaluation, expansion of macros, errors, etc.
@section Glyphs for Programming

@cindex Glyphs for programming
@cindex Examples, glyphs for
@cindex Programming, glyphs for

In Texinfo, code is often illustrated in examples that are delimited
by @code{@@example} and @code{@@end example}.  In such examples,
you can indicate the results of evaluation or an expansion using
@samp{@result{}} or @samp{@expansion{}}.  Likewise, there are commands
to insert glyphs to indicate printed output, error messages, equivalence
of expressions, the location of point in an editor, and GUI operation
sequences.

The glyph-insertion commands do not need to be used within an example,
but most often they are.  All glyph-insertion commands are followed by
empty braces.


@node Glyphs Summary
@nodedescription List of the glyph commands.
@subsection Glyphs Summary

Here is a summary of the glyph commands:

@table @asis
@item @result{}
@code{@@result@{@}} indicates the result of an expression.

@item @expansion{}
@code{@@expansion@{@}} indicates the results of a macro expansion.

@item @print{}
@code{@@print@{@}} indicates printed output.

@item @error{}
@code{@@error@{@}} indicates the following text is an error message.

@item @equiv{}
@code{@@equiv@{@}} indicates the exact equivalence of two forms.

@item @point{}
@code{@@point@{@}} shows the location of point.

@item @clicksequence{A @click{} B}
@code{@@clicksequence@{A @@click@{@} B@}} indicates a GUI operation
sequence: first A, then clicking B, or choosing B from a menu, or
otherwise selecting it.
@end table


@node @code{@@result}
@nodedescription How to show the result of expression.
@subsection @code{@@result@{@}} (@result{}): Result of an Expression

@anchor{result}@c old name
@findex result
@cindex Result of an expression
@cindex Indicating evaluation
@cindex Evaluation glyph
@cindex Value of an expression, indicating

Use the @code{@@result@{@}} command to indicate the result of
evaluating an expression.

The @code{@@result@{@}} command is displayed as @samp{@result{}},
either a double stemmed arrow or (when that is not available) the
ASCII sequence @samp{=>}.

Thus, the following,

@example lisp
(cdr '(1 2 3))
    @result{} (2 3)
@end example

@noindent
may be read as ``@code{(cdr '(1 2 3))} evaluates to @code{(2 3)}''.


@node @code{@@expansion}
@nodedescription How to indicate an expansion.
@subsection @code{@@expansion@{@}} (@expansion{}): Indicating an Expansion

@anchor{expansion}@c old name
@cindex Expansion, indicating
@cindex Macro expansion, indicating
@findex expansion

When an expression is a macro call, it expands into a new expression.
You can indicate the result of the expansion with the
@code{@@expansion@{@}} command.

The @code{@@expansion@{@}} command is displayed as
@samp{@expansion{}}, either a long arrow with a flat base or (when
that is not available) the ASCII sequence @samp{==>}.

@need 700
For example, the following

@example
@group
@@example lisp
(third '(a b c))
    @@expansion@{@} (car (cdr (cdr '(a b c))))
    @@result@{@} c
@@end example
@end group
@end example

@noindent
produces

@example lisp
@group
(third '(a b c))
    @expansion{} (car (cdr (cdr '(a b c))))
    @result{} c
@end group
@end example

@noindent
which may be read as:

@quotation
@code{(third '(a b c))} expands to @code{(car (cdr (cdr '(a b c))))};
the result of evaluating the expression is @code{c}.
@end quotation

@noindent
Often, as in this case, an example looks better if the
@code{@@expansion@{@}} and @code{@@result@{@}} commands are indented.


@node @code{@@print}
@nodedescription How to indicate generated output.
@subsection @code{@@print@{@}} (@print{}): Indicating Generated Output

@anchor{Print Glyph}@c old name
@findex print
@cindex Printed output, indicating

Sometimes an expression will generate output during its execution.
You can indicate such displayed output with the @code{@@print@{@}}
command.

The @code{@@print@{@}} command is displayed as @samp{@print{}}, either
a horizontal dash butting against a vertical bar or (when that is not
available) the ASCII sequence @samp{-|}.

In the following example, the printed text is indicated with
@samp{@print{}}, and the value of the expression follows on the
last line.

@example lisp
@group
(progn (print 'foo) (print 'bar))
    @print{} foo
    @print{} bar
    @result{} bar
@end group
@end example

@noindent
In a Texinfo source file, this example is written as follows:

@example
@group
@@example lisp
(progn (print 'foo) (print 'bar))
    @@print@{@} foo
    @@print@{@} bar
    @@result@{@} bar
@@end example
@end group
@end example


@node @code{@@error}
@nodedescription How to indicate an error message.
@subsection @code{@@error@{@}} (@error{}): Indicating an Error Message

@anchor{Error Glyph}@c old name
@cindex Error message, indicating
@findex error

A piece of code may cause an error when you evaluate it.  You can
designate the error message with the @code{@@error@{@}} command.

The @code{@@error@{@}} command is displayed as @samp{@error{}}, either
the word `error' in a box in the printed output, the word error
followed by an arrow in other formats or (when no arrow is available)
@samp{error-->}.

@need 700
Thus,

@example
@@example lisp
(+ 23 'x)
@@error@{@} Wrong type argument: integer-or-marker-p, x
@@end example
@end example

@noindent
produces

@example lisp
(+ 23 'x)
@error{} Wrong type argument: integer-or-marker-p, x
@end example

@noindent
This indicates that the following error message is printed
when you evaluate the expression:

@example lisp
Wrong type argument: integer-or-marker-p, x
@end example

The word @samp{@error{}} itself is not part of the error message.


@node @code{@@equiv}
@nodedescription How to indicate equivalence.
@subsection @code{@@equiv@{@}} (@equiv{}): Indicating Equivalence

@anchor{Equivalence}@c oldname
@cindex Equivalence, indicating
@findex equiv

Sometimes two expressions produce identical results.  You can indicate
the exact equivalence of two forms with the @code{@@equiv@{@}}
command.  The @code{@@equiv@{@}} command is displayed as
@samp{@equiv{}}, either a standard mathematical equivalence sign
(three parallel horizontal lines) or (when that is not available) as
the ASCII sequence @samp{==}.

Thus,

@example
@@example lisp
(make-sparse-keymap) @@equiv@{@} (list 'keymap)
@@end example
@end example

@noindent
produces

@example lisp
(make-sparse-keymap) @equiv{} (list 'keymap)
@end example

@noindent
This indicates that evaluating @code{(make-sparse-keymap)} produces
identical results to evaluating @code{(list 'keymap)}.


@node @code{@@point}
@nodedescription How to indicate the location of point.
@subsection @code{@@point@{@}} (@point{}): Indicating Point in a Buffer

@anchor{Point Glyph}@c old name
@cindex Point, indicating in a buffer
@findex point

Sometimes you need to show an example of text in an Emacs buffer.  In
such examples, the convention is to include the entire contents of the
buffer in question between two lines of dashes containing the buffer
name.

You can use the @samp{@@point@{@}} command to show the location of
point in the text in the buffer.  (The symbol for point, of course, is
not part of the text in the buffer; it indicates the place
@emph{between} two characters where point is located.)

The @code{@@point@{@}} command is displayed as @samp{@point{}}, either
a pointed star or (when that is not available) the ASCII sequence
@samp{-!-}.

The following example shows the contents of buffer @file{foo} before
and after evaluating a Lisp command to insert the word @code{changed}.

@example
@group
---------- Buffer: foo ----------
This is the @point{}contents of foo.
---------- Buffer: foo ----------

@end group
@end example

@example
@group
(insert "changed ")
    @result{} nil
---------- Buffer: foo ----------
This is the changed @point{}contents of foo.
---------- Buffer: foo ----------

@end group
@end example

In a Texinfo source file, the example is written like this:

@example
@@example
---------- Buffer: foo ----------
This is the @@point@{@}contents of foo.
---------- Buffer: foo ----------

(insert "changed ")
    @@result@{@} nil
---------- Buffer: foo ----------
This is the changed @@point@{@}contents of foo.
---------- Buffer: foo ----------
@@end example
@end example


@node Click Sequences
@nodedescription Inserting GUI usage sequences.
@subsection Click Sequences

@cindex Click sequences
@cindex Sequence of clicks
@cindex GUI click sequence

@findex clicksequence
When documenting graphical interfaces, it is necessary to describe
sequences such as `Click on @samp{File}, then choose @samp{Open}, then
@dots{}'.  Texinfo offers commands @code{@@clicksequence} and
@code{click} to represent this, typically used like this:

@example
@dots{} @@clicksequence@{File @@click@{@} Open@} @dots{}
@end example

@noindent
which produces:

@display
@dots{} @clicksequence{File @click{} Open} @dots{}
@end display

@findex click
@findex arrow
The @code{@@click} command produces a right arrow; this glyph is also
available independently via the command @code{@@arrow@{@}}.


@node Inserting Unicode
@nodedescription Inserting a Unicode character by code point.
@section Inserting Unicode: @code{@@U}

@cindex Unicode character, inserting
@cindex Code point of Unicode character, inserting by
@findex U

The command @code{@@U@{@var{hex}@}} inserts a representation of the
Unicode character U+@var{hex}.  For example, @code{@@U@{0132@}}
inserts the Dutch `IJ' ligature (`@U{0132}').

The @var{hex} value should be at least four hex digits; leading zeros
are @emph{not} added.  In general, @var{hex} must specify a valid
normal Unicode character; e.g., U+10FFFF (the very last code point) is
invalid by definition, and thus cannot be inserted this way.

@cindex ASCII, source document portability using
@code{@@U} is useful for inserting occasional glyphs for which Texinfo
has no dedicated command, while allowing the Texinfo source to remain
purely 7-bit ASCII for maximum portability.

@cindex Unicode and @TeX{}
This command has many limitations---the same limitations as inserting
Unicode characters in UTF-8 or another binary form.  First and most
importantly, @TeX{} knows nothing about most of Unicode.  Supporting
specific additional glyphs upon request is possible, but it's not
viable for @file{texinfo.tex} to support whole additional scripts
(Japanese, Urdu, @dots{}).  The @code{@@U} command does nothing to
change this.  If the specified character is not supported in @TeX{},
an error is given.  @LaTeX{} output has more possibilities regarding
UTF-8, but could require extra code to load fonts and declare
how UTF-8 characters are output.  (@xref{@code{@@documentencoding}}.)

@cindex Entity reference in HTML et al.
@cindex @samp{&#x@var{hex};}, output from @code{@@U}
In HTML and DocBook, the output from @code{@@U} is always an
entity reference of the form @samp{&#x@var{hex};}, as in
@samp{&#x0132;} for the example above.  This should work even when an
HTML document uses some other encoding (say, Latin@tie{}1) and the
given character is not supported in that encoding.

In Info and plain text, if the output encoding is not UTF-8, the output 
is the ASCII sequence @samp{U+@var{hex}}, as in the six ASCII characters 
@samp{U+0132} for the example above.


@node Inserting Math
@nodedescription Formatting mathematical expressions.
@chapter Formatting Mathematics

@anchor{math}@c old name
@findex math
@cindex Mathematical expressions, inserting
@cindex Formulas, mathematical
You can write a mathematical expression, equation or formula using
the @code{@@math} command.  Write the @TeX{} math notation between
braces, like this:

@example
@@math@{\partial_\alpha \partial^\alpha A^\beta = \mu_0 J^\beta@}
@end example

@code{@@math} is formatted inline when used inside a paragraph,
like @math{\partial_\alpha \partial^\alpha A^\beta = \mu_0 J^\beta} in
this example.

By default, the @code{@@math} command has no special effect on the Info
output, merely outputting the contents verbatim.  You can use the
experimental @code{INFO_MATH_IMAGES} variable to produce images; see
@ref{Info and Plaintext Customization Variables}.

For printed output, @code{@@math} switches into @TeX{} ``math mode''.
In that context, @samp{\} must be used instead of @samp{@@}
for plain @TeX{} math control sequences for symbols, functions,
and so on.

@cindex Math output for HTML
@cindex HTML output @subentry math
By default, the HTML output is only emphasized.
@command{texi2any} provides three options for displaying properly
formatted mathematics for HTML.  You can select these with the
@code{HTML_MATH} variable (@pxref{HTML Customization for Math}).
With @code{HTML_MATH} set to @samp{l2h}, @command{texi2any} attempts
to use the @command{latex2html} program to produce image files for
mathematical material.  With the @samp{t4h} setting, @command{texi2any}
attempts to use the @command{tex4ht} program.  With the @samp{mathjax}
setting, @command{texi2any} inserts references in the output files
to MathJax scripts to format the material.  The MathJax option
requires JavaScript to be enabled in the browser to work.  See also
@ref{MathJax Customization Variables}, @ref{@command{latex2html}
Customization Variables} and @ref{@command{tex4ht} Customization
Variables}.

@cindex Displayed equations
@cindex Equations, displayed
@findex displaymath
For displayed equations, you can use the @code{@@displaymath}
command.  Example:

@example
@@displaymath
f(x) = @{1\over\sigma\sqrt@{2\pi@}@}
e^@{-@{1\over2@}\left(@{x-\mu\over\sigma@}\right)^2@}
@@end displaymath
@end example

@noindent which produces:

@displaymath
f(x) = {1\over\sigma\sqrt{2\pi}}
e^{-{1\over2}\left({x-\mu\over\sigma}\right)^2}
@end displaymath

In general, the contents of @code{@@math} or @code{@@displaymath}
should be plain @TeX{} only, with no interspersed Texinfo commands.
If you do use any Texinfo commands, then you should mark these with
@samp{@@} as usual, rather than @samp{\} (e.g.@: @samp{@@var} rather than
@samp{\var}), but we do not guarantee which Texinfo commands will work.

Although @code{@@sub} and @code{@@sup} may work inside math mode in
some contexts, it is better to use @TeX{}'s @samp{_} and @samp{^}
characters to denote subscripts and superscripts within mathematical
expressions.

@LaTeX{}-specific code will only work when the output format is @LaTeX{},
and with the @code{HTML_MATH} options (although @command{tex4ht} needs
@code{T4H_MATH_CONVERSION} to be set to @samp{latex};
@pxref{@command{tex4ht} Customization Variables}).

@ignore
@findex @sortas{\} \ @r{(literal \ in @code{@@math})}
Since @samp{\} is an escape character inside @code{@@math}, you can
use @code{@@\} to get a literal backslash (@code{\\} will work in
@TeX{}, but you'd get the literal two characters @samp{\\} in Info).
@code{@@\} is not defined outside of @code{@@math}, since a @samp{\}
ordinarily produces a literal (typewriter) @samp{\}.  You can also use
@code{@@backslashchar@{@}} in any mode to get a typewriter backslash.
@xref{Inserting a Backslash}.
@end ignore

@findex \mathopsup
Due to the conflict with Texinfo's @code{@@sup} command, you can access
the plain @TeX{} command @code{\sup} as @code{\mathopsup} instead,
in the unlikely occurrence that you want to do this (but only when
processing with @TeX{}, not when outputting @LaTeX{} nor with any of the
@code{HTML_MATH} options).


@node Breaks
@nodedescription Forcing or preventing line and page breaks.
@chapter Forcing and Preventing Breaks

@cindex Forcing line and page breaks
@cindex Making line and page breaks
@cindex Preventing line and page breaks
@cindex Line breaks @subentry awkward
@cindex Page breaks, awkward

Line and page breaks can sometimes occur in the `wrong' place in one
or another form of output.  It's up to you to ensure that text looks
right in all the output formats.

For example, in a printed manual, page breaks may occur awkwardly in
the middle of an example; to prevent this, you can hold text together
using a grouping command that keeps the text from being split across
two pages.  Conversely, you may want to force a page break where none
would normally occur.

You can use the break, break prevention, or pagination commands to fix
problematic line and page breaks.


@node Break Commands
@nodedescription Summary of break-related commands.
@section Break Commands

The break commands create or allow line and paragraph breaks:

@table @code
@item @@*
Force a line break.

@item @@sp @var{n}
Skip @var{n} blank lines.

@item @@-
Insert a discretionary hyphen.

@item @@hyphenation@{@var{hy-phen-a-ted words}@}
Define hyphen points in @var{hy-phen-a-ted words}.
@end table

These commands hold text together on a single line:

@table @code
@item @@w@{@var{text}@}
Prevent @var{text} from being split and hyphenated across two lines.

@item @@tie@{@}
Insert a normal interword space at which a line break may not occur.
@end table

The pagination commands apply only to printed output, since other
output formats do not have pages.

@table @code
@item @@page
Start a new page.

@item @@group
Hold text together that must appear on one page.

@item @@need @var{mils}
Start a new page if not enough space on this one.
@end table


@node Line Breaks
@nodedescription Forcing line breaks.
@section @code{@@*} and @code{@@/}: Generate and Allow Line Breaks

@findex * @r{(force line break)}
@findex / @r{(allow line break)}
@ifset commandlookup
@findex *
@findex /
@end ifset

@cindex Line breaks @subentry controlling
@cindex Controlling line breaks
@cindex Breaks in a line
@cindex Force line break
@cindex Allow line break

The @code{@@*} command forces a line break in all output formats.
The @code{@@/} command allows a line break (printed manual only).

Here is an example with @code{@@*}:

@example
This sentence is broken @@*into two lines.
@end example

@noindent produces

@example
@group
This sentence is broken
into two lines.
@end group
@end example

The @code{@@/} command can be useful within long URLs or other
identifiers where @TeX{} can't find a good place to break.  @TeX{}
will automatically break URLs at the natural places (@pxref{URL Line
Breaking}), so only use @code{@@/} if you need it.  @code{@@/} has no
effect on the other output formats.


@node @code{@@- @@hyphenation}
@nodedescription Helping @TeX{} with hyphenation points.
@section @code{@@-} and @code{@@hyphenation}: Hyphenation in Printed Output

@anchor{- and hyphenation}@c old name
@findex @sortas{-} - @r{(discretionary hyphen)}
@ifset commandlookup
@findex @sortas{-} -
@end ifset
@findex hyphenation
@cindex Hyphenation, helping @TeX{} do
@cindex Fine-tuning, and hyphenation

Although @TeX{}'s hyphenation algorithm is generally pretty good, it
does miss useful hyphenation points from time to time.  (Or, far more
rarely, insert an incorrect hyphenation.)  So, for documents with an
unusual vocabulary or when fine-tuning for a printed edition, you may
wish to specify hyphenation points explicitly.  Texinfo supports two
commands for this:

@table @code
@item @@-

Insert a discretionary hyphen, i.e., a place where a word can be
broken across lines with a hyphen.  This is especially useful when you
notice that an overfull hbox is due to @TeX{} missing a hyphenation
(@pxref{Overfull hboxes}).  @TeX{} will not insert any hyphenation
points itself into a word containing @code{@@-}.

@item @@hyphenation@{@var{hy-phen-a-ted words}@}
Give hyphenation points for certain words.  For example:
@example
@@hyphenation@{man-u-script man-u-scripts@}
@end example

@noindent As shown, you put a @samp{-} at each hyphenation point.
@TeX{} only uses the specified hyphenation points when the words match
exactly, so give all necessary variants, such as plurals.
@end table

Non-printed output is not hyphenated, so none of
these commands have any effect in other output formats.


@node @code{@@allowcodebreaks}
@nodedescription Controlling line breaks within @@code text.
@section @code{@@allowcodebreaks}: Control Line Breaks in @code{@@code}

@anchor{allowcodebreaks}@c old name
@findex allowcodebreaks
@cindex Breaks, within @code{@@code}
@cindex @sortas{-} -, breakpoint within @code{@@code}
@cindex Hyphen, breakpoint within @code{@@code}
@cindex Dash, breakpoint within @code{@@code}
@cindex _, breakpoint within @code{@@code}
@cindex Underscore, breakpoint within @code{@@code}

Ordinarily, @TeX{} considers breaking lines at @samp{-} and @samp{_}
characters within @code{@@code} and related commands
(@pxref{@code{@@code}}), more or less as if they were ``empty''
hyphenation points.

This is necessary since many manuals, especially for Lisp-family
languages, must document very long identifiers.  On the other hand,
some manuals don't have this problem, and you may not wish to allow a
line break at the underscore in, for example, @code{SIZE_MAX}, or even
worse, after any of the four underscores in @code{__typeof__}.

So Texinfo provides this command:

@example
@@allowcodebreaks false
@end example

@noindent to prevent from breaking at @samp{-} or @samp{_} within
@code{@@code}.  You can go back to allowing such breaks with
@code{@@allowcodebreaks true}.  Write these commands on lines by
themselves.

These commands can be given anywhere in the document.  For example,
you may have just one problematic paragraph where you need to turn off
the breaks, but want them in general, or vice versa.

This command has no effect except in @TeX{} output.


@node @code{@@w}
@nodedescription Preventing unwanted line breaks in text.
@section @code{@@w}@{@var{text}@}: Prevent Line Breaks

@anchor{w}@c old name
@findex w
@cindex Line breaks, preventing

@code{@@w@{@var{text}@}} outputs @var{text}, while prohibiting line
breaks within @var{text}.

@cindex Non-breakable space, fixed
@cindex Unbreakable space, fixed
Thus, you can use @code{@@w} to produce a non-breakable space, fixed at
the width of a normal interword space:

@example
@@w@{ @} @@w@{ @} @@w@{ @} indentation.
@end example

@noindent produces:

@display
@w{ } @w{ } @w{ } indentation.
@end display

The space from @code{@@w@{@w{ }@}}, as well as being non-breakable,
also will not stretch or shrink.  Sometimes that is what you want, for
instance if you're doing manual indenting.  However, usually you want
a normal interword space that does stretch and shrink (in the printed
output); for that, see the @code{@@tie} command in the next section.

@cindex Hyphenation, preventing
In printed output, you can also use the @code{@@w} command to prevent
a long name or phrase being automatically hyphenated, for example if
it happens to fall near the end of a line.

@cindex Keyword expansion, preventing
@cindex Version control keywords, preventing expansion of
@cindex $Id expansion, preventing
You can also use @code{@@w} to avoid unwanted keyword expansion in
source control systems.  For example, to literally write @t{@w{$}Id$}
in your document, use @code{@@w@{$@}Id$}.  This trick isn't effective
for output files in some output formats, though.


@node @code{@@tie}
@nodedescription Inserting an unbreakable but varying space.
@section @code{@@tie@{@}}: Inserting an Unbreakable Space

@anchor{tie}@c old name
@findex tie
@cindex Tied space
@cindex Non-breakable space, variable
@cindex Unbreakable space, variable

The @code{@@tie@{@}} command produces a normal interword space at which
a line break may not occur.  Always write it with following (empty)
braces, as usual for commands used within a paragraph.  Here's an
example:

@example
@@TeX@{@} was written by Donald E.@@tie@{@}Knuth.
@end example

@noindent produces:

@display
@TeX{} was written by Donald E.@tie{}Knuth.
@end display

There are two important differences between @code{@@tie@{@}} and
@code{@@w@{@w{ }@}}:

@itemize
@item
The space produced by @code{@@tie@{@}} will stretch and shrink slightly
along with the normal interword spaces in the paragraph; the space
produced by @code{@@w@{@w{ }@}} will not vary.

@item
@code{@@tie@{@}} allows hyphenation of the surrounding words, while
@code{@@w@{@w{ }@}} inhibits hyphenation of those words (for @TeX{}nical
reasons, namely that it produces an @samp{\hbox}).

@end itemize


@node @code{@@sp}
@nodedescription Inserting blank lines.
@section @code{@@sp @var{n}}: Insert Blank Lines

@anchor{sp}@c old name
@findex sp
@cindex Space, inserting vertical
@cindex Blank lines
@cindex Line spacing

A line beginning with and containing only @code{@@sp @var{n}}
generates @var{n} blank lines of space.  @code{@@sp} also
forces a paragraph break.  For example,

@example
@@sp 2
@end example

@noindent
generates two blank lines.

The @code{@@sp} command is most often used inside a @code{@@titlepage}
block.


@node @code{@@page}
@nodedescription Forcing the start of a new page.
@section @code{@@page}: Start a New Page

@anchor{page}@c old name
@findex page
@cindex Page breaks, forcing

A line containing only @code{@@page} starts a new page in a printed
manual.  In other formats, without the concept of pages, it starts a
new paragraph.  A @code{@@page} command is often used in a
@code{@@titlepage} section of a Texinfo file to start the copyright
page.


@node @code{@@group}
@nodedescription Preventing unwanted page breaks.
@section @code{@@group}: Prevent Page Breaks

@anchor{group}@c old name
@findex group
@cindex Group (hold text together vertically)
@cindex Holding text together vertically
@cindex Vertically holding text together

The @code{@@group} command is used to hold an example
together on one page.  Use it inside an
@code{@@example} or similar construct to begin an unsplittable vertical
group, which will appear entirely on one page in the printed output.
Terminate the group by a line containing only @code{@@end group}.
This command has an effect in @TeX{} output only.

@need 750
The @code{@@group} and @code{@@end group} commands need to be inside the
@code{@@example} and @code{@@end example} commands, thus:

@example
@group
@@example
@@group
@dots{}
@@end group
@@end example
@end group
@end example

Although @code{@@group} would make sense conceptually in a wide
variety of contexts, its current implementation works only
within @code{@@example} and variants, and within @code{@@display},
@code{@@format}, @code{@@flushleft} and @code{@@flushright}.
@xref{Quotations and Examples}.  (What all these commands have in
common is that each line of input produces a line of output.)

@c  In other contexts, @code{@@group} can cause anomalous vertical
@c  spacing.

@c commented out below because all TeX errors are strange and unfathomable,
@c not just for @group

@c If you forget to end a group, you may get strange and unfathomable
@c error messages when you run @TeX{}.  This is because @TeX{} keeps
@c trying to put the rest of the Texinfo file onto the one page and does
@c not start to generate error messages until it has processed
@c considerable text.  It is a good rule of thumb to look for a missing
@c @code{@@end group} if you get incomprehensible error messages in
@c @TeX{}.


@node @code{@@need}
@nodedescription Another way to prevent unwanted page breaks.
@section @code{@@need @var{mils}}: Prevent Page Breaks

@anchor{need}@c old name
@findex need
@cindex Need space at page bottom
@cindex Mils, argument to @code{@@need}

A line containing only @code{@@need @var{n}} starts a new page in a
printed manual if fewer than @var{n} mils (thousandths of an inch)
remain on the current page.  Do not use braces around the argument
@var{n}.  The @code{@@need} command has no effect on other output
formats since they are not paginated.

@need 800
This paragraph is preceded by a @code{@@need} command that starts a
new page in printed output if fewer than 800 mils (eight-tenths inch)
remain on the page.  It looks like this:

@example
@group
@@need 800
This paragraph is preceded by @dots{}
@end group
@end example

@cindex Orphans, preventing
The @code{@@need} command is useful for preventing orphans: single
lines at the bottoms of printed pages.


@node Definition Commands
@nodedescription Describing functions and the like uniformly.
@chapter Definition Commands
@cindex Definition commands

The @code{@@deffn} command and the other @dfn{definition commands}
enable you to describe functions, variables, macros, commands, user
options, special forms and other entities in a uniform format.

In the output, the name of the entity is shown with any arguments, along
with the entity category ---`Function', `Variable', or whatever.
Underneath, the body of the definition is indented.
The name of the entity is also entered into the appropriate index.

All the definition commands follow a similar format.  This chapter
starts by describing @code{@@deffn} before detailing all the other
definition commands.


@node Def Cmd Template
@nodedescription Writing descriptions using definition commands.
@section The Template for a Definition
@cindex Definition template
@cindex Template for a definition

@example
@group
@@deffn @var{category} @var{name} @var{arguments}@dots{}
@var{body-of-definition}
@@end deffn
@end group
@end example

@noindent
The @code{@@deffn} command is used for definitions of entities that
resemble functions---entities that may take arguments.
Write the @code{@@deffn} command at the beginning of a line
and follow it on the same line by the category of the entity, the name
of the entity itself, and its arguments (if any).  Then write the body
of the definition on succeeding lines.
Finally, end the definition with an @code{@@end deffn} command
written on a line of its own.


@need 700
@noindent
For example,

@example
@group
@@deffn Command forward-word count
This command moves point forward @@var@{count@} words
(or backward if @@var@{count@} is negative). @dots{}
@@end deffn
@end group
@end example

@noindent
produces

@quotation
@deffn Command forward-word count
This command moves point forward @var{count} words
(or backward if @var{count} is negative). @dots{}
@end deffn
@end quotation

Capitalize the category name like a title.  If the name of the
category contains spaces, as in the phrase `Interactive Command',
enclose it in braces.  For example:

@example
@group
@@deffn @{Interactive Command@} isearch-forward
@dots{}
@@end deffn
@end group
@end example

@noindent
Otherwise, the second word will be mistaken for the name of the
entity.  As a general rule, when any of the arguments in the heading
line @emph{except} the last one are more than one word, you need to
enclose them in braces.  This may also be necessary if the text
contains commands, for example, @samp{@{declaraci@@'on@}} if you are
writing in Spanish.

The category is output in a different location for different output
formats.  For example, in the Info file, the category appears at the
beginning of the first line of the definition.  With @TeX{} output,
the category is printed next to the right margin.

@code{@@deffn} enters names into the index of functions.

Three predefined, specialized variations of @code{@@deffn}
(@code{@@defun}, @code{@@defmac}, and @code{@@defspec}) specify the
category for you: ``Function'', ``Macro'', and ``Special Form''
respectively.  (In Lisp, a special form is an entity much like a
function.)  Similarly, the general @code{@@defvr} command is
accompanied by several specialized variations for describing
particular kinds of variables.


@node Def Cmd Continuation Lines
@nodedescription Continuing the heading over source lines.
@section Definition Command Continuation Lines
@cindex Continuation lines in definition commands
@cindex Definition command headings, continuing
@cindex @sortas{@@} @samp{@@} as continuation in definition commands

The heading line of a definition command can get very long.
Therefore, Texinfo has a special syntax allowing them to be continued
over multiple lines of the source file: a lone @samp{@@} at the end of
each line to be continued.  Here's an example:

@example
@@defun fn-name @@
  arg1 arg2 arg3
This is the basic continued defun.
@@end defun
@end example

@noindent produces:

@defun fn-name   arg1 arg2 arg3
This is the basic continued defun.
@end defun

@noindent
As you can see, the continued lines are combined, as if they had been
typed on one source line.

Although this example only shows a one-line continuation,
continuations may extend over any number of lines, in the same way;
put an @code{@@} at the end of each line to be continued.

@cindex Whitespace, collapsed around continuations
@cindex Collapsing whitespace around continuations
In general, any number of spaces or tabs before the @code{@@}
continuation character are collapsed into a single space.  There is one
exception: the Texinfo processors will not fully collapse whitespace
around a continuation inside braces.  For example:

@example
@@deffn @{Category @@
  Name@} @dots{}
@end example

@noindent The output (not shown) has excess space between `Category'
and `Name'.  To avoid this, elide the unwanted whitespace in your
input, or put the continuation @code{@@} outside braces.

@code{@@} does not function as a continuation character in @emph{any}
other context.  Ordinarily, @samp{@@} followed by a whitespace
character (space, tab, newline) produces a normal interword space
(@pxref{Multiple Spaces}).


@node Optional Arguments
@nodedescription Handling optional and repeated arguments.
@section Optional and Repeated Arguments
@cindex Optional and repeated arguments
@cindex Repeated and optional arguments
@cindex Arguments, repeated and optional
@cindex Syntax, optional & repeated arguments
@cindex Meta-syntactic chars for arguments

@c This is consistent with the Emacs Lisp Reference Manual.
Some entities take optional or repeated arguments.  One convention for
indicating these uses square brackets and ellipses: an argument enclosed
within square brackets is optional, and an argument followed by an
ellipsis is optional and may be repeated more than once.

Thus, [@var{optional-arg}] means that @var{optional-arg} is optional
and @var{repeated-args}@code{@dots{}} stands for zero or more
arguments.  Parentheses are used when several arguments are grouped
into additional levels of list structure in Lisp.

Here is the definition line of an example of an imaginary
(complicated) special form:

@quotation
@defspec foobar (var [from to [inc]]) body@dots{}
@end defspec
@end quotation

@noindent
In this example, the arguments @var{from} and @var{to} are optional,
but must both be present or both absent.  If they are present,
@var{inc} may optionally be specified as well.  These arguments are
grouped with the argument @var{var} into a list, to distinguish them
from @var{body}, which includes all remaining elements of the
form.

In a Texinfo source file, this @code{@@defspec} line is written like
this:

@example
@@defspec foobar (var [from to [inc]]) body@@dots@{@}
@end example


@node No Space After Definition Name
@nodedescription How to omit space after name.
@section Omitting the Space After a Definition Name

@vindex txidefnamenospace
As a matter of style or as demanded by the syntax of a programming language,
you may wish to omit any space after a name in a definition, occurring
before an opening bracket.  To do this, set the @samp{txidefnamenospace}
flag (@pxref{@code{@@set @@value}}).  For example, this input

@example
@@set txidefnamenospace
@@deffn Builtin m4_index (string, substring)
@@dots@{@}
@@end deffn
@end example

@noindent produces the following:

@set txidefnamenospace
@deffn Builtin m4_index (string, substring)
@dots{}
@end deffn
@clear txidefnamenospace


@node @code{@@deffnx}
@nodedescription Group two or more `first' lines.
@section @code{@@deffnx}, et al.: Two or More `First' Lines

@anchor{deffnx}@c old node
@findex deffnx
@cindex Two `First' Lines for @code{@@deffn}
@cindex Grouping two definitions together
@cindex Definitions grouped together

To create two or more `first' or header lines for a definition, follow
the first @code{@@deffn} line by a line beginning with
@code{@@deffnx}.

@need 1000
For example,

@example
@group
@@deffn @{Interactive Command@} isearch-forward
@@deffnx @{Interactive Command@} isearch-backward
These two search commands are similar except @dots{}
@@end deffn
@end group
@end example

@noindent
produces

@deffn {Interactive Command} isearch-forward
@deffnx {Interactive Command} isearch-backward
These two search commands are similar except @dots{}
@end deffn

@findex defcvx
@findex defivarx
@findex defmacx
@findex defmethodx
@findex defoptx
@findex defopx
@findex defspecx
@findex deftpx
@findex deftypecvx
@findex deftypefnx
@findex deftypefunx
@findex deftypeivarx
@findex deftypemethodx
@findex deftypeopx
@findex deftypevarx
@findex deftypevrx
@findex defunx
@findex defvarx
@findex defvrx
Each definition command has an `x' form: @code{@@defunx},
@code{@@defvrx}, @code{@@deftypefunx}, etc.

The `x' forms work similarly to @code{@@itemx}
(@pxref{@code{@@itemx}}).


@node Def Cmds in Detail
@nodedescription Reference for all the definition commands.
@section The Definition Commands

This section describes all the definition commands of Texinfo.


@node Functions Commands
@nodedescription Commands for functions and similar entities.
@subsection Functions and Similar Entities

@cindex Function definitions
@cindex Command definitions
@cindex Macro definitions, programming-language

This section describes the commands for describing functions and similar
entities with simple arguments:

@table @code
@findex deffn
@item @@deffn @var{category} @var{name} @var{arguments}@dots{}
The @code{@@deffn} command is the general definition command for
functions, interactive commands, and similar entities that may take
simple arguments.  You must choose a term to describe the category of entity
being defined; for example, ``Function'' could be used if the entity is
a function.  The @code{@@deffn} command is written at the beginning of a
line and is followed on the same line by the category of entity being
described, the name of this particular entity, and its arguments, if
any.  Terminate the definition with @code{@@end deffn} on a line of its
own.

@need 750
For example, here is a definition:

@example
@group
@@deffn Command forward-char nchars
Move point forward @@var@{nchars@} characters.
@@end deffn
@end group
@end example

@noindent
This shows a rather terse definition for a ``command'' named
@code{forward-char} with one argument, @var{nchars}.

@ignore
@c do not be specific about font differences between @deffn/@deftypefn
@c as this might change in the future
Where the output format allows, @code{@@deffn} uses a typewriter font
for @var{name}, and a slanted font for the rest of the @var{arguments},
as would be produced by @code{@@var}.
@end ignore

Within the text of the description, write an argument name
explicitly with @code{@@var} to refer to the value of the argument.
In the example above, we used @samp{@@var@{nchars@}} in this way.

In the extremely unusual case when an argument name contains
@samp{--}, or another character sequence which is treated specially
(@pxref{Conventions}), use @code{@@code} around the special
characters.  This avoids the conversion to typographic en-dashes and
em-dashes.
@c @var also works; that's what we used to recommend.

@findex defun
@item @@defun @var{name} @var{arguments}@dots{}
The @code{@@defun} command is the definition command for functions
with simple arguments.  @code{@@defun} is equivalent to
@samp{@@deffn Function @dots{}}.  Terminate the definition with
@code{@@end defun} on a line of its own.

@findex defmac
@item @@defmac @var{name} @var{arguments}@dots{}
The @code{@@defmac} command is the definition command for macros.
@code{@@defmac} is equivalent to @samp{@@deffn Macro @dots{}} and
works like @code{@@defun}.

@findex defspec
@item @@defspec @var{name} @var{arguments}@dots{}
The @code{@@defspec} command is the definition command for special
forms.  (In Lisp, a special form is an entity much like a function;
@pxref{Special Forms,,, elisp, GNU Emacs Lisp Reference Manual}.)
@code{@@defspec} is equivalent to @samp{@@deffn @{Special Form@}
@dots{}} and works like @code{@@defun}.
@end table

All these commands create entries in the index of functions.


@node Typed Functions
@nodedescription Commands for functions in typed languages.
@subsection Functions in Typed Languages

@cindex Typed functions
@cindex Functions, in typed languages

The @code{@@deftypefn} command and its variants are generic commands
for describing functions.  They are particularly suitable for languages in
which you must declare types of variables and functions, such as C and C++.

@table @code
@findex deftypefn
@item @@deftypefn @var{category} @var{data-type} @var{name} @var{arguments}@dots{}
The @code{@@deftypefn} command is the general definition command for
functions and similar entities that may take arguments and that could
be typed.  The @code{@@deftypefn} command is written at the beginning of
a line and is followed on the same line by the category of entity
being described, information on the returned value, the name of this
particular entity, and its arguments, if any.

@need 800
@noindent
For example,

@example
@group
@@deftypefn @{Library Function@} int foobar @@
  (int @@var@{foo@}, float @@var@{bar@})
@dots{}
@@end deftypefn
@end group
@end example

produces:

@quotation
@deftypefn {Library Function} int foobar  (int @var{foo}, float @var{bar})
@dots{}
@end deftypefn
@end quotation

This means that @code{foobar} is a ``library function'' that returns an
@code{int}, and its arguments are @var{foo} (an @code{int}) and
@var{bar} (a @code{float}).  @samp{Library Function} has to be
enclosed in braces to make it a single argument.

When using @code{@@deftypefn} command and variations,
you should mark parameter names with
@code{@@var} to distinguish these from data type names, keywords, and
other parts of the literal syntax of the programming language.
@ignore
@c do not be specific about font differences between @deffn/@deftypefn
@c as this might change in the future
Where the output format allows,
all output on the definition line is in a typewriter font by default.
@code{@@var} uses an appropriate font where it occurs.
@end ignore

If you are describing a procedure in a language that has packages,
such as Ada, you might consider using @code{@@deftypefn} in the
following manner:

@example
@group
@@deftypefn stacks private push @@
       (@@var@{s@}:in out stack; @@
       @@var@{n@}:in integer)
@dots{}
@@end deftypefn
@end group
@end example

@noindent
(In these examples the @code{@@deftypefn} arguments are shown using
continuations (@pxref{Def Cmd Continuation Lines}), but could be on a
single line.)

In this instance, the procedure is classified as belonging to the
package @code{stacks} rather than classified as a `procedure' and its
data type is described as @code{private}.  (The name of the procedure
is @code{push}, and its arguments are @var{s} and @var{n}.)  Output:

@deftypefn stacks private push @
       (@var{s}:in out stack; @
       @var{n}:in integer)
@dots{}
@end deftypefn

@code{@@deftypefn} and variants could be used when it is convenient to
interpret the arguments list as literal computer code, marking
argument names with @code{@@var}.
It is not necessary for any type names to appear,
and you can give an empty return type as @samp{@{@}}.

@ignore
@c This example is flawed because @var uppercases in Info output,
@c which is inappropriate for named arguments
For example, for documenting the R language, you could use input like

@example
@@deftypefn stats @{@} t.test (@@var@{x@}, @@var@{y@} = NULL,@@
  @@w@{@@var@{alternative@} = c("two.sided", "less", "greater")@},@@
  @@w@{@@var@{mu@} = 0@}, @@w@{@@var@{paired@} = FALSE@},@@
  @@w@{@@var@{var.equal@} = FALSE@},@@
  @@w@{@@var@{conf.level@} = 0.95@}, @@dots@{@})
@dots{}
@@end deftypefn
@end example

@noindent to get output like

@deftypefn stats {} t.test (@var{x}, @var{y} = NULL,@
  @w{@var{alternative} = c("two.sided", "less", "greater")},@
  @w{@var{mu} = 0}, @w{@var{paired} = FALSE},@
  @w{@var{var.equal} = FALSE},@
  @w{@var{conf.level} = 0.95}, @dots{})
@dots{}
@end deftypefn

@noindent Here the @code{@@w} command is used to prevent some line breaks.

@end ignore

The information on return values may be used to name the return
variables. For example, in Perl, returned scalars may be given the
@var{$result} and @var{$status} name in the following manner:

@example
@@deftypefn @{Sub@} @{(@@var@{$result@}, @@var@{$status@}) =@} @@
                     process (@@var@{$input@})
@dots{} Set @@var@{$status@} to 0 in case of failure @dots{}
@@end deftypefn
@end example

to get output like

@deftypefn {Sub} {(@var{$result}, @var{$status}) =} process (@var{$input})
@dots{} Set @var{$status} to 0 in case of failure @dots{}
@end deftypefn

@code{@@deftypefn} creates an entry in the index of functions for
@var{name}.

@findex deftypefun
@item @@deftypefun @var{data-type} @var{name} @var{arguments}@dots{}
The @code{@@deftypefun} command is the specialized definition command
for functions.  The command is equivalent to @samp{@@deftypefn Function
@dots{}}.

@code{@@deftypefun} creates an entry in the index of functions for
@var{name}.

@end table

@cindex Return type, own line for
@findex deftypefnnewline
Ordinarily, the return type is printed on the same line as the
function name and arguments, as shown above.  In source code, GNU
style for typed functions is to put the return type on a line by itself.
So Texinfo provides an option to do that: @code{@@deftypefnnewline on}.

This affects the generic functions only---not untyped functions with
simple arguments such as @code{@@deffn}, not typed
variables, etc.  Specifically, it affects the commands in this
section, and the analogous commands for object-oriented languages,
namely @code{@@deftypeop} and @code{@@deftypemethod}
(@pxref{Object-Oriented Methods}).

Specifying @code{@@deftypefnnewline off} reverts to the default.


@node Variables Commands
@nodedescription Commands for variables and similar entities.
@subsection Variables and Similar Entities

Here are the commands for defining variables and similar
entities:

@table @code
@findex defvr
@item @@defvr @var{category} @var{name}
The @code{@@defvr} command is a general definition command for
something like a variable---an entity that records a value.  You must
choose a term to describe the category of entity being defined; for
example, ``Variable'' could be used if the entity is a variable.
Write the @code{@@defvr} command at the beginning of a line and
follow it on the same line by the category of the entity and the
name of the entity.

We recommend capitalizing the category name like a title.  If the name
of the category contains spaces, as in the name ``User Option'',
enclose it in braces.  Otherwise, the second word will be mistaken for
the name of the entity.  For example,

@example
@group
@@defvr @{User Option@} fill-column
This buffer-local variable specifies
the maximum width of filled lines.
@dots{}
@@end defvr
@end group
@end example

Terminate the definition with @code{@@end defvr} on a line of its
own.

@code{@@defvr} creates an entry in the index of variables for @var{name}.

@findex defvar
@item @@defvar @var{name}
The @code{@@defvar} command is the definition command for variables.
@code{@@defvar} is equivalent to @samp{@@defvr Variable
@dots{}}.

@need 750
For example:

@example
@group
@@defvar kill-ring
@dots{}
@@end defvar
@end group
@end example

@code{@@defvar} creates an entry in the index of variables for
@var{name}.

@findex defopt
@cindex User options, marking
@item @@defopt @var{name}
The @code{@@defopt} command is the definition command for @dfn{user
options}, i.e., variables intended for users to change according to
taste; Emacs has many such (@pxref{Variables,,, emacs, The GNU Emacs
Manual}).  @code{@@defopt} is equivalent to @samp{@@defvr @{User
Option@} @dots{}}.
@end table


@node Typed Variables
@nodedescription Commands for variables in typed languages.
@subsection Variables in Typed Languages

@cindex Typed variables
@cindex Variables, in typed languages

Variables in typed languages are handled in a manner similar to
functions in typed languages.  @xref{Typed Functions}.  The general
definition command @code{@@deftypevr} corresponds to
@code{@@deftypefn} and the specialized definition command
@code{@@deftypevar} corresponds to @code{@@deftypefun}.

@table @code
@findex deftypevr
@item @@deftypevr @var{category} @var{data-type} @var{name}
The @code{@@deftypevr} command is the general definition command for
something like a variable in a typed language---an entity that records
a value.  You must choose a term to describe the category of the
entity being defined; for example, ``Variable'' could be used if the
entity is a variable.

The @code{@@deftypevr} command is written at the beginning of a line
and is followed on the same line by the category of the entity
being described, the data type, and the name of this particular
entity.

@need 800
@noindent
For example:

@example
@group
@@deftypevr @{Global Flag@} int enable
@dots{}
@@end deftypevr
@end group
@end example

@noindent
produces the following:

@quotation
@deftypevr {Global Flag} int enable
@dots{}
@end deftypevr
@end quotation

@findex deftypevar
@item @@deftypevar @var{data-type} @var{name}
The @code{@@deftypevar} command is the specialized definition command
for variables in typed languages.  @code{@@deftypevar} is equivalent
to @samp{@@deftypevr Variable @dots{}}.
@end table

These commands create entries in the index of variables.


@node Data Types
@nodedescription The definition command for data types.
@subsection Data Types

Here is the command for data types:

@table @code
@findex deftp
@item @@deftp @var{category} @var{name} @var{attributes}@dots{}
The @code{@@deftp} command is the generic definition command for data
types.  The command is written at the beginning of a line and is
followed on the same line by the category, by the name of the type
(which is a word like @code{int} or @code{float}), and then by names of
attributes of objects of that type.  Thus, you could use this command
for describing @code{int} or @code{float}, in which case you could use
@code{data type} as the category.  (A data type is a category of
certain objects for purposes of deciding which operations can be
performed on them.)

In Lisp, for example,  @dfn{pair} names a particular data
type, and an object of that type has two slots called the
@sc{car} and the @sc{cdr}.  Here is how you would write the first line
of a definition of @code{pair}.

@example
@group
@@deftp @{Data type@} pair car cdr
@dots{}
@@end deftp
@end group
@end example

@code{@@deftp} creates an entry in the index of data types.
@end table


@node Abstract Objects
@nodedescription Commands for object-oriented programming.
@subsection Object-Oriented Programming

@cindex Object-oriented programming

Here are the commands for formatting descriptions about abstract
objects, such as are used in object-oriented programming.  A class is
a defined type of abstract object.  An instance of a class is a
particular object that has the type of the class.  An instance
variable is a variable that belongs to the class but for which each
instance has its own value.

@menu
* Variables: Object-Oriented Variables.
* Methods:   Object-Oriented Methods.
@end menu


@node Object-Oriented Variables
@subsubsection Object-Oriented Variables

@cindex Variables, object-oriented

These commands allow you to define different sorts of variables in
object-oriented programming languages.

@table @code
@findex defcv
@item @@defcv @var{category} @var{class} @var{name}
The @code{@@defcv} command is the general definition command for
variables associated with classes in object-oriented programming.  The
@code{@@defcv} command is followed by three arguments: the category of
thing being defined, the class to which it belongs, and its
name.  For instance:

@example
@group
@@defcv @{Class Option@} Window border-pattern
@dots{}
@@end defcv
@end group
@end example

@noindent produces:
@defcv {Class Option} Window border-pattern
@dots{}
@end defcv

@code{@@defcv} creates an entry in the index of variables.

@findex deftypecv
@item @@deftypecv @var{category} @var{class} @var{data-type} @var{name}
The @code{@@deftypecv} command is the definition command for typed
class variables in object-oriented programming.  It is analogous to
@code{@@defcv} with the addition of the @var{data-type} parameter to
specify the type of the instance variable.

@example
@group
@@deftypecv @{Class Option@} Window int border-pattern
@dots{}
@@end deftypecv
@end group
@end example

@noindent produces:

@deftypecv {Class Option} Window int border-pattern
@dots{}
@end deftypecv

@code{@@deftypecv} creates an entry in the index of variables.

@findex defivar
@item @@defivar @var{class} @var{name}
The @code{@@defivar} command is the definition command for instance
variables in object-oriented programming.  @code{@@defivar} is
equivalent to @samp{@@defcv @{Instance Variable@} @dots{}}.  For
instance:

@example
@group
@@defivar Window border-pattern
@dots{}
@@end defivar
@end group
@end example

@noindent produces:

@defivar Window border-pattern
@dots{}
@end defivar

@code{@@defivar} creates an entry in the index of variables.

@findex deftypeivar
@item @@deftypeivar @var{class} @var{data-type} @var{name}
The @code{@@deftypeivar} command is the definition command for typed
instance variables in object-oriented programming.  It is analogous to
@code{@@defivar} with the addition of the @var{data-type} parameter to
specify the type of the instance variable.

@example
@group
@@deftypeivar Window int border-pattern
@dots{}
@@end deftypeivar
@end group
@end example

@noindent produces:

@deftypeivar Window @code{int} border-pattern
@dots{}
@end deftypeivar

@code{@@deftypeivar} creates an entry in the index of variables.

@end table


@node Object-Oriented Methods
@subsubsection Object-Oriented Methods

@cindex Methods, object-oriented

These commands allow you to define different sorts of function-like
entities resembling methods in object-oriented programming languages.
These entities take arguments, as functions do, but are associated with
particular classes of objects.

@table @code

@findex defop
@item @@defop @var{category} @var{class} @var{name} @var{arguments}@dots{}
The @code{@@defop} command is the definition command for these
method-like entities with simple arguments.

For example, some systems have constructs called @dfn{wrappers} that
are associated with classes as methods are, but that act more like
macros than like functions.  You could use @code{@@defop Wrapper} to
describe one of these.

Sometimes it is useful to distinguish methods and @dfn{operations}.
You can think of an operation as the specification for a method.
Thus, a window system might specify that all window classes have a
method named @code{expose}; we would say that this window system
defines an @code{expose} operation on windows in general.  Typically,
the operation has a name and also specifies the pattern of arguments;
all methods that implement the operation must accept the same
arguments, since applications that use the operation do so without
knowing which method will implement it.

Often it makes more sense to document operations than methods.  For
example, window application developers need to know about the
@code{expose} operation, but need not be concerned with whether a
given class of windows has its own method to implement this operation.
To describe this operation, you would write:

@example
@@defop Operation windows expose
@end example

The @code{@@defop} command is written at the beginning of a line and
is followed on the same line by the overall name of the category of
operation, the name of the class of the operation, the name of the
operation, and its arguments, if any.

@code{@@defop} creates an entry, such as `@code{expose} on
@code{windows}', in the index of functions.

@findex deftypeop
@item @@deftypeop @var{category} @var{class} @var{data-type} @var{name} @var{arguments}@dots{}
The @code{@@deftypeop} command is the generic definition command for
operations in object-oriented programming.  It is particularly suitable
for typed object-oriented languages. It is similar to
@code{@@defop} with the addition of the @var{data-type} parameter to
specify information on the return value of the method, for example the
return type.

@findex defmethod
@item @@defmethod @var{class} @var{name} @var{arguments}@dots{}
The @code{@@defmethod} command is the definition command for methods
in object-oriented programming.  A method is a kind of function that
implements an operation for a particular class of objects and its
subclasses.
@ignore
@c ADR: Who cares?!?
@c KB: Oh, I don't know, I think this info is crucial!
In the Lisp Machine, methods actually were functions, but
they were usually defined with @code{defmethod}.
@end ignore

@code{@@defmethod} is equivalent to @samp{@@defop Method @dots{}}.
The command is written at the beginning of a line and is followed by
the name of the class of the method, the name of the method, and its
arguments, if any.

@noindent
For example:
@example
@group
@@defmethod @code{bar-class} bar-method argument
@dots{}
@@end defmethod
@end group
@end example

@noindent
illustrates the definition for a method called @code{bar-method} of
the class @code{bar-class}.  The method takes an argument.

@code{@@defmethod} creates an entry in the index of functions.

@findex deftypemethod
@item @@deftypemethod @var{class} @var{data-type} @var{name} @var{arguments}@dots{}
The @code{@@deftypemethod} command is the definition command for methods
in object-oriented languages, in particular for typed languages
such as C++ and Java.  It is similar to the @code{@@defmethod} command
with the addition of the @var{data-type} parameter to specify information
on the return value of the method, for example the return type.

@end table

The commands with information on return values are affected by the
@code{@@deftypefnnewline} option (@pxref{Typed Functions,, Functions
in Typed Languages}).


@node Generic Definition Commands
@nodedescription Without automatic index entries.
@section Generic Definition Commands

Texinfo provides commands for definitions that do not produce automatic
index entries.

@findex defblock
@findex defline
@findex deftypeline
You create a generic definition environment with @samp{@@defblock}
paired with @samp{@@end defblock}.  Within this environment, use a
@code{@@defline} or @code{@@deftypeline} line for each symbol you
document.  For example:

@example
@@defblock
@@defline Macro mac (arg1, arg2)
Description of mac.
@@deftypeline Builtin int foo (int @@var@{bar@})
Description of foo.
@@end defblock
@end example

@noindent This produces the output:

@defblock
@defline Macro mac (arg1, arg2)
Description of mac.
@deftypeline Builtin int foo (int @var{bar})
Description of foo.
@end defblock

The syntax of @code{@@defline} is similar to that of @code{@@deffn}.
The first argument gives a category for the definition.  Follow this
with the symbol name, followed by any parameters.  You should surround
any arguments containing spaces with braces.

You use @code{@@deftypeline} in a similar way to @code{@@deftypefn},
following the category with a data type, and marking any parameters
with @code{@@var}. (@xref{Typed Functions}).)

To share the same description for multiple symbols, you can put several
@code{@@defline} lines together.  For example:

@example
@@defblock
@@defline Function set-var (value)
@@defline @{Settable Variable@} var
Description of set-var and var.
@@end defblock
@end example

@noindent This produces the output:

@defblock
@defline Function set-var (value)
@defline {Settable Variable} var
Description of set-var and var.
@end defblock

It may be useful to define line macros (@pxref{Line Macros}) in combination
with these commands.



@node Def Cmd Conventions
@nodedescription Conventions for writing definitions.
@section Conventions for Writing Definitions
@cindex Definition conventions
@cindex Conventions for writing definitions

A manual need not and should not contain more than one definition for
a given name.  An appendix containing a summary should use
@code{@@table} rather than the definition commands.

When you write a definition using @code{@@deffn}, @code{@@defun}, or
one of the other definition commands, please take care to use
arguments that indicate the meaning, as with the @var{count} argument
to the @code{forward-word} function.  Also, if the name of an argument
contains the name of a type, such as @var{integer}, take care that the
argument actually is of that type.

@emph{Fonts.}  As Texinfo is a semantic language, you should nearly never need
to specify font styles with explicit font commands in definitions
(@pxref{Fonts}).
However, you may be need to work around problems for particular
output formats and/or constructs.
Here are some possibilities:

@itemize @bullet
@item
Explicitly marking a Lisp keyword like @samp{&@var{keyword}} with
@code{@@r@{&keyword@}}, producing @r{&keyword}.

Note such keywords in definition arguments are (at present)
rendered in roman in @TeX{}, but this formatting is not done in
any other output format.

@item
@samp{@@r@{@@slanted@{argument@}@}},
producing @r{@slanted{argument}}, similar to @code{@@var}
but avoiding upper-casing its argument in Info output.

In this and the previous point, @code{@@r} resets the font from that
being used in the definition line context (slanted or typewriter) to
a roman, upright style.

@item
You could use @code{@@t} (or even @samp{@@r@{@@t@{@dots{}}, using @code{@@r}
to reset font styles) to mark literal syntax
on a definition line where
text would otherwise be output in the slanted roman style.
@code{@@code} would be inappropriate here as it adds quotation
marks in Info output.
@end itemize

Some degree of trial and error may be needed to get the result you
want.  As ever, how nested font commands combine depends on
the output format, so should be avoided where possible.

Hopefully, such usages are kept to a minimum.  One possibility is to
wrap these in @code{@@macro} (@pxref{Defining New Texinfo Commands}),
allowing these usages to be easily changed in the future.

@ignore
For example, if a metasyntactical symbol is needed and
is to be formatted as slanted code, and an strongly emphasized keyword is also
important for the language, the following could be used:

@example
@group
@@macro metasymbol @{argument@}
@@r@{@@t@{@@slanted@{\argument\@}@}@}
@@end macro

@@macro strongkeyword @{argument@}
@@r@{@@strong@{\argument\@}@}
@@end macro

@@defun fset arg @@metasymbol@{[ +@} @@strongkeyword@{*keyword@}
@dots{}
@@end defun
@end group
@end example

@noindent produces:

@macro metasymbol {argument}
@r{@t{@slanted{\argument\}}}
@end macro

@macro strongkeyword {argument}
@r{@strong{\argument\}}
@end macro

@defun fset arg @metasymbol{[ +} @strongkeyword{*keyword}
@dots{}
@end defun
@end ignore


@node Sample Function Definition
@nodedescription An example.
@section A Sample Function Definition
@cindex Sample function definition

Here is a definition from @ref{Calling Functions,,, elisp, The GNU Emacs
Lisp Reference Manual}, using the @code{@@defun} command.  The name of the
function, @code{apply}, follows immediately after the @code{@@defun}
command and it is followed, on the same line, by the parameter list.

@quotation
@defun apply function @r{&rest} arguments
@code{apply} calls @var{function} with @var{arguments}, just
like @code{funcall} but with one difference: the last of
@var{arguments} is a list of arguments to give to
@var{function}, rather than a single argument.  We also say
that this list is @dfn{appended} to the other arguments.

@code{apply} returns the result of calling @var{function}.
As with @code{funcall}, @var{function} must either be a Lisp
function or a primitive function; special forms and macros
do not make sense in @code{apply}.

@example
(setq f 'list)
    @result{} list
(apply f 'x 'y 'z)
@error{} Wrong type argument: listp, z
(apply '+ 1 2 '(3 4))
    @result{} 10
(apply '+ '(1 2 3 4))
    @result{} 10

(apply 'append '((a b c) nil (x y z) nil))
    @result{} (a b c x y z)
@end example

An interesting example of using @code{apply} is found in the description
of @code{mapcar}.
@end defun
@end quotation

In the Texinfo source file, this example should look like this:

@example
@group
@@defun apply function @@r@{&rest@} arguments
@@code@{apply@} calls @@var@{function@} with
@@var@{arguments@}, just like @@code@{funcall@} but with one
difference: the last of @@var@{arguments@} is a list of
arguments to give to @@var@{function@}, rather than a single
argument.  We also say that this list is @@dfn@{appended@}
to the other arguments.
@end group

@group
@@code@{apply@} returns the result of calling
@@var@{function@}.  As with @@code@{funcall@},
@@var@{function@} must either be a Lisp function or a
primitive function; special forms and macros do not make
sense in @@code@{apply@}.
@end group

@group
@@example
(setq f 'list)
    @@result@{@} list
(apply f 'x 'y 'z)
@@error@{@} Wrong type argument: listp, z
(apply '+ 1 2 '(3 4))
    @@result@{@} 10
(apply '+ '(1 2 3 4))
    @@result@{@} 10

(apply 'append '((a b c) nil (x y z) nil))
    @@result@{@} (a b c x y z)
@@end example
@end group

@group
An interesting example of using @@code@{apply@} is found
in the description of @@code@{mapcar@}.
@@end defun
@end group
@end example

@noindent
In this manual, this function is listed in the Command Index under
@code{apply}.


@node Internationalization
@nodedescription Supporting languages other than English.
@chapter Internationalization

@cindex Internationalization
Many Texinfo manuals are written in English because it is often used as
a common language in computer engineering in general, and in free software
projects in particular.  Texinfo, however, aims to support writing in any
language.  This area still needs work for @TeX{} to be able to support
any language.  More generally translations for strings output in documents are
missing for many languages and conventions for installation of manuals and
cross-references in multilingual environments are still unclear.  (If you are
the one helping to translate the fixed strings written to documents,
@pxref{Internationalization of Document Strings}.)

@cindex Locale, declaring
The current document locale is mainly determined by the main language and
optional country code, set by @code{@@documentlanguage}.  The document
@dfn{script} (also called alphabet) is set by @code{@@documentscript}.
For example the Serbian language is generally written in the Cyrillic alphabet,
but can also be written in the Latin alphabet.  Lastly language variants that
cannot be specified with the country code are set with
@code{@@documentlanguagevariant}.  These variants may correspond to dialects or
specific orthographies, among others.  @code{@@documentlanguagevariant} should
rarely be useful for technical documentation, but is needed in Texinfo to make
sure that all the languages can be specified.

For a list of the various accented and special characters that Texinfo
supports via @@-commands, see @ref{Inserting Accents}.


@node Setting the language
@nodedescription Declaring the current language.
@section Setting the language
@c old names
@anchor{documentlanguage}
@anchor{@code{@@documentlanguage}}

@findex documentlanguage
@cindex Language, declaring
@cindex Document language, declaring

The @code{@@documentlanguage} command declares the current document
main language.  Write it on a line by itself, near the beginning of the file.

@example
@@documentlanguage @var{ll}[_@var{CC}]
@end example

Include a two-letter (or three-letter) ISO@tie{}639 language code
(@var{ll}) following
the command name, optionally followed by an underscore and two-letter
ISO@tie{}3166 country code (@var{CC}).  If you have a
multilingual document, the intent is to be able to use this command
multiple times, to declare each language change.

As with GNU Gettext (@pxref{Top,,, gettext, Gettext}), if the country
code is omitted, the main dialect is assumed where possible.  For
example, @code{de} is equivalent to @code{de_DE} (German as spoken in
Germany).

The @code{@@documentlanguagevariant} command declares additional language
variants on top of the main language (and optional country code).  A list of
variants can be specified.  Write it on a line by itself, after
@code{@@documentlanguage}.

@findex documentlanguagevariant
@cindex Language variants, declaring

@example
@@documentlanguagevariant [@var{variant1}][, @var{variant2}][, @dots{}]
@end example

Include variants (@var{variant1}, optionally @var{variant2}, @dots{})
registered in the IANA language subtags registry, separated by commas,
following the command name.  An empty argument unsets the language variants.
Language variants should rarely be needed.  Their support also requires
associated translations, therefore specifying variants will not often have
a practical effect.

@findex documentscript
@cindex Language alphabet, declaring
@cindex Language script, declaring
@cindex Document language script, declaring

The @code{@@documentscript} command sets an alternative script.  Do not set the
script if the usual script for the language is used.  Write it on a line by
itself, after @code{@@documentlanguage}.

@example
@@documentscript [@var{script}]
@end example

Include a script name, either a four letter ISO@tie{}15924 script code name,
such as @samp{Latn} or a well-known alias, such as @samp{latin} or
@samp{cyrillic} following the command name.  An empty argument unsets the
script.

Setting @code{@@documentlanguage} unsets both language variants
and script.

@cindex Document strings, translation of
These commands change the translation of various @dfn{document strings}
such as ``see'' in cross-references (@pxref{Cross References}),
``Function'' in defuns (@pxref{Definition Commands}), and so on.
Optionally, @code{@@documentlanguage} and @code{@@documentscript} may also
affect how @command{texi2any} sorts indices (@pxref{Global Customization
Variables}, under @code{DOCUMENTLANGUAGE_COLLATION}).  If the document language
is not specified, the default English document strings are output as they are.

Note that in Info output, some strings, such as ``Node:'', ``Next:'',
``Menu:'', etc., are keywords and so are not translated.

In DocBook and HTML, the language at the end of the preamble set by
these commands determines the language specified in output file headers.
In DocBook output these commands also set or reset the language for
following sections.

For @LaTeX{}, these commands cause code to load the @samp{babel} package
to be output in the preamble, and @code{\selectlanguage} to be output.

@cindex @file{txi-@var{locale}.tex}
For @TeX{}, these commands cause a file @file{txi-@var{locale}.tex} to
be read (if it exists).  If @code{@@documentlanguage} argument
contains the optional @samp{_@var{CC}} suffix, this is tried first.
For example, with @code{@@documentlanguage de_DE}, @TeX{} first looks
for @file{txi-de_DE.tex}, then @file{txi-de.tex}.

Such a @file{txi-*} file is intended to redefine the various English
words used in @TeX{} output, such as `Chapter', `See', and so on.  We
are aware that individual words like these cannot always be translated
in isolation, and that a very different strategy would be required for
ideographic (among other) scripts.  Help in improving Texinfo's
language support is welcome.

@cindex Hyphenation patterns, language-dependent
@code{@@documentlanguage} and @code{@@documentscript} also change @TeX{}'s
current hyphenation patterns, if the @TeX{} program being run has the necessary
support included.  This will generally not be the case for @command{tex}
itself, but will usually be the case for up-to-date distributions of
the extended @TeX{} programs @command{etex} (DVI output) and
@command{pdftex} (PDF output).  @command{texi2dvi} will use the
extended @TeX{}s if they are available (@pxref{Format with
@command{texi2dvi}}).

@cindex ISO 639 language codes
@cindex ISO 3166 country codes
@cindex Language codes
@cindex Country codes
@cindex IANA language subtag registry
@cindex Language variants
@cindex Language script codes
@cindex ISO 15924 script codes
We use the IANA language subtag registry
@url{https://www.iana.org/assignments/language-subtag-registry} to get
the up-to-date list of ISO@tie{}639 languages, ISO@tie{}3166 country codes,
ISO@tie{}15924 script code names and language variants names.


@node @code{@@documentencoding}
@nodedescription Declaring the input encoding.
@section @code{@@documentencoding @var{enc}}: Set Input Encoding

@anchor{documentencoding}@c old name
@findex documentencoding
@cindex Encoding, declaring
@cindex Input encoding, declaring
@cindex Character set, declaring
@cindex Document input encoding

By default, the input and output document encoding are assumed
to be UTF-8, the vast global character encoding, expressed in 8-bit bytes.
UTF-8 is compatible with 7-bit ASCII.  It is recommended to use UTF-8
encoding for Texinfo manuals.

The @code{@@documentencoding} command declares the input document encoding,
and also affects the encoding of the output.  Write it on a line by itself,
with a valid encoding specification following, near the beginning of the file
if your document encoding is not the default encoding.

@example
@@documentencoding @var{enc}
@end example

UTF-8 should always be the best choice for the encoding.
Texinfo still supports additional encodings, mainly for compatibility with
older manuals@footnote{@command{texi2any} supports more encodings for Texinfo
manuals, potentially all the encodings supported by both Perl and iconv
(@pxref{Generic Charset Conversion,,, libc, The GNU C Library}).
The support in output formats may be lacking, however, especially for @LaTeX{}
output.}:

@table @code
@item US-ASCII
Character encoding based on the English alphabet.

@cindex Euro symbol, and encodings
@item ISO-8859-1
@itemx ISO-8859-15
@itemx ISO-8859-2
These specify the pre-UTF-8 standard encodings for Western European
(the first two) and Eastern European languages (the third), respectively.
ISO 8859-15 replaces some little-used characters from 8859-1 (e.g.,
precomposed fractions) with more commonly needed ones, such as the
Euro symbol (@euro{}).

A full description of the encodings is beyond our scope here;
one useful reference is @uref{http://czyborra.com/charsets/iso8859.html}.

@item koi8-r
This was a commonly used encoding for the Russian language before UTF-8.

@item koi8-u
This was a commonly used encoding for the Ukrainian language before UTF-8.

@end table

@cindex Local Variables section, for encoding
@cindex Info output, and encoding
In Info output, a so-called `Local Variables' section (@pxref{File
Variables,,, emacs, The GNU Emacs Manual}) is output including
the output encoding.  This allows Info readers to set the encoding
appropriately.  It looks like this:

@example
Local Variables:
coding: UTF-8
End:
@end example

By default, for Info and plain text output, @command{texi2any} outputs
accent constructs and special characters (such as @code{@@'e})
as the actual UTF-8 sequence or 8-bit character in the output
encoding where possible.  If this is not possible, or if the option
@option{--disable-encoding} is given, an ASCII transliteration is
used instead.

@cindex HTML output @subentry encodings
@cindex @code{http-equiv}, and charset specification
@cindex @code{<meta>} HTML tag, and charset specification
In HTML output, a @samp{<meta>} tag is output, in the @samp{<head>}
section of the HTML, that specifies the output encoding.  Web servers and
browsers cooperate to use this information so the correct encoding is
used to display the page, if supported by the system.  That looks like
this:

@example
<meta http-equiv="Content-Type" content="text/html;
     charset=utf-8">
@end example

In HTML and @LaTeX{} output, if @code{OUTPUT_CHARACTERS} is set
(@pxref{Customization Variables for Multiple Formats}), accent constructs and
special characters, such as @code{@@'e} or @code{``}, are output as the actual
UTF-8 sequence or 8-bit character in the output encoding where possible.
Otherwise, HTML entities are used for those characters in HTML, and @LaTeX{}
macros are used in @LaTeX{}.

In DocBook output, if the encoding is different from UTF-8,
an @code{encoding} attribute is added to the XML declaration.  If
@code{OUTPUT_CHARACTERS} is set (@pxref{Customization Variables for Multiple
Formats}), accent constructs such as @code{@@'e} are output as the actual 8-bit
or UTF-8 character in the output encoding where possible.  Otherwise XML
entities are used for those constructs.

@cindex Computer Modern fonts
In @TeX{} output, the characters which are supported in the standard
Computer Modern fonts are output accordingly.  For example, this
means using constructed accents rather than precomposed glyphs.
Using a missing character generates a warning message, as does
specifying an unimplemented encoding.

Although modern @TeX{} systems support nearly every script in use in
the world, this wide-ranging support is not available in
@file{texinfo.tex}, and it's not feasible to duplicate or incorporate
all that effort.

In @LaTeX{} output, code loading the @samp{inputenc} package is output
based on the encoding.  This, by itself, does not ensures that all
the characters from the input document  can be subsequently output.
The fonts used in the default case should cover the specific Texinfo
glyphs, but not all the possible encoded characters.  You may need to
load different fonts in the preamble and use
@code{\DeclareUnicodeCharacter} with a UTF-8 encoding.  For example:
@example
@@latex
\DeclareUnicodeCharacter@{017B@}@{\.Z@}
@@end latex
@end example

Cross-references between Info files in different character encodings
with non-ASCII characters in node names fail.  We strongly recommend
using UTF-8 only as the encoding for manuals with non-ASCII characters
in the destinations of cross-references.


@node Conditionals
@nodedescription Specifying text for only some output cases.
@chapter Conditionally Visible Text
@cindex Conditionally visible text
@cindex Text, conditionally visible
@cindex Visibility of conditional text
@cindex If text conditionally visible

The @dfn{conditional commands} allow you to use different text for
different output formats, or for general conditions that you define.
For example, you can use them to specify different text for the
printed manual and the Info output.

The conditional commands comprise the following categories.

@itemize @bullet
@item
Commands specific to an output format (Info, @TeX{}, HTML, @dots{}).

@item
Commands specific to any output format @emph{excluding} a given
one (e.g., not Info, not @TeX{}, @dots{}).

@item
`Raw' formatter text for any output format, passed straight
through with minimal (but not zero) interpretation of @@-commands.

@item
Format-independent variable substitutions, and testing if a variable
is set or clear.

@end itemize


@node Conditional Commands
@nodedescription Text for a given format.
@section Conditional Commands

Texinfo has an @code{@@if@var{format}} environment for each output
format, to allow conditional inclusion of text for a particular output
format.

@findex ifinfo
@code{@@ifinfo} begins segments of text that should be ignored when
not producing Info output, in particular in printed output.  The
segment of text appears only in the Info file and, for historical
compatibility, the plain text output.

@findex ifdocbook
@findex ifepub
@findex ifhtml
@findex iflatex
@findex ifplaintext
@findex iftex
The environments for the other formats are analogous:

@table @code
@item @@ifdocbook @dots{} @@end ifdocbook
Text to appear only in the DocBook output.

@item @@ifepub @dots{} @@end ifepub
Text to appear only in the EPUB output.

@item @@ifhtml @dots{} @@end ifhtml
Text to appear only in the HTML and EPUB output.

@item @@iflatex @dots{} @@end iflatex
Text to appear only in the @LaTeX{} output.

@item @@ifplaintext @dots{} @@end ifplaintext
Text to appear only in the plain text output.

@item @@iftex @dots{} @@end iftex
Text to appear only in the printed manual.
@end table

The @code{@@if@dots{}} and @code{@@end if@dots{}} commands must appear
on lines by themselves in your source file.  The newlines following
the commands are (more or less) treated as whitespace, so that the
conditional text is flowed normally into a surrounding paragraph.

The @code{@@if@dots{}} constructs are intended to conditionalize
normal Texinfo source; @pxref{Raw Formatter Commands}, for using
underlying format commands directly.

Here is an example showing all these conditionals:

@example
@@iftex
This text will appear only in the printed manual.
@@end iftex
@@ifinfo
However, this text will appear only in Info and plain text.
@@end ifinfo
@@ifhtml
And this text will only appear in HTML (and in EPUB).
@@end ifhtml
@@iflatex
Moreover, this text will only appear in @@LaTeX@{@}.
@@end iflatex
@@ifplaintext
Whereas this text will only appear in plain text.
@@end ifplaintext
@@ifdocbook
Nevertheless, this will only appear in DocBook.
@@end ifdocbook
@end example

@noindent
The preceding example produces the following line:

@iftex
This text will appear only in the printed manual.
@end iftex
@ifinfo
However, this text will appear only in Info and plain text.
@end ifinfo
@ifhtml
And this text will only appear in HTML (and in EPUB).
@end ifhtml
@iflatex
Moreover, this text will only appear in @LaTeX{}.
@end iflatex
@ifplaintext
Whereas this text will only appear in plain text.
@end ifplaintext
@ifdocbook
Nevertheless, this will only appear in DocBook.
@end ifdocbook

@noindent
Notice that you only see one of the input lines, depending on which
version of the manual you are reading.

@findex errormsg
In complex documents, you may want Texinfo to issue an error message
in some conditionals that should not ever be processed.  The
@code{@@errormsg@{@var{text}@}} command will do this; it takes one
argument, the text of the error message.

We mention @code{@@errormsg@{@}} here even though it is not strictly
related to conditionals, since in practice it is most likely to be
useful in that context.  Technically, it can be used anywhere.
@xref{External Macro Processors}, for a caveat regarding the line
numbers which @code{@@errormsg} emits in @TeX{}.

@findex ifxml
Conditionals for removed formats are still recognized for a while before being
removed.  The associated text is always ignored.  For example, the
@code{@@ifxml} environment begins segments of text that are ignored in all the
output formats.  This command will stop being recognized in a future release.


@node Conditional Not Commands
@nodedescription Text for any format other than a given one.
@section Conditional Not Commands
@findex ifnotdocbook
@findex ifnotepub
@findex ifnothtml
@findex ifnotinfo
@findex ifnotlatex
@findex ifnotplaintext
@findex ifnottex

You can specify text to be included in any output format @emph{other}
than a given one with the @code{@@ifnot@dots{}} environments:

@example
@@ifnotdocbook @dots{} @@end ifnotdocbook
@@ifnotepub @dots{} @@end ifnotepub
@@ifnothtml @dots{} @@end ifnothtml
@@ifnotinfo @dots{} @@end ifnotinfo
@@ifnotlatex @dots{} @@end ifnotlatex
@@ifnotplaintext @dots{} @@end ifnotplaintext
@@ifnottex @dots{} @@end ifnottex
@end example

@noindent
The @code{@@ifnot@dots{}} command and the @code{@@end} command must
appear on lines by themselves in your actual source file.

If the output file is being made in the given format, the
region is @emph{ignored}.  Otherwise, it is included.

There is one exception (for historical compatibility):
@code{@@ifnotinfo} text is omitted for both Info and plain text
output, not just Info.  To specify text which appears only in Info and
not in plain text, use @code{@@ifnotplaintext}, like this:

@example
@@ifinfo
@@ifnotplaintext
This will be in Info, but not plain text.
@@end ifnotplaintext
@@end ifinfo
@end example

The regions delimited by these commands are ordinary Texinfo source as
with @code{@@iftex}, not raw formatter source as with @code{@@tex}
(@pxref{Raw Formatter Commands}).

@findex ifnotxml
Conditionals for removed formats, such as @code{@@ifnotxml} are
never omitted and stop being recognized after a while.


@node Raw Formatter Commands
@nodedescription Using raw formatter commands.
@section Raw Formatter Commands
@cindex Raw formatter commands

@cindex @TeX{} commands, using ordinary
@cindex Ordinary @TeX{} commands, using
@cindex Commands using raw @TeX{}
@cindex Plain @TeX{}

The @code{@@if@dots{}} conditionals just described must be used only
with normal Texinfo source.  For instance, most features of plain
@TeX{} will not work within @code{@@iftex}.  The purpose of
@code{@@if@dots{}} is to provide conditional processing for Texinfo
source, not provide access to underlying formatting features.  For
that, Texinfo provides so-called @dfn{raw formatter commands}.  They
should only be used when truly required (most documents do not need
them).

@findex tex
@cindex Category codes, of plain @TeX{}
The first raw formatter command is @code{@@tex}.  You can enter plain
@TeX{} completely, and use @samp{\} in the @TeX{} commands, by
delineating a region with the @code{@@tex} and @code{@@end tex}
commands.  All plain @TeX{} commands and category codes are restored
within a @code{@@tex} region.  The sole exception is that the
@code{@@} character still introduces a command, so that @code{@@end
tex} can be recognized.  Texinfo processors will not output material
in such a region unless @TeX{} output is being produced.

@findex \gdef @r{within @code{@@tex}}
@findex \globaldefs @r{within @code{@@tex}}
In complex cases, you may wish to define new @TeX{} macros within
@code{@@tex}.  You must use @code{\gdef} to do this, not @code{\def},
because @code{@@tex} regions are processed in a @TeX{} group.  If you
need to make several definitions, you may wish to set
@code{\globaldefs=1} (its value will be restored to zero as usual when
the group ends at @code{@@end tex}, so it won't cause problems with
the rest of the document).

@cindex Equation, displayed, in plain @TeX{}
@cindex Displayed equation, in plain @TeX{}
As an example, here is a displayed equation written in plain @TeX{}:

@example
@@tex
$$ \chi^2 = \sum_@{i=1@}^N
         \left (y_i - (a + b x_i)
         \over \sigma_i\right)^2 $$
@@end tex
@end example

@noindent
The output of this example will appear only in a printed manual.  If
you are reading this in a format not generated by @TeX{}, you will not
see the equation that appears in the printed manual.

@tex
$$ \chi^2 = \sum_{i=1}^N
         \left(y_i - (a + b x_i)
         \over \sigma_i\right)^2 $$
@end tex

@cindex HTML, including raw
@cindex EPUB, including raw
@findex html
@cindex DocBook, including raw
@findex docbook
@cindex @LaTeX{}, including raw
@findex latex
Analogously, you can use @code{@@html @dots{} @@end html} for a region of
raw HTML (or raw EPUB), @code{@@docbook @dots{} @@end docbook} for a
region of raw DocBook, @code{@@latex @dots{} @@end latex} for a
region of raw @LaTeX{}.

The behavior of newlines in raw regions is unspecified.

In all cases, in raw processing, @code{@@} retains the same meaning as
in the remainder of the document.  Thus, the Texinfo processors must
recognize and even execute, to some extent, the contents of the raw
regions, regardless of the final output format.  Therefore, specifying
changes that globally affect the document inside a raw region leads to
unpredictable and generally undesirable behavior.  For example, using
the @code{@@kbdinputstyle} command inside a raw region is undefined.
The remedy is simple: don't do that.

Most of the output generated for EPUB is actually HTML, therefore there is no
similar command for raw EPUB.  In @code{@@documentinfo}, you can provide EPUB
metadata for the whole EPUB document.  When outputting EPUB, @code{@@html} in
@code{@@documentinfo} is not output as HTML metadata in HTML files output as
part of conversion to EPUB, but as EPUB specific metadata.

In the following example, the EPUB markup in the first @code{@@html} block is
output as EPUB specific metadata when outputting EPUB.  In that situation, it
is not possible to add metadata to HTML output as part of the conversion to
EPUB.  When outputting HTML, the second @code{@@html} block is added to the
HTML header instead:

@example
@@documentinfo
@@ifepub
@@html
<dc:creator id="creator">Some Body</dc:creator>
<meta refines="#creator" property="role" scheme="marc:relators"
    id="role">aut</meta>
@@end html
@@end ifepub
@@ifnotepub
@@html
<meta name="creator" content="Some Body" />
@@end html
@@end ifnotepub
@@end documentinfo
@end example

@findex xml
Removed formats raw regions commands such as @code{@@xml} are recognized
for a while.  Removed formats raw regions are ignored.


@node Inline Conditionals
@nodedescription Brace-delimited conditional text.
@section Inline Conditionals: @code{@@inline}, @code{@@inlineifelse}, @code{@@inlineraw}
@findex inlinefmt
@findex inlinefmtifelse
@findex inlineraw
@cindex Inline conditionals
@cindex Conditional commands, inline
@cindex Brace-delimited conditional text
@cindex Newlines, avoiding in conditionals
@cindex Whitespace, controlling in conditionals

Texinfo provides a set of conditional commands with arguments given
within braces:

@table @code
@item @@inlinefmt@{@var{format}, @var{text}@}
Process the Texinfo @var{text} if @var{format} output is being
generated.

@item @@inlinefmtifelse@{@var{format}, @var{then-text}, @var{else-text}@}
Process the Texinfo @var{then-text} if @var{format} output is being
generated; otherwise, process @var{else-text}.

@item @@inlineraw@{@var{format}, @var{text}@}
Similar, but for raw @var{text} (@pxref{Raw Formatter Commands}).
@end table

The supported @var{format} names are:

@example
docbook  epub  html  info  latex  plaintext  tex
@end example

For example,

@example
@@inlinefmt@{html, @@emph@{HTML-only text@}@}
@end example

@noindent is nearly equivalent to

@example
@@ifhtml
@@emph@{HTML-only text@}
@@end ifhtml
@end example

@noindent except that no whitespace is added, as happens in the latter
(environment) case.

In these commands, whitespace is ignored after the comma separating
the arguments, as usual, but is @emph{not} ignored at the end of
@var{text}.

To insert a literal at sign, left brace, or right brace in one of the
arguments, you must use the alphabetic commands @code{@@atchar@{@}}
(@pxref{Inserting an Atsign}), and @code{@@lbracechar@{@}} or
@code{@@rbracechar@{@}} (@pxref{Inserting Braces}), or the parsing
will become confused.

With @code{@@inlinefmtifelse}, it is also necessary to use
@code{@@comma@{@}} to avoid mistaking a @samp{,} in the text for the
delimiter.  With @code{@@inlinefmt} and @code{@@inlineraw},
@code{@@comma@{@}} is not required (though it's fine to use it), since
these commands always have exactly two arguments.

For @TeX{}, the processed @var{text} cannot contain newline-delimited
commands.  Text to be ignored (i.e., for non-@TeX{}) can, though.

Two other @code{@@inline...} conditionals complement the
@code{@@ifset} and @code{@@ifclear} commands; see the next section.


@node @code{@@set @@clear @@value}
@nodedescription Variable tests and substitutions.
@section Flags: @code{@@set}, @code{@@clear}, conditionals, and @code{@@value}

@anchor{set clear value}@c old name
You can direct the Texinfo formatting commands to format or ignore parts
of a Texinfo file with the @code{@@set}, @code{@@clear}, @code{@@ifset},
and @code{@@ifclear} commands.  Here is a summary:

@table @code
@item @@set @var{flag} [@var{value}]
Set the variable @var{flag}, to the optional @var{value} if specified.

@item @@clear @var{flag}
Undefine the variable @var{flag}, whether or not it was previously defined.

@item @@ifset @var{flag}
If @var{flag} is set, text through the next @code{@@end ifset} command
is formatted.  If @var{flag} is clear, text through the following
@code{@@end ifset} command is ignored.

@item @@inlineifset@{@var{flag}, @var{text}@}
Brace-delimited version of @code{@@ifset}.

@item @@ifclear @var{flag}
If @var{flag} is set, text through the next @code{@@end ifclear} command
is ignored.  If @var{flag} is clear, text through the following
@code{@@end ifclear} command is formatted.

@item @@inlineifclear@{@var{flag}, @var{text}@}
Brace-delimited version of @code{@@ifclear}.

@end table


@node @code{@@set @@value}
@nodedescription Expand a flag variable to a string.
@subsection @code{@@set} and @code{@@value}

@anchor{set value}@c old name
@findex set
@findex value
@findex clear

You use the @code{@@set} command to specify a value for a flag, which
is later expanded by the @code{@@value} command.

A @dfn{flag} (aka @dfn{variable}) name is an identifier starting with
an alphanumeric, @samp{-}, or @samp{_}.  Subsequent characters, if
any, may not be whitespace, @samp{@@}, braces, angle brackets, or any
of @samp{~`^+|}; other characters, such as @samp{%}, may work.
However, it is best to use only letters and numerals in a flag name,
not @samp{-} or @samp{_} or others---they will work in some contexts,
but not all, due to limitations in @TeX{}.

The value is the remainder of the input line, and can contain anything.

@ignore
However, unlike most other commands which take the rest of the line as
a value, @code{@@set} need not appear at the beginning of a line.
@end ignore

Write the @code{@@set} command like this:

@example
@@set foo This is a string.
@end example

@noindent
This sets the value of the flag @code{foo} to ``This is a string.''.

The Texinfo processors then replace a @code{@@value@{@var{flag}@}}
command with the string to which @var{flag} is set.  Thus, when
@code{foo} is set as shown above, the Texinfo processors convert this:

@example
@group
@@value@{foo@}
@exdent @r{to this:}
This is a string.
@end group
@end example

You can write a @code{@@value} command within a paragraph; but you
must write a @code{@@set} command on a line of its own.

If you write the @code{@@set} command like this:

@example
@@set foo
@end example

@noindent
without specifying a string, the value of @code{foo} is the empty string.

If you clear a previously set flag with @code{@@clear @var{flag}}, a
subsequent @code{@@value@{flag@}} command will report an error.

For example, if you set @code{foo} as follows:

@example
@@set howmuch very, very, very
@end example

@noindent
then the processors transform

@example
@group
It is a @@value@{howmuch@} wet day.
@exdent @r{into}
It is a very, very, very wet day.
@end group
@end example

If you write

@example
@@clear howmuch
@end example

@noindent
then the processors transform

@example
@group
It is a @@value@{howmuch@} wet day.
@exdent @r{into}
It is a @{No value for "howmuch"@} wet day.
@end group
@end example

@code{@@value} cannot be reliably used as the argument to an accent
command (@pxref{Inserting Accents}).  For example, this fails:

@c This does not seems to fail with texi2any, but fails with TeX.
@example
@@set myletter a
@@'@@value@{myletter@}    @c fails!
@end example


@node @code{@@ifset @@ifclear}
@nodedescription Format a region if a flag is set.
@subsection @code{@@ifset} and @code{@@ifclear}

@anchor{ifset ifclear}@c old name
@findex ifset

When a @var{flag} is set, the Texinfo formatting commands format text
between subsequent pairs of @code{@@ifset @var{flag}} and @code{@@end
ifset} commands.  When the @var{flag} is cleared, the Texinfo formatting
commands do @emph{not} format the text.  @code{@@ifclear} operates
analogously.

Write the conditionally formatted text between @code{@@ifset @var{flag}}
and @code{@@end ifset} commands, like this:

@example
@group
@@ifset @var{flag}
@var{conditional-text}
@@end ifset
@end group
@end example

For example, you can create one document that has two variants, such as
a manual for a `large' and `small' model:

@cindex Shrubbery
@example
You can use this machine to dig up shrubs
without hurting them.

@@set large

@@ifset large
It can also dig up fully grown trees.
@@end ifset

Remember to replant promptly @dots{}
@end example

@noindent
In the example, the formatting commands will format the text between
@code{@@ifset large} and @code{@@end ifset} because the @code{large}
flag is set.

When @var{flag} is cleared, the Texinfo formatting commands do
@emph{not} format the text between @code{@@ifset @var{flag}} and
@code{@@end ifset}; that text is ignored and does not appear in the output.

For example, if you clear the flag of the preceding example by writing
an @code{@@clear large} command after the @code{@@set large} command
(but before the conditional text), then the Texinfo formatting commands
ignore the text between the @code{@@ifset large} and @code{@@end ifset}
commands.  In the formatted output, that text does not appear; you see
only the lines that say, ``You can use
this machine to dig up shrubs without hurting them.  Remember to replant
promptly @dots{}''.

@findex ifclear
If a flag is cleared with a @code{@@clear @var{flag}} command, then
the formatting commands format text between subsequent pairs of
@code{@@ifclear} and @code{@@end ifclear} commands.  But if the flag
is set with @code{@@set @var{flag}}, then the formatting commands do
@emph{not} format text between an @code{@@ifclear} and an @code{@@end
ifclear} command; rather, they ignore that text.  An @code{@@ifclear}
command looks like this:

@example
@@ifclear @var{flag}
@end example


@node @code{@@inlineifset @@inlineifclear}
@nodedescription Brace-delimited flag conditionals.
@subsection @code{@@inlineifset} and @code{@@inlineifclear}

@findex inlineifset
@findex inlineifclear
@cindex Flag conditionals, brace-delimited
@cindex Brace-delimited flag conditionals

@code{@@inlineifset} and @code{@@inlineifclear} provide
brace-delimited alternatives to the @code{@@ifset} and
@code{@@ifclear} forms, similar to the other @code{@@inline...}
Commands (@pxref{Inline Conditionals}).  The same caveats about
argument parsing given there apply here too.

@table @code
@item @@inlineifset@{@var{var}, @var{text}@}
Process the Texinfo @var{text} if the flag @var{var} is defined.

@item @@inlineifclear@{@var{var}, @var{text}@}
Process the Texinfo @var{text} if the flag @var{var} is not defined.
@end table

Except for the syntax, their general behavior and purposes is the same
as with @code{@@ifset} and @code{@@ifclear}, described in the previous
section.


@node @code{@@value} Example
@nodedescription An easy way to update edition information.
@subsection @code{@@value} Example

@anchor{value Example}@c old name

You can use the @code{@@value} command to minimize the number of
places you need to change when you record an update to a manual.
@xref{GNU Sample Texts}, for the full text of an example of using this
to work with Automake distributions.

This example is adapted from @ref{Top,,, make, The GNU Make Manual}.

@enumerate
@item
Set the flags:

@example
@group
@@set EDITION 0.35 Beta
@@set VERSION 3.63 Beta
@@set UPDATED 14 August 1992
@@set UPDATE-MONTH August 1992
@end group
@end example

@item
Write text for the @code{@@copying} section (@pxref{@code{@@copying}}):

@example
@group
@@copying
This is Edition @@value@{EDITION@},
last updated @@value@{UPDATED@},
of @@cite@{The GNU Make Manual@},
for @@code@{make@}, version @@value@{VERSION@}.

Copyright @dots{}

Permission is granted @dots{}
@@end copying
@end group
@end example

@item
Write text for the title page, for people reading the printed manual:

@example
@group
@@documentinfo
@@title GNU Make
@@subtitle A Program for Directing Recompilation
@@subtitle Edition @@value@{EDITION@}, @dots{}
@@subtitle @@value@{UPDATE-MONTH@}
@@end documentinfo
@end group
@end example

@noindent
(On a printed cover, a date listing the month and the year looks less
fussy than a date listing the day as well as the month and year.)

@item
Write text for the Top node, for people reading the Info file:

@example
@group
@@ifnottex
@@node Top
@@top Make

This is Edition @@value@{EDITION@},
last updated @@value@{UPDATED@},
of @@cite@{The GNU Make Manual@},
for @@code@{make@}, version @@value@{VERSION@}.
@@end ifnottex
@end group
@end example

After you format the manual, the @code{@@value} constructs have been
expanded, so the output contains text like this:

@example
@group
This is Edition 0.35 Beta, last updated 14 August 1992,
of `The GNU Make Manual', for `make', Version 3.63 Beta.
@end group
@end example
@end enumerate

When you update the manual, you change only the values of the flags; you
do not need to edit the three sections.


@node Testing for Texinfo Commands
@nodedescription Testing if a Texinfo command is available.
@section Testing for Texinfo Commands: @code{@@ifcommanddefined}, @code{@@ifcommandnotdefined}

@cindex Testing for Texinfo commands
@cindex Checking for Texinfo commands
@cindex Texinfo commands, testing for
@cindex Commands, testing for Texinfo
@cindex Versions of Texinfo, adapting to
@cindex Features of Texinfo, adapting to
@findex ifcommanddefined
@findex ifcommandnotdefined

Occasionally, you may want to arrange for your manual to test if a
given Texinfo command is available and (presumably) do some sort of
fallback formatting if not.  There are conditionals
@code{@@ifcommanddefined} and @code{@@ifcommandnotdefined} to do this.
For example:

@example
@@ifcommanddefined node
Good, @@samp@{@@@@node@} is defined.
@@end ifcommanddefined
@end example

@noindent will output the expected `Good, @samp{@@node} is defined.'.

This conditional will also consider any new commands defined by
the document via @code{@@macro}, @code{@@alias},
@code{@@definfoenclose}, and @code{@@def@r{(}code@r{)}index}
(@pxref{Defining New Texinfo Commands}) to be true.  Caveat: the @TeX{}
implementation reports internal @TeX{} commands, in addition to all
the Texinfo commands, as being ``defined''; the @code{texi2any}
implementation is reliable in this regard, however.

@pindex @file{NEWS} file for Texinfo
You can check the @file{NEWS} file in the Texinfo source distribution
and linked from the Texinfo home page
(@url{https://www.gnu.org/software/texinfo}) to see when a particular
command was added.

@vindex txicommandconditionals
These command-checking conditionals themselves were added in
Texinfo@tie{}5.0, released in 2013---decades after Texinfo's
inception.  In order to test if they themselves are available,
the predefined flag @code{txicommandconditionals} can be tested, like
this:

@example
@@ifset txicommandconditionals
@@ifcommandnotdefined foobarnode
(Good, @@samp@{@@@@foobarnode@} is not defined.)
@@end ifcommandnotdefined
@@end ifset
@end example

Since flags (see the previous section) were added early in the
existence of Texinfo, there is no problem with assuming they are
available.

We recommend avoiding these tests whenever possible---which is usually
the case.  For many software packages, it is reasonable for all
developers to have a given version of Texinfo (or newer) installed,
and thus no reason to worry about older versions.  (It is
straightforward for anyone to download and install the Texinfo source;
it does not have any problematic dependencies.)

The issue of Texinfo versions does not generally arise for end users.
With properly distributed packages, users need not process the Texinfo
manual simply to build and install the package; they can use
preformatted Info (or other) output files.  This is desirable in
general, to avoid unnecessary dependencies between packages
(@pxref{Releases,,, standards, GNU Coding Standards}).


@node Conditional Nesting
@nodedescription Using conditionals inside conditionals.
@section Conditional Nesting
@cindex Conditionals, nested
@cindex Nesting conditionals

Texinfo requires that for a failing conditional, the
ignored text must be properly nested with respect to that failing
conditional.  Here's an example:

@example
@@ifset somevar
@@ifset anothervar
Both somevar and anothervar are set.
@@end ifset
@@ifclear anothervar
Somevar is set, anothervar is not.
@@end ifclear
@@end ifset
@end example

If @samp{somevar} is not set, the whole block is skipped.

To allow the processors to reliably determine which commands to consider
for nesting purposes, all conditional commands must be on lines
by themselves, with no text (even spaces) before or after.


@ignore @c not sure what this is about

Unfortunately, it's not always feasible to check that
@emph{all} conditionals are properly nested, because then the
processors could have to fully interpret the ignored text, which
defeats the purpose of the command.  Here's an example illustrating
these rules:

@example
@@ifset a
@@ifset b
@@ifclear ok  - ok, ignored
@@end junky   - ok, ignored
@@end ifset
@@c WRONG - missing @@end ifset.
@end example

@end ignore



@node Defining New Texinfo Commands
@nodedescription User-defined macros and aliases.
@chapter Defining New Texinfo Commands

@cindex Macros
@cindex Defining new Texinfo commands
@cindex New Texinfo commands, defining
@cindex Texinfo commands, defining new
@cindex User-defined Texinfo commands

Texinfo provides several ways to define new commands (in all cases,
it's not recommended to try redefining existing commands):

@itemize @bullet
@item
A Texinfo @dfn{macro} allows you to define a new Texinfo command as any
sequence of text and/or existing commands (including other macros).  The
macro can have any number of @dfn{parameters}---text you supply each
time you use the macro.

Incidentally, these macros have nothing to do with the @code{@@defmac}
command, which is for documenting macros in the subject area of the
manual (@pxref{Def Cmd Template}).

@item
@samp{@@linemacro} allows you to define a macro whose arguments
extend to the end of the line and are separated by spaces.

@item
@samp{@@alias} defines a new name for an existing command.

@item
@samp{@@definfoenclose} allows you to define new commands with
customized output for some non-printed output formats.  This command
is deprecated.

@end itemize

Most generally of all (not just for defining new commands), it is
possible to invoke any external macro processor and have Texinfo
recognize so-called @code{#line} directives for error reporting.

If you want to do simple text substitution, @code{@@set} and
@code{@@value} is the simplest approach (@pxref{@code{@@set @@clear
@@value}}).


@node Defining Macros
@nodedescription Defining and undefining new commands.
@section Defining Macros
@cindex Defining macros
@cindex Macro definitions, Texinfo

@findex macro
You use the Texinfo @code{@@macro} command to define a macro, like this:

@example
@@macro @var{macroname}@{@var{param1}, @var{param2}, @dots{}@}
@var{text} @dots{} \@var{param1}\ @dots{}
@@end macro
@end example

The @dfn{parameters} @var{param1}, @var{param2}, @dots{} correspond to
arguments supplied when the macro is subsequently used in the document
(described in the next section).

@cindex Macro names, valid characters in
@cindex Names of macros, valid characters of
In principle, @var{macroname} should consist of alphanumerics,
and (except as the first character) @samp{-}.  The @samp{_} character
is excluded so that macros can be called inside @code{@@math} without
a following space (@pxref{Inserting Math}).  However, for a macro to
work consistently with @TeX{}, @var{macroname} must consist entirely
of letters: no digits, hyphens, or other special characters.
So, we recommend using only letters.  Texinfo commands should not
be redefined as macros.

If a macro needs no parameters, you can define it either with an empty
list (@samp{@@macro foo @{@}}) or with no braces at all (@samp{@@macro
foo}).

@cindex Body of a macro
The definition or @dfn{body} of the macro can contain most Texinfo
commands, including macro invocations.  However, a macro definition
that defines another macro does not work in @TeX{} due to limitations
in the design of @code{@@macro}.

@cindex Parameters to macros
In the macro body, instances of a parameter name surrounded by
backslashes, as in @samp{\@var{param1}\} in the example above, are
replaced by the corresponding argument from the macro invocation.  You
can use parameter names any number of times in the body, including zero.

@cindex Backslash in macros
To get a single @samp{\} in the macro expansion, use @samp{\\}.  Any
other use of @samp{\} in the body yields a warning.

@cindex Spaces in macros
@cindex Whitespace in macros
The newline characters after the @code{@@macro} line and before the
@code{@@end macro} line are ignored, that is, not included in the
macro body.  All other whitespace is treated according to the usual
Texinfo rules.

@cindex Recursive macro invocations
@findex rmacro
To allow a macro to be used recursively, that is, in an argument to a
call to itself, you must define it with @samp{@@rmacro}, like this:

@example
@@rmacro rmac @{arg@}
a\arg\b
@@end rmacro
@dots{}
@@rmac@{1@@rmac@{text@}2@}
@end example

This produces the output `a1atextb2b'.  With @samp{@@macro} instead of
@samp{@@rmacro}, an error message is given.

@findex unmacro
@cindex Macros, undefining
@cindex Undefining macros
You can undefine a macro @var{foo} with @code{@@unmacro @var{foo}}.
It is not an error to undefine a macro that is already undefined.
For example:

@example
@@unmacro foo
@end example


@node Invoking Macros
@nodedescription Using a macro, once you've defined it.
@section Invoking Macros

@cindex Invoking macros
@cindex Expanding macros
@cindex Running macros
@cindex Macro invocation

After a macro is defined (see the previous section), you can
@dfn{invoke} (use) it in your document like this:

@example
@@@var{macroname} @{@var{arg1}, @var{arg2}, @dots{}@}
@end example

@noindent and the result will be more or less as if you typed the body of
@var{macroname} at that spot.  For example:

@example
@@macro foo @{p, q@}
Together: \p\ & \q\.
@@end macro
@@foo@{a, b@}
@end example

@noindent produces:

@display
Together: a & b.
@end display

@cindex Backslash, and macros
Thus, the arguments and parameters are separated by commas and
delimited by braces; any whitespace after (but not before) a comma is
ignored.  The braces are required in the invocation even when the
macro takes no arguments, consistent with other Texinfo commands.  For
example:

@example
@@macro argless @{@}
No arguments here.
@@end macro
@@argless@{@}
@end example

@noindent produces:

@display
No arguments here.
@end display

@cindex Comma, in macro arguments
Passing macro arguments containing commas requires care, since
commas also separate the arguments.  To include a comma character in
an argument, the most reliable method is to use the @code{@@comma@{@}}
command.  Another method is to surround the argument with
@samp{@@asis@{@dots{}@}}.  For @code{texi2any}, you can also prepend a
backslash character, as in @samp{\,}, but this does not work with @TeX{}.

@cindex Automatic quoting of commas for some macros
@cindex Quoting, automatic for some macros
It's not always necessary to worry about commas.  To facilitate use of
macros, two rules for @dfn{automatic quoting} are implemented:

@enumerate 1
@item If a macro takes only one argument, all commas in its invocation
are quoted by default.  For example:

@example
@group
@@macro TRYME@{text@}
@@strong@{TRYME: \text\@}
@@end macro

@@TRYME@{A nice feature, though it can be dangerous.@}
@end group
@end example

@noindent
will produce the following output

@example
@strong{TRYME: A nice feature, though it can be dangerous.}
@end example

And indeed, it can.  Namely, there is no control on the
number of arguments passed to one-argument macros, so be careful when
you invoke them.

@item If a macro invocation includes another command (including a
recursive invocation of itself), any commas in the nested command
invocation(s) are quoted by default.  For example, in

@example
@@say@{@@strong@{Yes, I do@}, person one@}
@end example

the comma after @samp{Yes} is implicitly quoted.  Here's another
example, with a recursive macro:

@example
@group
@@rmacro cat@{a,b@}
\a\\b\
@@end rmacro

@@cat@{@@cat@{foo, bar@}, baz@}
@end group
@end example

@noindent
will produce the string @samp{foobarbaz}.

@item Otherwise, a comma should be explicitly quoted, as above, for it
to be treated as a part of an argument.
@end enumerate

@cindex Backslash, in macro arguments
@cindex Braces, in macro arguments
The backslash itself can be quoted in macro arguments with another
backslash.  For example:

@example
@@@var{macname} @{\\bleh@}
@end example

@noindent
will pass the argument @samp{\bleh} to @var{macname}.

@command{texi2any} also recognizes @samp{\@{} and @samp{\@}} sequences
for curly braces, but these are not recognized by the implementation in
@TeX{}.  There should, however, rarely be a need for these, as they are
only needed when a macro argument contains unbalanced braces.

If a macro is defined to take exactly one argument, it can be
invoked without any braces, taking all of the line after the macro name
as the argument.  For example:

@example
@@macro bar @{p@}
Twice: \p\ & \p\.
@@end macro
@@bar aah
@end example

@noindent produces:

@display
Twice: aah & aah.
@end display

@noindent
In these arguments, there is no escaping of special characters, so each
@samp{\} stands for itself.

If a macro is defined to take more than one argument, but is called
with only one (in braces), the remaining arguments are set to the
empty string, and no error is given.  For example:

@example
@@macro addtwo @{p, q@}
Both: \p\\q\.
@@end macro
@@addtwo@{a@}
@end example

@noindent produces simply:

@display
Both: a.
@end display


@node Macro Details
@nodedescription Limitations of Texinfo macros.
@section Macro Details and Caveats
@cindex Macro details
@cindex Details of macro usage
@cindex Caveats for macro usage

@cindex Macro expansion, contexts for
@cindex Expansion of macros, contexts for
By design, macro expansion should not happen in the following contexts:

@itemize @bullet
@item @code{@@macro} and @code{@@unmacro} lines;

@item @code{@@if...} lines, including @code{@@ifset} and similar;

@item @code{@@set}, @code{@@clear}, @code{@@value};

@item @code{@@end} lines when there is no macro expansion in the block
command.
@end itemize

@noindent Unfortunately, @TeX{} may do some expansion in these situations,
possibly yielding errors.

Also, quite a few macro-related constructs cause problems with @TeX{};
some of the caveats are listed below.  Thus, if you get macro-related
errors when producing the printed version of a manual, you might try
expanding the macros with @command{texi2any} by invoking
@command{texi2dvi} with the @samp{-E} option (@pxref{Format with
@command{texi2dvi}}).  Or, more reliably, eschew Texinfo macros altogether
and use a language designed for macro processing, such as M4
(@pxref{External Macro Processors}).

@itemize @bullet
@item
As mentioned earlier, macro names must consist entirely of letters.

@item
It is not advisable to redefine any @TeX{} primitive, plain, or
Texinfo command name as a macro. Unfortunately, this is a large and
open-ended set of names, and the possible resulting errors are
unpredictable.

@item
Arguments to macros taking more than one argument cannot cross lines.

@item
Macros containing a command which must be on a line by itself, such as
a conditional, cannot be invoked in the middle of a line.  Similarly,
macros containing line-oriented commands or text, such as
@code{@@example} environments, may behave unpredictably in @TeX{}.

@item
Texinfo commands in the expansion of a macro in the text of an index 
entry may end up being typeset as literal text (including an ``@@'' 
sign), instead of being interpreted with their intended meaning.

@item
White space is ignored at the beginnings of lines.

@item
Macros can't be reliably used in the argument to accent commands
(@pxref{Inserting Accents}).

@item
Macros should not be used in node names.  @xref{Node Names}.

@item
The backslash escape for commas in macro arguments does not work;
@code{@@comma@{@}} must be used.

@item
Ending a macro body with @samp{@@c} may cause text following the macro
invocation to be ignored as a comment in @command{texi2any}.  This is 
not the case when processing with @TeX{}.  This was often done
to ``comment out'' an unwanted newline at the end of a macro body, but 
this is not necessary any more, as the final newline before @samp{@@end 
macro} is not included in the macro body anyway.

@item
In general, you can't arbitrarily substitute a macro (or
@code{@@value}) call for Texinfo command arguments, even when the text
is the same.  Texinfo is not M4 (or even plain @TeX{}).  It might work
with some commands, it fails with others.  Best not to do it at all.
For instance, this fails:

@example
@@macro offmacro
off
@@end macro
@@headings @@offmacro
@end example

@noindent
This looks equivalent to @code{@@headings off}, but for @TeX{}nical
reasons, it fails with a mysterious error message (namely,
@samp{Paragraph ended before @@headings was complete}).

@item
Expanding macros in a math context may lead to poor spacing in
@TeX{} output.  For example:

@example
@@iftex
@@macro atan
\\mathop@{\\rm atan@}
@@end macro
@@end iftex

@@math@{@@atan@{@}(x)@}
@end example

The braces following @samp{@@atan} are treated by @TeX{} as a subformula,
leading to extra space before the opening parenthesis.  You can work
around this by defining a raw @TeX{} macro instead:

@example
@@tex
\gdef\atan#1@{\mathop@{\rm atan@}@}
@@end tex
@end example

The @samp{#1} in this definition absorbs the braces, so that the spacing
is as expected for the @code{\mathop} object.

@item
If you have problems using conditionals within a macro, an alternative
is to use separate macro definitions inside conditional blocks.  For
example, instead of

@example
@group
@@macro Mac
@@iftex
text for TeX output
@@end iftex
@@ifnottex
text for not TeX output
@@end ifnottex
@@end macro
@end group
@end example

@noindent you can do the following instead:

@example
@group
@@iftex
@@macro Mac
text for TeX output
@@end macro
@@end iftex

@@ifnottex
@@macro Mac
text for not TeX output
@@end macro
@@end ifnottex
@end group
@end example



@item
Macros cannot define macros in the natural way.  To do this, you must
use conditionals and raw @TeX{}.  For example:

@example
@@ifnottex
@@macro ctor @{name, arg@}
@@macro \name\
something involving \arg\ somehow
@@end macro
@@end macro
@@end ifnottex
@@tex
\gdef\ctor#1@{\ctorx#1,@}
\gdef\ctorx#1,#2,@{\def#1@{something involving #2 somehow@}@}
@@end tex
@end example
@end itemize

The following limitations are by design:

@itemize
@item
If you want to pass an argument with the Texinfo command 
@code{@@,} (to produce a cedilla, see @ref{Inserting Accents}), you have 
to use @code{@@value} or another workaround.  Otherwise, the comma
may be taken as separating the arguments.  With @command{texi2any},
the comma can be escaped by a backslash.  With @TeX{} another workaround
need to be used, therefore we recommend using such a workaround.

For example,

@example
@@macro mactwo@{argfirst, argsecond@}
\argfirst\+\argsecond\.
@@end macro
@@set fc Fran@@,cois
@@mactwo@{@@value@{fc@},@}
@end example

@noindent produces:

@display
Fran@,cois+.
@end display

@c currently @mactwo{Fran@,cois} works in TeX, but @mactwo{Franc@\,cois}
@c works in texi2any.  better to avoid commas altogether using this trick.
@c an alternative to @, could be invented if needed.

@item
@code{@@verbatim} and macros do not mix; for instance, you can't start
a verbatim block inside a macro and end it outside
(@pxref{@code{@@verbatim}}).  Starting any environment inside a macro
and ending it outside may or may not work, for that matter.

@item
Macros that completely define macros are ok, but it's not possible to
have incompletely nested macro definitions.  That is, @code{@@macro}
and @code{@@end macro} (likewise for @code{@@rmacro}) must be
correctly paired.  For example, you cannot start a macro definition
within a macro, and then end that nested definition outside the macro.
@end itemize

@c Texinfo 5.0 released in 2013
In the @command{makeinfo} implementation before Texinfo 5.0, ends of
lines from expansion of a @code{@@macro} definition did not end an
@@-command line-delimited argument (@code{@@chapter}, @code{@@center},
etc.).  This is no longer the case.  For example:

@example
@@macro twolines@{@}
aaa
bbb
@@end macro
@@center @@twolines@{@}
@end example

In the current @code{texi2any}, this is equivalent to:

@example
@@center aaa
bbb
@end example

@noindent with just @samp{aaa} as the argument to @code{@@center}.  In
the earlier implementation, it would have been parsed as this:

@example
@@center aaa bbb
@end example


@node @code{@@alias}
@nodedescription Command aliases.
@section @samp{@@alias @var{new}=@var{existing}}

@anchor{alias}@c old name
@cindex Aliases, command
@cindex Command aliases
@findex alias

The @samp{@@alias} command defines a new command to be just like an
existing one.  This is useful for defining additional markup names,
thus preserving additional semantic information in the input even
though the output result may be the same.

Write the @samp{@@alias} command on a line by itself, followed by the
new command name, an equals sign, and the existing command name.
Whitespace around the equals sign is optional and ignored if present.
Thus:

@example
@@alias @var{new} = @var{existing}
@end example

For example, if your document contains citations for both books and
some other media (movies, for example), you might like to define a
macro @code{@@moviecite@{@}} that does the same thing as an ordinary
@code{@@cite@{@}} but conveys the extra semantic information as well.
You'd do this as follows:

@example
@@alias moviecite = cite
@end example

Macros do not always have the same effect as aliases, due to vagaries
of argument parsing.  Also, aliases are much simpler to define than
macros.  So the command is not redundant.

Unfortunately, it's not possible to alias Texinfo environments; for
example, @code{@@alias lang=example} is an error.

Aliases must not be recursive, directly or indirectly.

It is not advisable to redefine any @TeX{} primitive, plain @TeX{}, or
Texinfo command name as an alias.  Unfortunately this is a very large
set of names, and the possible resulting errors from @TeX{} are
unpredictable.

Alias identifiers should be the same as for macro names, that is
alphanumerics and (except as the first character) @samp{-}.  However,
with @TeX{}, letters only should be used.  So, we recommend using only
letters.


@node Line Macros
@nodedescription Macros using whole line for arguments.
@section Line Macros

@findex linemacro
@cindex Line macros
@cindex Macros taking whole line as an argument
You can also define a macro using the @samp{@@linemacro} command.
The syntax for line macro definitions is similar to that for
@code{@@macro}.

However, the syntax for using a macro defined this way is different.
The macro call uses the rest of the line, with arguments separated
by spaces.  The line macro facility is mainly intended to allow you
to define commands that operate similarly to the builtin commands
for providing definitions (@pxref{Definition Commands}).

For example:

@example
@@linemacro defbuiltin @{name, args@}
@@defline @{Builtin@} \name\ \args\
@@end linemacro
@end example

The above macro may be used as

@example
@@defblock
@@defbuiltin foo (bar)
Explanation
@@end defblock
@end example

This produces the following result:

@linemacro defbuiltin {name, args}
@defline {Builtin} \name\ \args\
@end linemacro

@defblock
@defbuiltin foo (bar)
Explanation
@end defblock

Here the first argument is @samp{foo}, and is substituted where
@samp{\name\} appears in the macro body.  Likewise, @samp{(bar)}
is substituted for @samp{\args\}.

You can include spaces in a macro argument by surrounding the argument
by braces.  Any pair of braces enclosing an argument is removed
before substitution.  Any empty arguments (including the last one)
must be given as @samp{@{@}}.  Additionally, non-initial spaces may
appear in the final argument in the argument list without surrounding
braces (as in the example below).

If an argument line for a line macro ends in a @samp{@@} character,
then this character together with the following newline are included
in a macro argument, and the following line in the input file is also
used to get the arguments for the macro.  Note that any substitution
of the @samp{@@@var{<newline>}} sequence must be in a valid context,
such as a definition line (@pxref{Def Cmd Continuation Lines}).

Another example:

@example
@@linemacro deffunc @{type, name, args@}
@@findex \name\
@@deftypeline @{Func@} @{\type\@} \name\ \args\
@@end linemacro

@@defblock
@@deffunc @{long int@} F (int @@var@{one@}, int @@var@{two@}, @@
int @@var@{three@}, int @@var@{four@}, int @@var@{five@})
Explanation
@@end defblock
@end example

@noindent Note how braces are needed around @samp{\type\} in the
macro body in case the @code{type} argument contains a space.
This example produces the output below and enters an index entry
for @code{F}.

@linemacro deffunc {type, name, args}
@c @findex \name\
@deftypeline {Func} {\type\} \name\ \args\
@end linemacro

@defblock
@deffunc {long int} F (int @var{one}, int @var{two}, @
int @var{three}, int @var{four}, int @var{five})
Explanation
@end defblock

Line macros produce a whole number of lines of output in their expansion.
There may be better compatibility between the Texinfo processors
(@command{texi2any} and @TeX{} with @file{texinfo.tex}) for macros defined
with @code{@@linemacro} than for those defined with @code{@@macro}.


@node @code{@@definfoenclose}
@nodedescription Customized highlighting.
@section @code{@@definfoenclose}: Customized Highlighting

@anchor{definfoenclose}@c old name
@cindex Highlighting, customized
@findex definfoenclose

An @code{@@definfoenclose} command may be used to define a
highlighting command for online output formats.  A command
defined using @code{@@definfoenclose} marks text by enclosing it in
strings that precede and follow the text.

In practice, there is little use for this command, and we do not
recommend you use it.  Support for @code{@@definfoenclose} may be
removed in future releases of Texinfo.

Write a @code{@@definfoenclose} command at the beginning of a line
followed by three comma-separated arguments.  The first argument to
@code{@@definfoenclose} is the @@-command name (without the
@code{@@}); the second argument is the start delimiter string; and the
third argument is the end delimiter string.  The latter two arguments
enclose the highlighted text in the output.

A delimiter string may contain spaces.  Neither the start nor end
delimiter is required.  If you do not want a start delimiter but do
want an end delimiter, you must follow the command name with two
commas in a row; otherwise, the end delimiter string you intended will
naturally be (mis)interpreted as the start delimiter string.

An enclosure command defined this way takes one argument in braces,
since it is intended for new markup commands (@pxref{Marking Text}).

@findex phoo
For example, you can write:

@example
@@definfoenclose phoo,//,\\
@end example

@noindent
near the beginning of a Texinfo file to define @code{@@phoo} as an Info
and HTML command that inserts `//' before and `\\' after the
argument to @code{@@phoo}.  You can then write @code{@@phoo@{bar@}}
wherever you want `//bar\\' highlighted in Info and HTML.

For @TeX{} formatting, you could write

@example
@@iftex
@@alias phoo = i
@@end iftex
@end example

@noindent
to define @code{@@phoo} as a command that causes @TeX{} to typeset the
argument to @code{@@phoo} in italics.

Each definition applies to its own formatter: one for @TeX{}, the
other for online formats.  The @TeX{} definitions need to be in
@samp{@@iftex}.  @code{@@definfoenclose} command need not be within
@samp{@@ifinfo} unless you want to use different definitions for
different online output formats.  @code{@@definfoenclose} defined
commands have no effect in DocBook and @LaTeX{} output, their
argument is output as-is.  An @code{@@alias} could also be used
for these formats.

@code{@@definfoenclose} definitions must not be recursive, directly or
indirectly.


@node External Macro Processors
@nodedescription @code{#line} directives.
@section External Macro Processors: Line Directives
@cindex External macro processors
@cindex Macro processors, external

Texinfo macros (and its other text substitution facilities) work fine
in straightforward cases.  If your document needs unusually complex
processing, however, their fragility and limitations can be a problem.
In this case, you may want to use a different macro processor
altogether, such as M4 (@pxref{Top,,, m4, M4}) or CPP (@pxref{Top,,,
cpp, The C Preprocessor}).

With one exception, Texinfo does not need to know whether its input is
``original'' source or preprocessed from some other source file.
Therefore, you can arrange your build system to invoke whatever
programs you like to handle macro expansion or other preprocessing
needs.  Texinfo does not offer built-in support for any particular
preprocessor, since no one program seemed likely to suffice for the
requirements of all documents.

@cindex Line numbers, in error messages
@cindex Error messages, line numbers in
The one exception is line numbers in error messages.  In that case,
the line number should refer to the original source file, whatever it
may be.  There's a well-known mechanism for this: the so-called
@samp{#line} directive.  Texinfo supports this.


@node @samp{#line} Directive
@subsection @samp{#line} Directive

@cindex @samp{#line} directive

An input line such as this:

@example
@hashchar{}line 100 "foo.ptexi"
@end example

@noindent indicates that the next line was line 100 of the file
@file{foo.ptexi}, and so that's what an error message should refer to.
Both M4 (@pxref{Preprocessor features,,, m4, GNU M4}) and CPP
(@pxref{Line Control,,, cpp, The C Preprocessor}, and
@ref{Preprocessor Output,,, cpp, The C Preprocessor}) can generate
such lines.

The @command{texi2any} program recognizes these lines by default,
except within @code{@@verbatim} blocks (@pxref{@code{@@verbatim}}).
Their recognition can be turned off completely with
@code{CPP_LINE_DIRECTIVES} (@pxref{Global Customization Variables}),
though there is normally no reason to do so.

For those few programs (M4, CPP, Texinfo) which need to document
@samp{#line} directives and therefore have examples which would
otherwise match the pattern, the command @code{@@hashchar@{@}} can be
used (@pxref{Inserting a Hashsign}).  The example line above looks
like this in the source for this manual:

@example
@@hashchar@{@}line 100 "foo.ptexi"
@end example

The @code{@@hashchar} command was added to Texinfo in 2013.  If you
don't want to rely on it, you can also use @code{@@set} and
@code{@@value} to insert the literal @samp{#}:

@example
@@set hash #
@@value@{hash@}line 1 "example.c"
@end example

Or, if suitable, a @code{@@verbatim} environment can be used instead
of @code{@@example}.  As mentioned above, @code{#line}-recognition is
disabled inside verbatim blocks.


@node @samp{#line} and @TeX{}
@subsection @samp{#line} and @TeX{}

@cindex @TeX{} and @samp{#line} directives
@cindex @samp{#line} directive @subentry not processing with @TeX{}

As mentioned, @command{texi2any} recognizes the @samp{#line}
directives described in the previous section.  However,
@file{texinfo.tex} does not and cannot.  Therefore, such a line will
be incorrectly typeset verbatim if @TeX{} sees it.  The solution is to
use @command{texi2any}'s macro expansion options before running
@TeX{}.  There are three approaches:

@itemize @bullet
@item
If you run @command{texi2dvi} or its variants (@pxref{Format with
@command{texi2dvi}}), you can pass @option{-E} and @command{texi2dvi}
will run @command{texi2any} first to expand macros and eliminate
@samp{#line}.

@item
If you run @command{texi2any}, you can specify @option{--no-ifinfo
--iftex -E somefile.out}, and then give @file{somefile.out} to
@command{texi2dvi} in a separate command.

@item
Or you can run @option{texi2any --dvi --Xopt -E}.  (Or @option{--pdf}
instead of @option{--dvi}.)  @command{texi2any} will then call
@command{texi2dvi -E}.
@end itemize

@findex errormsg@r{, and line numbers in @TeX{}}
One last caveat regarding use with @TeX{}: since the @code{#line}
directives are not recognized, the line numbers emitted by the
@code{@@errormsg@{@}} command (@pxref{Conditional Commands}), or by
@TeX{} itself, are the (incorrect) line numbers from the derived file
which @TeX{} is reading, rather than the preprocessor-specified line
numbers.


@node @samp{#line} Syntax Details
@subsection @samp{#line} Syntax Details

@cindex @samp{#line} directive @subentry syntax details
@cindex Syntax details, @samp{#line}
@cindex Regular expression, for @samp{#line}

Syntax details for the @samp{#line} directive: the @samp{#} character
can be preceded or followed by whitespace, the word @samp{line} is
optional, and the file name can be followed by a whitespace-separated
list of integers (these are so-called ``flags'' output by CPP in some
cases).  For those who like to know the gory details, the actual
(Perl) regular expression which is matched is this:

@example
/^\s*#\s*(line)? (\d+)(( "([^"]+)")(\s+\d+)*)?\s*$/
@end example

As far as we've been able to tell, the trailing integer flags only
occur in conjunction with a file name, so that is reflected in the
regular expression.

As an example, the following is a syntactically valid @samp{#line}
directive, meaning line 1 of @file{/usr/include/stdio.h}:

@example
@hashchar{} 1 "/usr/include/stdio.h" 2 3 4
@end example

Unfortunately, the quoted file name (@samp{"..."}) has to be optional,
because M4 (especially) can often generate @samp{#line} directives
within a single file.  Since the @samp{line} is also optional, the
result is that lines might match which you wouldn't expect, e.g.,

@example
@hashchar{} 1
@end example

The possible solutions are described above (@pxref{@samp{#line} Directive}).


@node Include Files
@nodedescription How to incorporate other Texinfo files.
@chapter Include Files

@cindex Include files

When a Texinfo processor sees an @code{@@include} command in a Texinfo
file, it processes the contents of the file named by the
@code{@@include} and incorporates them into the output files being
created.  Include files thus let you keep a single large document as a
collection of conveniently small parts.


@node Using Include Files
@nodedescription How to use the @code{@@include} command.
@section How to Use Include Files

@findex include

To include another file within a Texinfo file, write the
@code{@@include} command at the beginning of a line and follow it on
the same line by the name of a file to be included.  For example:

@example
@@include buffers.texi
@end example

@code{@@value@{@var{var}@}} references are expanded on the @code{@@include}
line.  Other than that, the only @@-commands allowed are @code{@@@@},
@code{@@@{}, @code{@@@}} and associated @@-commands such as
@code{@@atchar@{@}}.

An included file should simply be a segment of text that you expect to
be included as is into the overall or @dfn{outer} Texinfo file; it
should not contain the standard beginning and end parts of a Texinfo
file.  In particular, you should not start an included file with a
line saying @samp{\input texinfo}; if you do, that text is inserted
into the output file literally.  Likewise, you should not end an
included file with a @code{@@bye} command; nothing after @code{@@bye}
is formatted.

In the long-ago past, you were required to write an
@code{@@setfilename} line at the beginning of an included file, but no
longer.  Now, it does not matter whether you write such a line.  If an
@code{@@setfilename} line exists in an included file, it is ignored.

GNU Emacs Texinfo mode provides @code{texinfo-multiple-files-update}
to update node pointers and master menu with multiple include files.
@xref{Update Multiple Files}.


@node Sample Include File
@nodedescription A sample outer file with included files within it; and a sample included file.
@section Sample File with @code{@@include}
@cindex Sample @code{@@include} file
@cindex Include file sample
@cindex @code{@@include} file sample

Here is an example of an outer Texinfo file with @code{@@include} files
within it:

@example
@group
\input texinfo @@c -*-texinfo-*-

@@settitle Include Example

@end group

@group
@@node Top
@@top Include Example
@end group

@group
@@include foo.texi
@@include bar.texi
@@include concept-index.texi
@@bye
@end group
@end example

An included file, such as @file{foo.texi}, might look like this:

@example
@group
@@node First
@@chapter First Chapter

Contents of first chapter @dots{}
@end group
@end example

The full contents of @file{concept-index.texi} might be as simple as this:

@example
@group
@@node Concept Index
@@unnumbered Concept Index

@@printindex cp
@end group
@end example

@c FIXME not sure that this is of general interest for Texinfo
The outer Texinfo source file for @cite{The GNU Emacs Lisp Reference
Manual} is named @file{elisp.texi}.  This outer file
has already contained a master menu with 417 entries and a list of
41 @code{@@include} files.


@node @code{@@verbatiminclude}
@nodedescription Including a file verbatim.
@section @code{@@verbatiminclude} @var{file}: Include a File Verbatim

@anchor{verbatiminclude}@c old name
@findex verbatiminclude
@cindex Verbatim, include file
@cindex Including a file verbatim

You can include the exact contents of a file in the document with the
@code{@@verbatiminclude} command:

@example
@@verbatiminclude @var{filename}
@end example

The contents of @var{filename} is printed in a verbatim environment
(@pxref{@code{@@verbatim}}).  Generally, the file is printed exactly
as it is, with all special characters and white space retained.  No
indentation is added; if you want indentation, enclose the
@code{@@verbatiminclude} within @code{@@example}
(@pxref{@code{@@example}}).

@code{@@value@{@var{var}@}} references are expanded on the
@code{@@verbatiminclude} line.  This makes it possible to
include files in other directories within a distribution,
for instance:

@example
@@verbatiminclude @@value@{top_srcdir@}/NEWS
@end example

@noindent (You still have to get @code{top_srcdir} defined in the
first place.)

Other than that, the only @@-commands allowed are @code{@@@@},
@code{@@@{}, @code{@@@}} and associated @@-commands such as
@code{@@atchar@{@}}.

For a method on printing the file contents in a smaller font size, see
the end of the section on @code{@@verbatim}.


@ignore

@node Include Files Evolution
@section Evolution of Include Files

When Info was first created, it was customary to create many small
Info files on one subject.  Each Info file was formatted from its own
Texinfo source file.  This custom meant that Emacs did not need to
make a large buffer to hold the whole of a large Info file when
someone wanted information; instead, Emacs allocated just enough
memory for the small Info file that contained the particular
information sought.  This way, Emacs could avoid wasting memory.

References from one file to another were made by referring to the file
name as well as the node name. (@xref{Other Info Files, , Referring to
Other Info Files}.  Also, see @ref{Four and Five Arguments, ,
@code{@@xref} with Four and Five Arguments}.)

Include files were designed primarily as a way to create a single,
large printed manual out of several smaller Info files.  In a printed
manual, all the references were within the same document, so @TeX{}
could automatically determine the references' page numbers.  The Info
formatting commands used include files only for creating joint
indices; each of the individual Texinfo files had to be formatted for
Info individually.  (Each, therefore, required its own
@code{@@setfilename} line.)

However, because large Info files are now split automatically, it is
no longer necessary to keep them small.

Nowadays, multiple Texinfo files are used mostly for large documents,
such as @cite{The GNU Emacs Lisp Reference Manual}, and for projects
in which several different people write different sections of a
document simultaneously.

In addition, the Info formatting commands have been extended to work
with the @code{@@include} command so as to create a single large Info
file that is split into smaller files if necessary.  This means that
you can write menus and cross-references without naming the different
Texinfo files.

@end ignore


@node Hardcopy with @TeX{}
@nodedescription Output for paper, with @TeX{}.
@chapter Formatting and Printing with @TeX{}
@anchor{Hardcopy} @c old name
@anchor{Printing}
@cindex Format and print hardcopy
@cindex Printing hardcopy
@cindex Hardcopy, printing it
@cindex Making a printed manual
@cindex Sorting indices
@cindex Indices, sorting
@cindex @TeX{} index sorting

Running the @command{texi2dvi} or @command{texi2pdf} command is the
simplest way to create printable output.  These commands are installed
as part of the Texinfo package.

In more detail, typesetting and printing a Texinfo file is a multi-step
process in which you use the @TeX{} program to create a file for printing
(called a DVI or PDF file), and then print the file.  Optionally,
you may also create indices using the @command{texindex} command
after first running @TeX{}; and then you must run @TeX{} again.
@command{texi2dvi} takes care of all of this, running @TeX{} and
@command{texindex} as needed (@pxref{Format with @command{texi2dvi}}).

@anchor{Within Emacs} @c old node name
@anchor{Emacs Shell Printing} @c old node name
@cindex Print, format from Emacs shell
@cindex Format, print from Emacs shell
@cindex Shell, format, print from
@cindex Emacs shell, format, print from
@cindex GNU Emacs shell, format, print from
When you use the shell commands, you
can either work directly in the operating system shell or work within
a shell inside GNU Emacs (or some other computing environment).
You can give formatting and printing commands from a shell within GNU
Emacs, just like any other shell command.  To create a shell within
Emacs, type @kbd{M-x shell} (@pxref{Shell,,, emacs, The GNU Emacs Manual}).
If you are using GNU Emacs, you can also use commands provided by Texinfo
mode instead of shell commands.  @xref{Printing with Emacs}.

For specifing details of the printed output such as paper size, see
@ref{Global Document Commands}.


@node Use @TeX{}
@nodedescription Use @TeX{} to format for hardcopy.
@section Use @TeX{}

The typesetting program called @TeX{} is used to format a Texinfo
document for printable output.  @TeX{} is a very powerful typesetting
program and, when used correctly, does an exceptionally good job.  It is 
not included in the Texinfo package, being a vast suite of software
in itself.

@anchor{Obtaining @TeX{}}
@cindex Obtaining @TeX{}
@cindex @TeX{}, how to obtain
@TeX{} is a document formatter that is used by the FSF for its
documentation.  It is the easiest way to get printed output (e.g., PDF
and PostScript) for Texinfo manuals.  TeX is freely redistributable,
and you can get it over the Internet or on physical media.  See
@url{http://tug.org/texlive}.

@c please keep that text in sync with www.gnu.org/prep/FTP


@node Format with @command{texi2dvi} or @command{texi2pdf}
@nodedescription The simplest way to format.
@section Format with @command{texi2dvi} or @command{texi2pdf}

@c previously in a separate node.  To be used when referring
@c only to PDF output, as is the case in @direntry
@anchor{PDF Output}
@c To be used when referring to DVI output or to texi2dvi only,
@c as is the case in @direntry
@anchor{Format with @command{texi2dvi}}

@pindex texi2dvi @r{(shell script)}
@pindex texi2pdf @r{(shell script)}
@cindex DVI, output in
@cindex PDF output
@cindex Output, in PDF

The @command{texi2dvi} program takes care of all the steps for producing
a @TeX{} DVI file from a Texinfo document.  Similarly, @command{texi2pdf}
produces a PDF file@footnote{@dfn{PDF} stands for `Portable Document Format'.
It was invented by Adobe Systems for document interchange, based on their PostScript language.}.

To run @command{texi2dvi} or @command{texi2pdf} on an input file
@file{foo.texi}, do this (where @samp{prompt$ } is your shell prompt):

@example
prompt$ @kbd{texi2dvi foo.texi}
prompt$ @kbd{texi2pdf foo.texi}
@end example

As shown in this example, the file names given to @command{texi2dvi} and
@command{texi2pdf} must include any extension, such as @samp{.texi}.

For a list of all the options, run @samp{texi2dvi --help}.  Some of the
options are discussed below.

@opindex --pdf@r{, for @command{texi2dvi}}
@pindex pdftexi2dvi
With the @option{--pdf} option, @command{texi2dvi} produces PDF output
instead of DVI, by running @command{pdftex}
instead of @command{tex}.  Alternatively, the command
@command{texi2pdf} is an abbreviation for running @samp{texi2dvi
--pdf}.  The command @command{pdftexi2dvi} is also provided as a
convenience for AUC-@TeX{} (@pxref{Top,,, auctex, AUC-@TeX{}}), as it
prefers to merely prepend @samp{pdf} to DVI producing tools to have
PDF producing tools.

@opindex --dvipdf@r{, for @command{texi2dvi}}
@pindex dvipdfmx
With the @option{--dvipdf} option, @command{texi2dvi} produces PDF
output by running @TeX{} and then a DVI-to-PDF program: if the
@env{DVIPDF} environment variable is set, that value is used, else the
first program extant among @code{dvipdfmx}, @code{dvipdfm},
@code{dvipdf}, @code{dvi2pdf}, @code{dvitopdf}.  This method generally
supports CJK typesetting better than @command{pdftex}.

@opindex --ps@r{, for @command{texi2dvi}}
@pindex dvips
With the @option{--ps} option, @command{texi2dvi} produces PostScript
instead of DVI, by running @command{tex} and then @command{dvips}
(@pxref{Top,,, dvips, Dvips}).  (Or the value of the @env{DVIPS}
environment variable, if set.)

@opindex --language@r{, for @command{texi2dvi}}
@cindex @LaTeX{}, processing with @command{texi2dvi}
@command{texi2dvi} can also be used to process @LaTeX{} files.
Normally @command{texi2dvi} is able to guess the input file language
by its contents and file name extension; however, if it guesses wrong
you can explicitly specify the input language using
@option{--language=@var{lang}} command line option, where @var{lang}
is either @samp{latex} or @samp{texinfo}.

@opindex --command@r{, for @command{texi2dvi}}
One useful option to @command{texi2dvi} is @samp{--command=@var{cmd}}.
This inserts @var{cmd} on a line by itself at the start of the file
in a temporary copy of the input file, before
running @TeX{}.  With this, you can specify different printing
formats, such as @code{@@smallbook} (@pxref{@code{@@smallbook}}),
@code{@@afourpaper} (@pxref{A4 Paper}), or @code{@@pagesizes}
(@pxref{@code{@@pagesizes}}), without actually changing the document
source.  (You can also do this on a site-wide basis with
@file{texinfo.cnf}; @pxref{Preparing for @TeX{}}).

The option @option{-E} (equivalently, @option{-e} and
@option{--expand}) does Texinfo macro expansion using
@command{texi2any} instead of the @TeX{} implementation (@pxref{Macro
Details}).  Each implementation has its own limitations and
advantages.

@command{texi2dvi} takes the @option{--build=@var{mode}} option to 
specify where the @TeX{} compilation takes place, and, as a
consequence, how auxiliary files are treated.  The build mode
can also be set using the environment variable 
@env{TEXI2DVI_BUILD_MODE}.  The valid values for @var{mode} are:

@table @samp
@item local
 Compile in the current directory, leaving all the auxiliary
 files around.  This is the traditional TeX use.

@item tidy
 Compile in a local @code{*.t2d} directory, where the auxiliary files
 are left.  Output files are copied back to the original file.

 Using the @samp{tidy} mode brings several advantages:
 @itemize -
 @item the current directory is not cluttered with plethora of temporary files.
 @item clutter can be even further reduced using @option{--build-dir=dir}: all
   the @code{*.t2d} directories are stored there.
 @item clutter can be reduced to zero using, e.g.,
   @option{--build-dir=/tmp/\$USER.t2d} or @option{--build-dir=\$HOME/.t2d}.
 @item the output file is updated after every successful @TeX{} run, for
   sake of concurrent visualization of the output.  In a @samp{local} build
   the viewer stops during the whole @TeX{} run.
 @item if the compilation fails, the previous state of the output file
   is preserved.
 @item @acronym{PDF} and @acronym{DVI} compilation are kept in separate
   subdirectories
   preventing any possibility of auxiliary file incompatibility.
 @end itemize

 On the other hand, because @samp{tidy} compilation takes place in another
 directory, occasionally @TeX{} won't be able to find some files (e.g., when
 using @code{\graphicspath}): in that case, use @option{-I} to specify the
 additional directories to consider.

@item clean
 Same as @samp{tidy}, but remove the auxiliary directory afterwards.
 Every compilation therefore requires the full cycle.
@end table

@pindex etex
@command{texi2dvi} will use @command{etex} if
it is available, because it runs faster in some cases, and
provides additional tracing information when debugging
@file{texinfo.tex}.  Nevertheless, this extended version of @TeX{} is
not required, and the DVI output is identical.

@cindex file recorder for @TeX{}
@cindex @samp{\openout} line in log file
@command{texi2dvi} attempts to detect auxiliary files output by @TeX{}, 
either by using the @option{-recorder} option, or by scanning for 
@samp{\openout} in the log file that a run of @TeX{} produces.  You may
control how @command{texi2dvi} does this with the @env{TEXI2DVI_USE_RECORDER}
environment variable.  Valid values are:

@table @samp
@item yes
use the @option{-recorder} option, no checks.

@item no
scan for @samp{\openout} in the log file, no checks.

@item yesmaybe
check whether @option{-recorder} option is supported, and if yes
use it, otherwise check for tracing @samp{\openout} in the log file is 
supported, and if yes use it, else it is an error.

@item nomaybe
same as @samp{yesmaybe}, except that the @samp{\openout} trace in log 
file is checked first.
@end table

The default is @samp{nomaybe}.  This environment variable is provided 
for troubleshooting purposes, and may change or disappear in the future.


@node Format with @command{tex}/@command{texindex}
@nodedescription Formatting with explicit shell commands.
@section Format with @command{tex}/@command{texindex}

@cindex Shell formatting with @command{tex} and @command{texindex}
@cindex Formatting with @command{tex} and @command{texindex}
@cindex DVI file

You can do the basic formatting of a Texinfo file with the shell
command @command{tex} followed by the name of the Texinfo file.  For
example:

@example
tex foo.texi
@end example

@noindent @TeX{} will produce a @dfn{DVI file} as well as several auxiliary
files containing information for indices, cross-references, etc.  The
DVI file (for @dfn{DeVice Independent} file) can be printed on
virtually any device, perhaps after a further conversion (see the
previous section).

@pindex texindex
The @command{tex} formatting command itself does not sort the indices; it
writes an output file of unsorted index data.  To generate a printed
index after running the @command{tex} command, you first need a sorted
index to work from.  The @command{texindex} command sorts indices.
(@command{texi2dvi}, described in the previous section, runs
@command{tex} and @command{texindex} as necessary.)

@anchor{Names of index files}
@cindex Names of index files
@cindex Index file names
@command{tex} outputs unsorted index files under names following a
standard convention: the name of your main input file with any
@samp{.texi} or similar extension replaced by the two letter index
name.  For example, the raw index output files for the input file
@file{foo.texi} would be, by default, @file{foo.cp}, @file{foo.vr},
@file{foo.fn}, @file{foo.tp}, @file{foo.pg} and @file{foo.ky}.  Those
are exactly the arguments to give to @command{texindex}.

@need 1000
@cindex Wildcards
@cindex Globbing
Instead of specifying all the unsorted index file names explicitly,
it's typical to use @samp{??} as shell wildcards and give the command
in this form:

@example
texindex foo.??
@end example

@noindent
This command will run @command{texindex} on all the unsorted index files,
including any two letter indices that you have defined yourself using
@code{@@defindex} or @code{@@defcodeindex}.  You can safely run
@samp{texindex foo.??} even if there are files with two letter
extensions that are not index files, such as @samp{foo.el}.  The
@command{texindex} command reports but otherwise ignores such files.

For each file specified, @command{texindex} generates a sorted index file
whose name is made by appending @samp{s} to the input file name; for
example, @file{foo.cps} is made from @file{foo.cp}.  The
@code{@@printindex} command looks for a file with that name
(@pxref{Printing Indices & Menus}).  @TeX{} does not read the raw
index output file, and @command{texindex} does not alter it.

After you have sorted the indices, you need to rerun @command{tex} on the
Texinfo file.  This regenerates the output file, this time with
up-to-date index entries.

Finally, you may need to run @command{tex} one more time, to get the page
numbers in the cross-references correct.

To summarize, this is a five-step process.  (Alternatively, it's a
one-step process: run @command{texi2dvi}; see the previous section.)

@enumerate
@item
Run @command{tex} on your Texinfo file.  This generates a DVI file (with
undefined cross-references and no indices), and the raw index files
(with two letter extensions).

@item
Run @command{texindex} on the raw index files.  This creates the
corresponding sorted index files (with three letter extensions).

@item
Run @command{tex} again on your Texinfo file.  This regenerates the DVI
file, this time with indices and defined cross-references, but with
page numbers for the cross-references from the previous run, generally
incorrect.

@item
Sort the indices again, with @command{texindex}.

@item
Run @command{tex} one last time.  This time the correct page numbers are
written for the cross-references.
@end enumerate

@pindex pdftex
To generate PDF, you can run the @command{pdftex}
program instead of plain @command{tex}.  That is, run @command{pdftex
foo.texi} instead of @samp{tex foo.texi} in the examples above.


@node Formatting Partial Documents
@subsection Formatting Partial Documents

@cindex Formatting partial documents
@cindex Partial documents, formatting
@cindex Chapters, formatting one at a time
@cindex Auxiliary files, omitting
@cindex Pointer validation @subentry suppressing
@findex novalidate

Sometimes you may wish to print a document while you know it is
incomplete, or to print just one chapter of a document.  In such a
case, the usual auxiliary files that @TeX{} creates and warnings
@TeX{} gives about undefined cross-references are just nuisances.  You
can avoid them with the @code{@@novalidate} command, which you must
give @emph{before} any sectioning or cross-reference commands.

Thus, the beginning of your file would look approximately like this:

@example
\input texinfo
@@novalidate
@dots{}
@end example

@noindent @code{@@novalidate} also turns off validation in
@command{texi2any}, just like its @code{--no-validate} option
(@pxref{Invoking @command{texi2any}}).

Furthermore, you need not run @command{texindex} each time after you run
@command{tex}.  The @command{tex} formatting command simply uses whatever
sorted index files happen to exist from a previous use of
@command{texindex}.  If those are out of date, that is usually ok while
you are creating or debugging a document.


@node Details of @command{texindex}
@subsection Details of @command{texindex}

@cindex Braces, in index entries
In Texinfo version 6, released in 2015, the @command{texindex} program
was completely reimplemented.  The principal functional difference is
that index entries beginning with a left brace or right brace
(@samp{@{} resp.@: @samp{@}}) can work properly.  For example, these
simple index entries are processed correctly, including the ``index
initial'' shown in the index:

@example
@@cindex @@@{
@@cindex @@@}
...
@@printindex cp
@end example


@node Preparing for @TeX{}
@nodedescription What to do before you use @TeX{}.
@section Preparing for @TeX{}
@cindex Preparing for @TeX{}
@cindex @TeX{} input initialization
@cindex @sortas{profile init} @file{.profile} initialization file
@cindex @sortas{cshrc init} @file{.cshrc} initialization file
@cindex Initialization file for @TeX{} input

@TeX{} needs to find the @file{texinfo.tex} file that the
@samp{\input texinfo} command on the first line reads.  The
@file{texinfo.tex} file tells @TeX{} how to handle @@-commands; it is
included in all standard GNU distributions.  The latest version
released for general use is available
from the usual GNU servers and mirrors:

@display
@uref{https://ftp.gnu.org/gnu/texinfo/texinfo.tex}
@uref{https://ftpmirror.gnu.org/texinfo/texinfo.tex}
@end display

The latest development version is available from the Texinfo source
repository:

@display
@uref{https://git.savannah.gnu.org/cgit/texinfo.git/plain/doc/texinfo.tex}
@end display

@pindex texinfo.tex@r{, installing}
@file{texinfo.tex} is essentially a standalone file,
so, if you need or want to try a newer version
than came with your system, it nearly always suffices to download it
and put it anywhere that @TeX{} will find it.  You can replace
any existing @file{texinfo.tex} with a newer version (of course saving
the original in case of disaster).

@pindex epsf.tex@r{, installing}
Also, you should install @file{epsf.tex}, if it is not already installed
from another distribution.  More details are at the end of the description
of the @code{@@image} command (@pxref{Images}).

@cindex European Computer Modern fonts @subentry installing
@cindex EC fonts, installing
@cindex CM-Super fonts @subentry installing
To use quotation marks other than those used in English, you'll need
to have the European Computer Modern fonts (e.g., @file{ecrm1000}) and
(for PDF output) CM-Super fonts (@pxref{Inserting Quotation Marks}).

@cindex @code{feymr10} @subentry installing
@cindex Euro font, installing
To use the @code{@@euro} command, you'll need the @samp{feym*} fonts
(e.g., @file{feymr10}).  @xref{@code{@@euro}}.

All of the above files should be installed by default in a reasonable 
@TeX{} installation.

@pindex texinfo.cnf @r{installation}
@cindex Customizing of @TeX{} for Texinfo
@cindex Site-wide Texinfo configuration file
Optionally, you may create a file @file{texinfo.cnf} for site configuration.
When processing a Texinfo file, @TeX{} looks for this file
in its search path, which includes the current directory and standard 
installation directories.
You can use this file for local conventions.  For example, if 
@file{texinfo.cnf} contains the line
@samp{@@afourpaper} (@pxref{A4 Paper}), then all Texinfo documents
will be processed with that page size in effect.  If you have nothing
to put in @file{texinfo.cnf}, you do not need to create it.

@cindex Environment variable @code{TEXINPUTS}
@vindex TEXINPUTS
You can set the @code{TEXINPUTS} environment variable
to allow @TeX{} to find @file{texinfo.cnf}.
(This also works for @file{texinfo.tex} and any other file @TeX{}
might read).  For example, if you are using a Bourne shell-compatible shell 
(@code{sh}, @code{bash}, @code{ksh}, @dots{}), your @file{.profile} file
could contain the lines:

@example
TEXINPUTS=.:/home/me/mylib:
export TEXINPUTS
@end example

@noindent
These settings would cause @TeX{} first to look for an @file{\input} file
in the current directory, indicated by the @samp{.}, then in a
hypothetical user @samp{me}'s @file{mylib} directory, and finally in
the system directories.  (A leading, trailing, or doubled @samp{:}
indicates searching the system directories at that point.)


@node Overfull hboxes
@nodedescription What are and what to do with overfull hboxes.
@section Overfull ``hboxes''
@cindex Overfull @samp{hboxes}
@cindex @samp{hbox}, overfull
@cindex Final output

@TeX{} is sometimes unable to typeset a line within the normal
margins.  This most often occurs when @TeX{} comes upon what it
interprets as a long word that it cannot hyphenate, such as an
electronic mail network address or a very long identifier.  When this
happens, @TeX{} prints an error message like this:

@example
Overfull @@hbox (20.76302pt too wide)
@end example

@findex hbox
@noindent
(In @TeX{}, lines are in ``horizontal boxes'', hence the term, ``hbox''.
@samp{@@hbox} is a @TeX{} primitive not used in the Texinfo language.)

@TeX{} also provides the line number in the Texinfo source file and
the text of the offending line, which is marked at all the places that
@TeX{} considered hyphenation.  @xref{Debugging with @TeX{}}, for more
information about typesetting errors.

If the Texinfo file has an overfull hbox, you can rewrite the sentence
so the overfull hbox does not occur, or you can decide to leave it.  A
small excursion into the right margin often does not matter and may not
even be noticeable.

If you have many overfull boxes and/or an antipathy to rewriting, you
can coerce @TeX{} into greatly increasing the allowable interword
spacing, thus (if you're lucky) avoiding many of the bad line breaks,
like this:

@findex \emergencystretch
@example
@@tex
\global\emergencystretch = .9\hsize
@@end tex
@end example

@noindent
(You should adjust the fraction as needed.)  This huge value for
@code{\emergencystretch} cannot be the default, since then the typeset
output would generally be of noticeably lower quality; its default
value is @samp{.15\hsize}.  @code{\hsize} is the @TeX{} dimension
containing the current line width.

@cindex Black rectangle in hardcopy
@cindex Rectangle, black in hardcopy
@cindex Box, ugly black in hardcopy
@cindex Ugly black rectangles in hardcopy
For any overfull boxes you do have, @TeX{} will print a large, ugly,
black rectangle beside the line that contains the overfull hbox unless
told otherwise.  This is so you will notice the location of the
problem if you are correcting a draft.

@findex finalout
To prevent such a monstrosity from marring your final printout, write
the following in the beginning of the Texinfo file on a line of its own,
before the @code{@@maketitle} or @code{@@titlepage} command:

@example
@@finalout
@end example

@node Printing Japanese and Chinese
@nodedescription XeTeX or LuaTeX required.
@section Printing Japanese and Chinese

@cindex Chinese language
@cindex Japanese language
Texinfo comes with support files for processing input in the
Japanese and Chinese languages.

@cindex Japanese with Xe@TeX{}
@cindex Japanese with LuaTeX
For Japanese, you use the @file{texinfo-ja.tex} file. Your main input
file should begin with a @samp{\input texinfo-ja} line, rather than
the standard
@w{@samp{\input texinfo}}.  Use the UTF-8 character encoding as usual.
You must process the files with either Xe@TeX{} or LuaTeX.

@cindex Chinese with Xe@TeX{}
For Chinese, you use the @file{texinfo-zh.tex} file. Your main input
file should begin with a @samp{\input texinfo-zh} line, rather than
the standard
@w{@samp{\input texinfo}}.  Use the UTF-8 character encoding as usual.
You must process the files with Xe@TeX{}.

For example, you would run
@samp{PDFTEX=xetex texi2pdf @var{my-input-file.texi}}
to use Xe@TeX{} to produce PDF output.  You may have to install Xe@TeX{}
(or LuaTeX), the @samp{zhspacing} package, and/or font packages.

Neither Japanese nor Chinese is supported with the standard @TeX{} (or
pdf@TeX{}) program, as it cannot support the fonts and thousands of
glyphs needed for these languages.

The Texinfo distribution comes with a couple of sample files that you
can use to test support for these languages:
@samp{short-sample-ja.texi} for Japanese, and @samp{short-sample-zh.texi}
for Chinese.

@cindex Xe@TeX{}
@cindex LuaTeX
For more information on these extensions to @TeX{}, see
@uref{https://tug.org/xetex/, the Xe@TeX{} home page} and
@uref{https://www.luatex.org/, the LuaTeX website}.


@node Generic Translator @command{texi2any}
@nodedescription @command{texi2any}, an all-purpose converter.
@chapter @command{texi2any}: The Translator for Texinfo

@command{texi2any} is the generic translator for Texinfo that can
produce different output formats and is highly customizable.  It
supports these formats:

@display
Info (by default, or with @option{--info}),
HTML (with @option{--html}),
EPUB 3 (with @option{--epub3}),
plain text (with @option{--plaintext}),
@LaTeX{} (with @option{--latex}),
DocBook (with @option{--docbook}).
@end display

@command{makeinfo} is an alias for @command{texi2any}.  By default,
both @command{texi2any} and @command{makeinfo} generate Info output;
indeed, there are no differences in behavior based on the name.

Beside these default formats, command line options to
@command{texi2any} can change many aspects of the output.  Beyond
that, initialization files provide even more control over the final
output---nearly anything not specified in the Texinfo input file.
Initialization files are written in Perl, and
anything which can be specified on the command line can also be
specified within a initialization file.

Two functionally equivalent implementations of @command{texi2any} can be built
in GNU Texinfo, one in Perl and another in compiled native code (in C).
The native code implementation is still experimental.
The Perl program can use Perl extension modules in compiled native code,
while the native code program embeds a Perl interpreter for the parts that
require Perl.
@c , mainly index sorting, most converter backends and HTML
@c customization.  The Perl program, when using native code backends is about as
@c fast as the main program in C using Perl when there is no native code
@c equivalent.

In the default case, the Perl implementation is installed.  You can select
the experimental C implementation instead at build time by passing
the @option{--enable-using-c-texi2any} option to @command{configure}.


@node Invoking @command{texi2any}
@nodedescription Running the translator from a shell.
@section Invoking @command{texi2any} from a Shell

@anchor{Invoking makeinfo}
@pindex makeinfo
@pindex texi2any

To process a Texinfo file, invoke @command{texi2any} followed by the name
of the Texinfo file.  Also select the format you want to output with the
appropriate command line option (default is Info).  Thus, to create
the Info file for Bison, type the following to the shell:

@example
texi2any --info bison.texi
@end example

You can specify more than one input file name; each is processed in
turn.  If an input file name is @samp{-}, standard input is read.

@anchor{@command{makeinfo} Options}
@c anchor{makeinfo options}@c prev name, but case-insensitive clash
@cindex @command{makeinfo} options
@cindex Options for @command{makeinfo}
@anchor{@command{texi2any} Options}
@cindex @command{texi2any} options
@cindex Options for @command{texi2any}

The @command{texi2any} program accepts many options.  Perhaps the
most basic are those that change the output format.  By default,
@command{texi2any} outputs Info.

Each command line option is either a long name preceded by @samp{--}
or a single letter preceded by @samp{-}.  You can use abbreviations
for the long option names as long as they are unique.

For example, you could use the following shell command to create an
Info file for @file{bison.texi} in which lines are filled to only
68 columns:

@example
texi2any --fill-column=68 bison.texi
@end example

You can write two or more options in sequence, like this:

@example
texi2any --no-split --fill-column=70 @dots{}
@end example

@noindent
(This would keep the Info file together as one possibly very long
file and would also set the fill column to 70.)

The options are (approximately in alphabetical order):

@table @code
@item --commands-in-node-names
@opindex --commands-in-node-names
This option now does nothing, but remains for compatibility.  (It used
to ensure that @@-commands in node names were expanded throughout the
document, especially @code{@@value}.  This is now done by default.)

@item --conf-dir=@var{dir}
@opindex --conf-dir=@var{dir}
Prepend @var{dir} to the directory search list for finding
customization files that may be loaded with @option{--init-file} (see
below).  The @var{dir} value can be a single directory, or a list of
several directories separated by the usual path separator character
(@samp{:} on Unix-like systems, @samp{;} on Windows). @c @xref{Loading
@c Init Files}.

@item --css-include=@var{file}
@opindex --css-include
When producing HTML, literally include the contents of @var{file},
which should contain Cascading Style Sheets specifications, in the
@samp{<style>} block of the HTML output.  If @var{file} is @samp{-},
read standard input.  @xref{HTML CSS}.

@item --css-ref=@var{url}
@opindex --css-ref
When producing HTML, add a @samp{<link>} tag to the output which
references a cascading style sheet at @var{url}.  This allows using
standalone style sheets.

@item -D @var{var}
@itemx -D '@var{var} @var{value}'
@opindex -D @var{var}
Cause the Texinfo variable @var{var} to be defined.  This is
equivalent to @code{@@set @var{var}} in the Texinfo file
(@pxref{@code{@@set @@clear @@value}}).

The argument to the option is always one word to the shell; if it
contains internal whitespace, the first word is taken as the variable
name and the remainder as the value.  For example, @code{-D 'myvar
someval'} is equivalent to @code{@@set myvar someval}.

@item --docbook
@opindex --docbook
Generate DocBook output (rather than Info).

@item --document-language=@var{lang}
@opindex --document-language
Use @var{lang} as main language to translate Texinfo keywords which
end up in the output document.  The default is the language specified by the
@code{@@documentlanguage} command if there is one, otherwise English
strings are output (@pxref{Setting the language}).

@item --dvi
@opindex --dvi
Generate a TeX DVI file using @command{texi2dvi}, rather than Info
(@pxref{@command{texi2any} Printed Output}).

@item --dvipdf
@opindex --dvipdf
Generate a PDF file using @command{texi2dvi --dvipdf}, rather than
Info (@pxref{@command{texi2any} Printed Output}).

@item --enable-encoding
@itemx --disable-encoding
@opindex --enable-encoding
@opindex --disable-encoding
@c @vindex ENABLE_ENCODING
By default, or with @option{--enable-encoding}, output accented and
special characters in Info and plain text output based on
the document encoding.  With @option{--disable-encoding}, 7-bit
ASCII transliterations are output.  Also obeyed in other output
formats for index keys sorting and for some plain text output.

@item --epub3
@opindex --epub3
Generate EPUB 3 output.

@item --error-limit=@var{limit}
@itemx -e @var{limit}
@opindex --error-limit=@var{limit}
@opindex -e @var{limit}
@c @vindex ERROR_LIMIT
Report @var{limit} errors before aborting (on the assumption that
continuing would be useless); default 100.

@item --fill-column=@var{width}
@itemx -f @var{width}
@opindex --fill-column=@var{width}
@opindex -f @var{width}
@c @vindex FILLCOLUM
Specify the maximum number of columns in a line; this is the
right-hand edge of a line.  Paragraphs that are filled will be filled
to this width.  (Filling is the process of breaking up and connecting
lines so that lines are the same length as or shorter than the number
specified as the fill column.  Lines are broken between words.) The
default value is 72.

@item --footnote-style=@var{style}
@itemx -s @var{style}
@opindex --footnote-style=@var{style}
@opindex -s @var{style}
@vindex footnotestyle
Set the footnote style to @var{style}: either @samp{end} for the end
node style (the default) or @samp{separate} for the separate node
style.  The value set by this option overrides the value set in a
Texinfo file by a @code{@@footnotestyle} command (@pxref{Footnote
Styles}).

In Info, when the footnote style is @samp{separate}, @command{texi2any} makes a
new node containing the footnotes found in the current node.  When the
footnote style is @samp{end}, @command{texi2any} places the footnote
references at the end of the current node.

In HTML, when the footnote style is @samp{end}, or if the output is
not split, footnotes are put at the end of the output.  If set to
@samp{separate}, and the output is split, they are placed in a
separate file.

@item --force
@itemx -F
@opindex --force
@opindex -F
@c @vindex FORCE
Ordinarily, if the input file has errors, the output files are not
created.  With this option, they are preserved.

@item --help
@itemx -h
@opindex --help@r{, for @command{texi2any}}
@opindex -h
Print a message with available options and basic usage, then exit
successfully.

@item --html
@opindex --html
Generate HTML output (rather than Info).  By default, the HTML output
is split into one output file per node, and the split output is written
into a subdirectory based on the name of the input file.
@xref{Generating HTML}.

@item -I @var{dir}
@opindex -I @var{dir}
Append @var{dir} to the directory search list for finding files that
are included using the @code{@@include} command.  By default,
@command{texi2any} searches the current directory and the input file
path leading directory if there is one (and it is not the current directory).
The @var{dir} value can be a single directory or a list of several
directories separated by the usual path separator character (@samp{:} on
Unix-like systems, @samp{;} on Windows).

@item --ifdocbook
@opindex --ifdocbook
@item --ifepub
@opindex --ifepub
@itemx --ifhtml
@opindex --ifhtml
@itemx --ifinfo
@opindex --ifinfo
@itemx --iflatex
@opindex --iflatex
@itemx --ifplaintext
@opindex --ifplaintext
@itemx --iftex
@opindex --iftex
For the given format, process @samp{@@if@var{format}} and
@samp{@@@var{format}} commands, and do not process
@samp{@@ifnot@var{format}}, regardless of the format being output.
For instance, if @option{--iftex} is given, then @samp{@@iftex} and
@samp{@@tex} blocks will be read, and @samp{@@ifnottex} blocks will be
ignored.

@item --no-ifdocbook
@opindex --no-ifdocbook
@item --no-ifepub
@opindex --no-ifepub
@itemx --no-ifhtml
@opindex --no-ifhtml
@itemx --no-ifinfo
@opindex --no-ifinfo
@itemx --no-iflatex
@opindex --no-iflatex
@itemx --no-ifplaintext
@opindex --no-ifplaintext
@itemx --no-iftex
@opindex --no-iftex
For the given format, do not process @samp{@@if@var{format}} and
@samp{@@@var{format}} commands, and do process
@samp{@@ifnot@var{format}}, regardless of the format being output.
For instance, if @option{--no-ifhtml} is given, then @samp{@@ifhtml}
and @samp{@@html} blocks will not be read, and @samp{@@ifnothtml}
blocks will be.


@item --info
@opindex --info
Generate Info output.  By default, if the output file contains more
than about 300,000 bytes, it is split into shorter subfiles of about
that size.  The name of the output file and any subfiles is determined
by the input file name, or by @code{@@setfilename}, if present
(@pxref{Setting the Output File Name}).  @xref{Tag and Split Files}.

@item --init-file=@var{file}
@opindex --init-file=@var{file}
Load @var{file} as code to modify the behavior and output of the
generated manual.  It is customary to use the @code{.pm} or the
@code{.init} extensions for these customization files, but that is not
enforced; the @var{file} name can be anything.  The
@option{--conf-dir} option (see above) can be used to add to the list
of directories in which these customization files are searched for.
@c @xref{Loading Init Files}.

@item --internal-links=@var{file}
@opindex --internal-links=@var{file}
@cindex Internal links, of HTML
@c @vindex INTERNAL_LINKS
In HTML mode, output a tab-separated file containing three columns:
the internal link to an item, the type of the item and the name of the item
or the term corresponding to the item which was indexed or entered.

The items output are:
@table @asis
@item output units
Output units are the main unit of output documents.  Output units contain the
content associated with a node or a sectioning command.  The item name is
the associated node or a sectioning command name.
@item sectioning commands
The command name without @code{@@}, adjusted for raise/lowersections is
prepended to the item name.
@item nodes, anchors and floats
The type of the element is the command name without @code{@@}.
@item index entries
The type of the element is the name of the index.
@end table

The items are in the natural
sorting order for the given element.  This dump can be useful for
post-processors.

@item --latex
@opindex --latex
Generate @LaTeX{} output.

@item --macro-expand=@var{file}
@itemx -E @var{file}
@opindex --macro-expand=@var{file}
@opindex -E @var{file}
@c @vindex MACRO_EXPAND
Output the Texinfo source, with all Texinfo macros expanded, to
@var{file}.  Normally, the result of macro expansion is used
internally by @command{texi2any} and then discarded.

@item --no-headers
@opindex --no-headers
@cindex Node separators, omitting with @option{--no-headers}
@cindex Generating plain text files with @option{--no-headers}
@cindex Menus, omitting with @option{--no-headers}
@c @vindex HEADERS
Do not include menus or node separator lines in the output.

When generating Info, this is the same as using @option{--plaintext},
resulting in a simple plain text file.  Furthermore, output is
to standard output unless overridden with @option{-o}.  (This
behavior is for backward compatibility.)

@cindex Navigation links, omitting
When generating HTML, and output is split, also output navigation
links only at the beginning of each file.  If output is not split, do
not include navigation links at the top of each node at all.
@xref{Generating HTML}.

@item --node-files
@itemx --no-node-files
@opindex --node-files
@opindex --no-node-files
@c @vindex NODE_FILES
@anchor{@option{--node-files}}
With @option{--node-files}, when generating HTML, create redirection
files for anchors and any nodes not already output with the file name
corresponding to the node name (@pxref{HTML Xref Node Name Expansion}).
This makes it possible for section- and chapter-level cross-manual
references to succeed (@pxref{HTML Xref Configuration}).

If the output is split, this is enabled by default.  If the output is
not split, @option{--node-files} enables the creation of the
redirection files, in addition to the monolithic main output file.
@option{--no-node-files} suppresses the creation of redirection files
in any case.  This option has no effect with any output format other
than HTML@.  @xref{Generating HTML}.

@item --no-validate
@itemx --no-pointer-validate
@opindex --no-validate
@opindex --no-pointer-validate
@cindex Pointer validation
@anchor{Pointer Validation}@c
Suppress the pointer-validation phase of @command{texi2any}---a dangerous
thing to do.  This can also be done with the @code{@@novalidate}
command (@pxref{Formatting Partial Documents}).

If you do not suppress pointer validation, @command{texi2any} will check
the validity of cross-references and menu entries in the Texinfo file, as
well as node pointers if they are given explicitly.

@ignore @c TODO this may not be accurate
If node pointers are implicitly determined, @command{texi2any} checks
that the tree constructed from the document's menus matches the
tree constructed from the sectioning commands.  For example, if a
chapter-level menu mentions nodes @var{n1} and @var{n2}, in that order,
nodes @var{n1} and @var{n2} must be associated with @code{@@section}
commands in the chapter.

If node pointers are explicitly determined, here is the list of what
is checked:

@enumerate
@item
If a `Next', `Previous', or `Up' node reference is a reference to a
node in the current file and is not an external reference such as to
@file{(dir)}, then the referenced node must exist.

@item
Every node except the `Top' node must have an `Up' pointer.

@item
The node referenced by an `Up' pointer must itself reference the
current node through a menu item, unless the node referenced by `Up'
has the form @samp{(@var{file})}.
@end enumerate
@end ignore

@item --no-warn
@opindex --no-warn
@c @vindex NO_WARN
Suppress warning messages (but not error messages).

@item --number-footnotes
@itemx --no-number-footnotes
@opindex --no-number-footnotes
@c @vindex NUMBER_FOOTNOTES
With @option{--no-number-footnotes}, suppress automatic footnote
numbering.  By default, footnotes are numbered sequentially within a node,
i.e., the current footnote number is reset to 1 at the start of each node.

@item --number-sections
@itemx --no-number-sections
@opindex --number-sections
@opindex --no-number-sections
@c @vindex NUMBER_SECTIONS
With @option{--number-sections} (the default), output chapter,
section, and appendix numbers as in printed manuals.  This works only
with hierarchically structured manuals.  You should specify
@code{--no-number-sections} if your manual is not normally structured.


@item --output=@var{file}
@itemx -o @var{file}
@opindex --output=@var{file}
@opindex -o @var{file}
@c @vindex OUTFILE
@c @vindex SUBDIR
Specify that the output should be directed to @var{file}.  This
overrides any file name specified in a @code{@@setfilename} command
found in the Texinfo source.  If neither @code{@@setfilename} nor this
option are specified, the input file name is used to determine the
output name.  @xref{Setting the Output File Name}.

If @var{file} is @samp{-}, output goes to standard output and
@samp{--no-split} is implied.

If @var{file} is a directory or ends with a @samp{/} the usual rules
are used to determine the output file name (namely, use
@code{@@setfilename} or the input file name) but the files are written
to the @var{file} directory.  For example, @samp{texi2any -o bar/
foo.texi}, with or without @option{--no-split}, will write
@file{bar/foo.info}, and possibly other files, under @file{bar/}.

When generating HTML and output is split, @var{file} is used as the
name for the directory into which all files are written.  For example,
@samp{texi2any -o bar --html foo.texi} will write
@file{bar/index.html}, among other files.

When generating EPUB a container directory for the files and directories needed
for the EPUB format is created, as well as the EPUB output file.  If @var{file}
corresponds to a directory, the container directory is placed within @var{file}.
The EPUB output file is never put in this directory.  If @var{file} corresponds
to a file, it is used for the EPUB output file name.

@item --output-indent=@var{val}
@opindex --outputindent
This option now does nothing, but remains for compatibility.  (It used
to alter indentation in XML-based formats such as DocBook output.)

@item -P @var{path}
@opindex -P @var{path}
Prepend @var{path} to the directory search list for @code{@@include}.
See @samp{-I} above.

@item --paragraph-indent=@var{indent}
@itemx -p @var{indent}
@opindex --paragraph-indent=@var{indent}
@opindex -p @var{indent}
Set the paragraph indentation style to @var{indent}.  The value set by
this option overrides the value set in a Texinfo file by an
@code{@@paragraphindent} command (@pxref{@code{@@paragraphindent}}).
The value of @var{indent} is interpreted as follows:

@table @asis
@item @samp{asis}
Preserve any existing indentation (or lack thereof) at the beginnings
of paragraphs.

@item @samp{0} or @samp{none}
Delete any existing indentation.

@item @var{num}
Indent each paragraph by @var{num} spaces.
@end table

The default is to indent by two spaces, except for paragraphs
following a section heading, which are not indented.

@item --pdf
@opindex --pdf
Generate a PDF file using @command{texi2dvi --pdf}, rather than Info
(@pxref{@command{texi2any} Printed Output}).

@item --plaintext
@opindex --plaintext
@cindex Plain text output with @option{--plaintext}
@cindex ASCII text output with @option{--plaintext}
@cindex Generating plain text files with @option{--plaintext}
@cindex Node separators, omitting with @option{--plaintext}
@cindex Menus, omitting with @option{--plaintext}
@cindex @file{INSTALL} file, generating
Output a plain text file (rather than Info): do not include menus or
node separator lines in the output.  This results in a straightforward
plain text file that you can (for example) send in email without
complications, or include in a distribution (for example, an
@file{INSTALL} file).

With this option the output goes to standard output by default, instead
of to a file with a name based on the input file name or @code{@@setfilename};
this can be overridden with @option{-o}.

@item --ps
@opindex --ps
Generate a PostScript file using @command{texi2dvi --ps}, rather than
Info (@pxref{@command{texi2any} Printed Output}).

@item --set-customization-variable @var{var}=@var{value}
@itemx -c @var{var}=@var{value}
@opindex --set-customization-variable @var{var}=@var{value}
@opindex -c @var{var}=@var{value}
Set the customization variable @var{var} to @var{value}.  The @code{=}
is optional, but both @var{var} and @var{value} must be quoted to the
shell as necessary so the result is a single word.  Many aspects of
@command{texi2any} behavior and output may be controlled by
customization variables, beyond what can be set in the document by
@@-commands and with other command line switches.  @xref{Customization
Variables}.

@item --split=@var{how}
@itemx --no-split
@opindex --split=@var{how}
@opindex --no-split
@cindex Splitting of output files
@cindex Output file splitting
@anchor{Splitting Output}
@c
When generating Info, by default large output files are split into
smaller subfiles, of approximately 300k bytes.  When generating HTML,
by default each output file contains one node (@pxref{Generating
HTML}).  @option{--no-split} suppresses this splitting of the output.

@c @vindex SPLIT
Alternatively, @option{--split=@var{how}} may be used to specify at
which level the HTML output should be split.  The possible values for
@var{how} are:

@table @samp
@item chapter
The output is split at @code{@@chapter} and other sectioning
@@-commands at this level (@code{@@appendix}, etc.).

@item section
The output is split at @code{@@section} and similar.

@item node
The output is split at every node.  This is the default.
@end table

Plain text output can be split similarly to HTML@.  This may be useful
for extracting sections from a Texinfo document and making them
available as separate files.

@item --split-size=@var{num}
@opindex --split-size=@var{num}
@c @vindex SPLIT_SIZE
Keep Info files to at most @var{num} characters if possible; default
is 300,000.  (However, a single node will never be split across Info
files.)

@item --trace-includes
@opindex --trace-includes
@c @vindex TRACE_INCLUDES
Print the name of each included file to standard output, including any
indirectly included files.  An include file is printed only if it was
actually found.  When this option is given, @command{texi2any} does not
output in any output format.  (The purpose of this option is to make it
easier to collect the sources of a Texinfo manual.)

@item --transliterate-file-names
@opindex --transliterate-file-names
@c @vindex TRANSLITERATE_FILE_NAMES
Enable transliteration of non-ASCII characters in node and sectioning commands
names for the purpose of file name and sectioning commands identifiers
creation.  The file names and identifiers obtained that way are platform and
processor dependent.  @xref{HTML Xref 8-bit Character Expansion}.

Redirection files for anchors and nodes are not affected, therefore if
@option{--node-files} is enabled, files with non-transliterated names are
created too.  It is recommended to have non-translitered file names
created for nodes such that cross-references to the generated manual
succeed.  @xref{@option{--node-files}}. @xref{HTML Xref Configuration}.

@item -U @var{var}
Cause @var{var} to be undefined.  This is equivalent to @code{@@clear
@var{var}} in the Texinfo file (@pxref{@code{@@set @@clear @@value}}).

@item --verbose
@opindex --verbose
@c @vindex VERBOSE
Cause @command{texi2any} to display messages saying what it is doing.
Normally, @command{texi2any} only outputs messages if there are errors or
warnings.

@item --version
@itemx -V
@opindex --version@r{, for @command{texi2any}}
@opindex -V
Print the version number, then exit successfully.

@item --Xopt @var{str}
@opindex --Xopt @var{str}
Pass @var{str} (a single shell word) to @command{texi2dvi}; may be
repeated (@pxref{@command{texi2any} Printed Output}).

@end table


@node @command{texi2any} Environment Variables
@nodedescription Control over output format and XS use.
@section Environment Variables Recognized by @command{texi2any}

@cindex Environment variable @code{TEXINFO_OUTPUT_FORMAT}
@command{texi2any} also reads the environment variable
@env{TEXINFO_OUTPUT_FORMAT} to determine the output format, if not
overridden by a command line option.  The value should be one of:

@example
docbook  dvi  dvipdf  epub3  html  info  latex  pdf  plaintext  ps
@end example

If not set or otherwise specified, Info output is the default.

@code{TEXINFO_OUTPUT_FORMAT} may take some other special values, which do
not correspond to any command-line settable output format
(@pxref{Output Format Selection}).

The customization variable of the same name is also read; if set, that
overrides an environment variable setting, but not a command-line
option.  @xref{Output Format Selection}.

@vindex TEXINFO_XS
@cindex Perl extension modules (XS)
You can control the Perl @command{texi2any} implementation's use of Perl
extension modules by setting the @env{TEXINFO_XS} environment variable.
These modules are compiled native code that the interpreted Perl code can use.
Ideally, these extension modules should just work, and the only noticeable
difference they should make is that @command{texi2any} finishes running
sooner.  However, you can use this environment variable for the purposes
of troubleshooting: for example, if you have problems with the output of
@command{texi2any} varying depending on whether the extension modules are
in use.

The following values of @env{TEXINFO_XS} are recognized by
@command{texi2any}:

@table @samp
@item default
The default behavior.  Try to load extension modules enabled at
build time.  Abort if an extension module fails to load.

@item debug
Same as default, printing many messages while loading extension
modules.

@item omit
Do not use extension modules.
@end table

The C @command{texi2any} implementation always try to load Perl extension
modules when calling interpreted Perl code and aborts if an extension
cannot be loaded.  Setting @env{TEXINFO_XS} to @code{omit} with the C
@command{texi2any} implementation is an error and is ignored.

@c this environment variable is likely to be removed, so do not document
@c it here.
@ignore
@vindex TEXINFO_C_EMBED_PERL
@cindex Embedded Perl in C @command{texi2any}
You can control the C @command{texi2any} implementation's use of embedded
Perl, by setting the @env{TEXINFO_C_EMBED_PERL} environment variable to
@samp{0} to disable the use of embedded Perl.  Set with care, as HTML
customization initialization files, conversion to most output formats and
optimal index sorting require Perl.
@end ignore


@node @command{texi2any} Printed Output
@nodedescription Calling @command{texi2dvi}.
@section @command{texi2any} Printed Output

@cindex Printed output, through @command{texi2any}
@cindex Output, printed through @command{texi2any}

To justify the name Texinfo-to-@emph{any}, @command{texi2any} has
basic support for creating printed output in the various formats:
@TeX{} DVI, PDF, and PostScript.  This is done via the simple method
of executing the @command{texi2dvi} program when those output formats
are requested, after checking the validity of the input to give users
the benefit of @command{texi2any}'s error checking.  If you don't want
such error checking, perhaps because your manual plays advanced @TeX{}
tricks together with @file{texinfo.tex}, just invoke
@command{texi2dvi} directly.

The output format options for this are @option{--dvi},
@option{--dvipdf}, @option{--pdf}, and @option{--ps}.  @xref{Format
with @command{texi2dvi}}, for more details on these options and general
@command{texi2dvi} operation.  In addition, the @option{--verbose},
@option{--silent}, and @option{--quiet} options are passed on if
specified; the @option{-I} and @option{-o} options are likewise passed
on with their arguments, and @option{--debug} without its argument.

The only option remaining that is related to the @command{texi2dvi}
invocation is @option{--Xopt}.  Here, just the argument is passed on
and multiple @option{--Xopt} options accumulate.  This provides a way
to construct an arbitrary command line for @command{texi2dvi}.  For
example, running

@example
texi2any --Xopt -t --Xopt @@afourpaper --pdf foo.texi
@end example

@noindent is equivalent to running

@example
texi2dvi -t @@afourpaper --pdf foo.texi
@end example

@noindent except for the validity check.

Although one might wish that other options to @command{texi2any} would
take effect, they don't.  For example, running @samp{texi2any
--no-number-sections --dvi foo.texi} still results in a DVI file with
numbered sections.  (Perhaps this could be improved in the future, if
requests are received.)

The actual name of the command that is invoked is specified by the
@code{TEXI2DVI} customization variable (@pxref{Customization Variables for
Multiple Formats}).  As you might guess, the default is @samp{texi2dvi}.

@command{texi2any} itself does not generate any normal output when it
invokes @command{texi2dvi}, only diagnostic messages.


@node Customization Variables
@nodedescription Configuring @command{texi2any}.
@section Customization Variables

@quotation Warning
These customization variable names and meanings may change in any
Texinfo release.  We always try to avoid incompatible changes, but we
cannot absolutely promise, since needs change over time.
@end quotation

Many aspects of the behavior and output of @command{texi2any} may be
modified by modifying so-called @dfn{customization variables}.  These
fall into a few general categories:

@itemize @bullet
@item
Those associated with @@-commands; for example,
@code{@@documentlanguage}.

@item
Those associated with command-line options; for example, the
customization variable @code{SPLIT} is associated with the
@option{--split} command-line option. @code{TEXINFO_OUTPUT_FORMAT}
is set based on output format command line options and
allows specifying the output format.

@item
Those affecting the global behavior of @command{texi2any}, in particular
Texinfo code parsing.

@item
Those associated with particular output formats.
(Variables only relevant for HTML output are documented in @ref{HTML
Output Customization}.)

@item
Those relevant for multiple output formats.
@end itemize

You may set customization variables on the command line using
@code{--set-customization-variable '@var{var} @var{value}'} (quoting
the variable/value pair to the shell) or
@code{--set-customization-variable @var{var}=@var{value}} (using
@code{=}).  A special @var{value} is @samp{undef}, which sets the
variable to this special ``undefined'' Perl value.

The sections below give the details for each of these.

@menu
* Commands: Customization Variables for @@-Commands.
* Options:  Customization Variables and Options.
* Format:   Output Format Selection.
* Global:   Global Customization Variables.
* Info:     Info and Plaintext Customization Variables.
* LaTeX:    @LaTeX{} Customization Variables.
* Other:    Other Formats Customization Variables.
* Formats:  Customization Variables for Multiple Formats.
@end menu


@node Customization Variables for @@-Commands
@subsection Customization Variables for @@-Commands

@cindex Customization variables for @@-commands
@cindex @sortas{at} @@-commands @subentry customization variables for

Each of the following @@-commands has an associated customization
variable with the same name (minus the leading @code{@@}):

@example
@@afivepaper            @@afourpaper        @@afourlatex
@@afourwide             @@allowcodebreaks   @@bsixpaper
@@contents              @@codequotebacktick
@@codequoteundirected   @@deftypefnnewline  @@documentdescription
@@documentencoding      @@documentlanguage  @@documentscript
@@evenfooting           @@evenfootingmarks  @@evenheading
@@evenheadingmarks      @@everyfooting      @@everyfootingmarks
@@everyheading          @@everyheadingmarks
@@exampleindent         @@firstparagraphindent
@@fonttextsize          @@footnotestyle     @@frenchspacing
@@headings              @@kbdinputstyle     @@microtype
@@novalidate            @@oddfooting        @@oddfootingmarks
@@oddheading            @@oddheadingmarks   @@pagesizes
@@paragraphindent       @@setfilename       @@setchapternewpage
@@shortcontents         @@smallbook         @@summarycontents
@@urefbreakstyle        @@xrefautomaticsectiontitle
@end example

Setting such a customization variable to a value @samp{foo} is similar
to executing @code{@@@var{cmd} foo}.  It is not exactly the same,
though, since any side effects of parsing the Texinfo source are not
redone.  Also, some variables do not take Texinfo code when generating
particular formats, but an argument that is already formatted.  This
is the case, for example, for HTML for @code{documentdescription}.

Note that if @command{texi2any} is invoked to process the file with
@TeX{} (e.g., with the @option{--pdf} option), then these customization
variables may not be passed on to @TeX{}.


@node Customization Variables and Options
@subsection Customization Variables and Options

@cindex Customization variables for options
@cindex Options, customization variables for

The following table gives the customization variables associated with
some command line options.  @xref{Invoking @command{texi2any}}, for the
meaning of the options.

@multitable @columnfractions 0.5 0.5
@headitem Option @tab Variable
@item
@vindex ENABLE_ENCODING
@option{--enable-encoding}   @tab @code{ENABLE_ENCODING}
@item
@option{--document-language} @tab @code{documentlanguage}
@item
@vindex ERROR_LIMIT
@option{--error-limit}       @tab @code{ERROR_LIMIT}
@item
@vindex FILLCOLUMN
@option{--fill-column}       @tab @code{FILLCOLUMN}
@item
@option{--footnote-style}    @tab @code{footnotestyle}
@item
@vindex FORCE
@option{--force}             @tab @code{FORCE}
@item
@vindex HEADERS
@option{--headers}           @tab @code{HEADERS}, @code{FORMAT_MENU}
@item
@vindex INTERNAL_LINKS
@option{--internal-links}    @tab @code{INTERNAL_LINKS}
@item
@vindex MACRO_EXPAND
@option{--macro-expand}      @tab @code{MACRO_EXPAND}
@item
@vindex novalidate
@option{--no-validate}       @tab @code{novalidate}
@item
@vindex NO_WARN
@option{--no-warn}           @tab @code{NO_WARN}
@item
@vindex NODE_FILES
@option{--node-files}        @tab @code{NODE_FILES}
@item
@vindex NUMBER_FOOTNOTES
@option{--number-footnotes}  @tab @code{NUMBER_FOOTNOTES}
@item
@vindex NUMBER_SECTIONS
@option{--number-sections}   @tab @code{NUMBER_SECTIONS}
@item
@vindex OUTFILE
@vindex SUBDIR
@option{--output}            @tab @code{OUTFILE}, @code{SUBDIR}
@item
@vindex paragraphindent
@option{--paragraph-indent}  @tab @code{paragraphindent}
@item
@vindex SPLIT
@option{--split}             @tab @code{SPLIT}
@item
@vindex SPLIT_SIZE
@option{--split-size}        @tab @code{SPLIT_SIZE}
@item
@vindex TRACE_INCLUDES
@option{--trace-includes}    @tab @code{TRACE_INCLUDES}
@item
@vindex TRANSLITERATE_FILE_NAMES
@option{--transliterate-file-names} @tab @code{TRANSLITERATE_FILE_NAMES}
@item
@vindex VERBOSE
@option{--verbose}           @tab @code{VERBOSE}
@end multitable

Setting such a customization variable to a value @samp{foo} is
essentially the same as specifying the @code{--@var{opt}=foo} if the
option takes an argument, or @code{--@var{opt}} if not.


@node Output Format Selection
@subsection Output Format Selection

@c @vindex TEXINFO_OUTPUT_FORMAT
The customization variable @code{TEXINFO_OUTPUT_FORMAT} takes the
value of the format output by @command{texi2any}.  This can be one of
the usual output formats that can be specified with options, or various
other special output formats:

@table @samp
@item docbook
@itemx dvi
@itemx dvipdf
@itemx epub3
@itemx html
@itemx info
@itemx pdf
@itemx plaintext
@itemx ps
These correspond to the command-line options (and
@code{TEXINFO_OUTPUT_FORMAT} environment variable values) of the same
name.  The @code{TEXINFO_OUTPUT_FORMAT} customization variable value
is set when command-line options (or @code{TEXINFO_OUTPUT_FORMAT}
environment variable values) set the output format.
@xref{Invoking @command{texi2any}}.

@cindex tree representation, for debugging
@cindex debugging document, with tree representation
@item debugtree
Instead of generating a regular output format, output a text representation
of the tree obtained by parsing the input texinfo document.

@item parse
Do only Texinfo source parsing; there is no output.

@item plaintexinfo
Output the Texinfo source with all the macros, @code{@@include} and
@code{@@value@{@}} expanded.  This is similar to setting
@option{--macro-expand}, but instead of being output in addition to
the normal conversion, output of Texinfo is the main output.

@cindex raw text output
@item rawtext
Output raw text, with minimal formatting.  For example, footnotes are
ignored and there is no paragraph filling.  This is used by the parser
for file names and copyright text in HTML comments, for example.

@item structure
Do only Texinfo source parsing and determination of the document
structure; there is no output.

@cindex SXML output
@cindex S-expressions, output format
@item texinfosxml
Output the document in TexinfoSXML representation, a syntax for
writing XML data using Lisp S-expressions.  This output format
is deprecated and will be removed in a future release.

@cindex XML Texinfo output
@item texinfoxml
Output the document in Texinfo XML representation.  This output format
is deprecated and will be removed in a future release.

@cindex spell checking
@cindex word counting
@pindex detexinfo
@cindex stripping Texinfo commands
@item textcontent
Output the text content only, stripped of commands; this is useful for
spell checking or word counting, for example.  The trivial
@code{detexinfo} script setting this is in the @file{util} directory
of the Texinfo source as an example.  It's one line:

@example
exec texi2any -c TEXINFO_OUTPUT_FORMAT=textcontent "$@@"
@end example
@end table


@node Global Customization Variables
@subsection Global Customization Variables

This table gives the customization variables which affect the global behavior
of @command{texi2any}.

@vtable @code
@item CHECK_MISSING_MENU_ENTRY
When a @code{@@menu} block occurs in a node, check if there is a menu
entry for all subordinate nodes in the document sectioning structure.  On
by default.

@item CHECK_NORMAL_MENU_STRUCTURE
Warn if the node pointers (either explicitly or automatically set)
are not consistent with the order of node menu entries.  This is a more
thorough structure check than that provided by
@code{CHECK_MISSING_MENU_ENTRY}.  On by default.

@item COLLATION_LANGUAGE
By default, @command{texi2any} sorts document indices according to the
@dfn{Unicode Collation Algorithm} (defined in
@uref{http://www.unicode.org/reports/tr10/, Unicode Technical Standard #10}),
without language-specific collation tailoring.  If set, use the language
for linguistic tailoring of index sorting.

Currently, @command{texi2any} gives no warning if there is no support
for linguistic tailoring due to either missing software or missing
support for the specified language.

In Perl, the @code{Unicode::Collate::Locale} module is used for linguistic
tailoring; therefore if this module is not installed, the variable will be
silently ignored.

If @code{USE_UNICODE_COLLATION} is set to @samp{0}, there is no Unicode
collation and so no linguistic tailoring either.

See also the @code{DOCUMENTLANGUAGE_COLLATION} variable, described below.

@item COMMAND_LINE_ENCODING
Encoding used to decode and encode command-line arguments.  Default is based on
the locale encoding.  This may affect file names inserted into output files or
error messages printed by the program.

Note that some file and directory names from the command line may
not be decoded immediately, and may not be decoded at all.

It is also used to encode command-line argument passed to commands called from
@command{texi2any}.  For example, @command{latex2html} will be called from
@command{texi2any} if @code{HTML_MATH} is set to @samp{l2h}.

@item CPP_LINE_DIRECTIVES
Recognize @code{#line} directives in a ``preprocessing'' pass
(@pxref{External Macro Processors}); on by default.

@item DEBUG
If set, debugging output is generated; default is off (zero).
@c The integer value specifies what kinds of debugging output are
@c generated.  It is a bitmask.  Setting it to 255 ensures having all
@c available debugging output.

@item DOC_ENCODING_FOR_INPUT_FILE_NAME
If set, use the input Texinfo document encoding information for
the encoding of input file names, such as file names specified as
@code{@@include} or @code{@@verbatiminclude} arguments.  If unset, use
the locale encoding instead.  Default is set, except on MS-Windows where
the locale encoding is used by default.

Note that this is for file names only; the default encoding or
@code{@@documentencoding} is always used for the encoding of file
content (@pxref{@code{@@documentencoding}}).

The @code{INPUT_FILE_NAME_ENCODING} variable overrides this variable.

@item DOC_ENCODING_FOR_OUTPUT_FILE_NAME
If set, use the input Texinfo document encoding information for the
encoding of output file names, such as files specified with @option{--output}.
If unset, use the locale encoding instead.  Default is unset, so files
names are encoded using the current locale.

Note that this is for file names only; @code{OUTPUT_ENCODING_NAME}
is used for the encoding of file content.

The @code{OUTPUT_FILE_NAME_ENCODING} variable overrides this variable.

@item DOCUMENTLANGUAGE_COLLATION
If set, try to use the language specified in a @code{@@documentlanguage}
(and @code{@@documentscript}) directive for language-specific tailoring of
index sorting.  See also the @code{COLLATION_LANGUAGE} variable, described
above.  (@xref{Setting the language}.)

@item DUMP_STRUCTURE
For debugging.  If set, the tree constructed upon parsing a Texinfo
document and determining the document structure is output to the file;
if set to @samp{-} output to standard error.  Default false.

@item DUMP_TEXI
For debugging.  If set, no conversion is done, only parsing and macro
expansion.  If the option @option{--macro-expand} is set, the Texinfo
source is also expanded to the corresponding file.  Default false.

@item DUMP_TREE
For debugging.  If set, the tree constructed upon parsing a Texinfo
document is output to the file; if set to @samp{-} output to standard error.
Default false.

@item FORMAT_MENU
If set to @samp{menu}, output Texinfo menus.  This is the default for
Info.  @samp{sectiontoc} is the default setting for HTML, where instead
of the contents of @code{@@menu} blocks being output, a list of subordinate
sections is output in each node.  Set to @samp{menu_no_detailmenu} instead
of @samp{menu} in HTML if you want menus but no automatically generated
@code{@@detailmenu} in the Top node master menu.  If set to
@samp{nomenu}, do not output menus.

This variable is set to @samp{nomenu} when generating DocBook, or when
@option{--no-headers} is specified.

@c document?
@ignore
@item HANDLER_FATAL_ERROR_LEVEL
This variable sets the error level above which errors returned by
user defined functions registered to be called at different stages
are considered to be fatal errors.  You should not need to change this
value.  Default 100.
@end ignore

@item IGNORE_SPACE_AFTER_BRACED_COMMAND_NAME
If set, spaces are ignored after an @@-command that takes braces.
Default true, matching the @TeX{} behavior.

@cindex Encoding @subentry input file names
@item INPUT_FILE_NAME_ENCODING
Encoding used for input file names.  This variable overrides
any encoding from the document or current locale.  Normally, you do
not need to set this variable, but it can be used if file names are
in a certain character encoding on a filesystem.  An alternative is to
set @code{DOC_ENCODING_FOR_INPUT_FILE_NAME} to @samp{0} to use the locale
encoding.  See also @code{OUTPUT_FILE_NAME_ENCODING}.

@item LOCALE_ENCODING
Locale encoding obtained from the system.  You should not need to
explicitly set this variable.

@item MAX_MACRO_CALL_NESTING
The maximal number of recursive calls of @@-commands defined through
@code{@@rmacro}; default 100000.  The purpose of this variable is to
avoid infinite recursions.

@item MESSAGE_ENCODING
Encoding used to encode messages output by @command{texi2any}.  Default is
based on the locale encoding.

@item NO_INDEX
If set, index entries are not recorded and @@-commands related to
indices, such as @code{@@printindex}, @code{@@synindex} or @code{@@defindex}
have no effect.  Default false.

@item NO_USER_COMMANDS
If set, definitions of user-defined @@-command are ignored.  @code{@@alias},
@code{@@definfoenclose}, @code{@@defindex}, @code{@@macro} and similar
@@-commands have no effect.  Default false.

@item OUTPUT_ENCODING_NAME
Normalized encoding name used for output files.  Should be a usable
charset name in HTML, typically one of the preferred IANA encoding
names.  By default, if an input encoding is set (typically through
@code{@@documentencoding}), this information is used to set the output
encoding name, otherwise the output encoding is based on the
default encoding.  @xref{@code{@@documentencoding}}.

@cindex Encoding @subentry output file names
@item OUTPUT_FILE_NAME_ENCODING
Encoding used for output file names.  This variable overrides
any encoding from the document or current locale.

Normally, you do not need to set this variable, but it can be used if file
names should be created in a certain character encoding on a filesystem.
See also @code{INPUT_FILE_NAME_ENCODING}.

@item PACKAGE
@itemx PACKAGE_VERSION
@itemx PACKAGE_AND_VERSION
@itemx PACKAGE_URL
@itemx PACKAGE_NAME
The implementation's short package name, package version, package name
and version concatenated, package URL@:, and full package name,
respectively.  By default, these variables are all set through
Autoconf, Automake, and @code{configure}.

@item PREFIX
The output file prefix, which is prepended to some output file names.
By default it is set by @code{@@setfilename} or from the input file
(@pxref{Setting the Output File Name}).  How this value is used depends on the
value of other customization variables or command line options, such
as whether the output is split.  The default is unset.

@item PROGRAM
Name of the program used.  By default, it is set to the name of the
program launched, with a trailing @samp{.pl} removed.

@pindex texi-elements-by-size
@cindex Longest nodes, finding
@cindex Sorting nodes by size
@item SORT_ELEMENT_COUNT
If set, the name of a file to which a list of elements (nodes or
sections, depending on the output format) is dumped, sorted by the
number of lines they contain after removal of @@-commands; default
unset.  This is used by the program @code{texi-elements-by-size} in
the @file{util/} directory of the Texinfo source distribution
(@pxref{texi-elements-by-size}).

@item SORT_ELEMENT_COUNT_WORDS
When dumping the elements-by-size file (see preceding item), use word
counts instead of line counts; default false.

@item TEST
If set to a positive integer, some variables which are normally dynamically
generated anew for each run (date, program name, version) are set to
fixed and given values.  Some file names may also have the directory part
removed.  Also code that gives more reproducible output may be selected.
This is useful to compare the output to a reference file, as is done for the
tests.  Features not selected in the default case but interesting for tests are
also enabled.  For example, code related to memory release and checks on
released memory.  If the value is higher, more checks are enabled, which may
require additional Perl modules installation.  The default is undef.

@item TEXINFO_OUTPUT_FORMAT
The generated output format.  Set from command line with options such as
@option{--html}, as the @env{TEXINFO_OUTPUT_FORMAT} environment variable
value (@pxref{@command{texi2any} Environment Variables}) or as a customization
option.  @xref{Output Format Selection}

@item TREE_TRANSFORMATIONS
The associated value is a comma separated list of transformations that
can be applied to the Texinfo tree prior to outputting the result.  If
more than one is specified, the ordering is irrelevant; each is always
applied at the necessary point during processing.

By default, the tree transformations @samp{move_index_entries_after_items}
and @samp{relate_index_entries_to_table_entries} are executed
for HTML and DocBook output.
Here's an example of updating the master menu in a document:

@example
texi2any \
  -c TREE_TRANSFORMATIONS=regenerate_master_menu \
  -c TEXINFO_OUTPUT_FORMAT=plaintexinfo \
  mydoc.texi \
  -o /tmp/out
@end example

@noindent (Caveat: Since @samp{plaintexinfo} output expands
Texinfo macros and conditionals, it's necessary to remove any such
differences before installing the updates in the original document.
This may be remedied in a future release.)

The following transformations are currently supported (many are used
in the @code{pod2texi} utility distributed with Texinfo;
@pxref{Invoking @command{pod2texi}}):

@ftable @samp
@item complete_tree_nodes_menus
Add menu entries or whole menus for nodes associated with sections of
any level, based on the sectioning tree.

@item complete_tree_nodes_missing_menu
Add whole menus for nodes associated with sections without menu.  The
menus are based on the sectioning tree.

@item fill_gaps_in_sectioning
Adds empty @code{@@unnumbered...} sections in a tree to fill gaps in
sectioning.  For example, an @code{@@unnumberedsec} will be inserted
if a @code{@@chapter} is followed by a @code{@@subsection}.

@item insert_nodes_for_sectioning_commands
Insert nodes for sectioning commands lacking a corresponding node.

@item move_index_entries_after_items
In @code{@@enumerate} and @code{@@itemize}, move index entries
appearing just before an @code{@@item} to just after the
@code{@@item}.  Comment lines between index entries are moved too.  As
mentioned, this is always done for HTML and DocBook output.

@item regenerate_master_menu
Update the Top node master menu, either replacing the (first)
@code{@@detailmenu} in the Top node menu, or creating it at the end of
the Top node menu.

@item relate_index_entries_to_table_entries
In @code{@@table}, @code{@@vtable} and @code{@@ftable},
reassociate the index entry information from an index @@-command
appearing right after an @code{@@item} line with the first element of
the @code{@@item}.  Remove the index @@-command from the tree.

@end ftable

@item USE_SETFILENAME_EXTENSION
Default is on for Info, off for other output.  If set, use exactly
what @code{@@setfilename} gives for the output file name, including
the extension.  You should not need to explicitly set this variable.

@item USE_UNICODE_COLLATION
By default, @command{texi2any} sorts document indices according to
the @dfn{Unicode Collation Algorithm} (defined in
@uref{http://www.unicode.org/reports/tr10/, Unicode Technical Standard #10}),
which performs a @dfn{multi-level} ordering of strings.

Set this variable to @samp{0} to use a simpler, faster sorting algorithm.

You may find this useful for speeding up @command{texi2any} if you don't care
about having the indices sorted correctly, especially when working on
the draft of a manual.

@end vtable


@node Info and Plaintext Customization Variables
@subsection Info and Plaintext Customization Variables

This table gives the customization variables which apply to Info
and Plaintext formats only.

@vtable @code
@item ASCII_DASHES_AND_QUOTES
For Info output, when set, use plain ASCII characters to represent
quotation marks, hyphens and dashes when these are given in the Texinfo
source as @samp{-}, @samp{--}, @samp{---}, @samp{`}, @samp{``},
@samp{'}, and @samp{''}, rather than UTF-8 directional quotation marks,
en dashes, vel sim.  On by default.

@item ASCII_GLYPH
For Info output, use ASCII output for glyph commands such as the copyright
sign (@command{@@copyright@{@}}, becoming @samp{(C)}),
and the bullet symbol (@command{@@bullet@{@}}, becoming @samp{*}), rather
than other Unicode sequences.  Off by default.

@item ASCII_PUNCTUATION
Avoid any unnecessary or gratuitous non-ASCII, UTF-8 sequences in the
output.  Implies both @code{ASCII_DASHES_AND_QUOTES} and @code{ASCII_GLYPH}
and additionally affects the output of commands such as @code{@@samp} which
output quotation marks.

@item AUTO_MENU_DESCRIPTION_ALIGN_COLUMN
For Info output, column at which to start a menu entry description
provided by @code{@@nodedescription} or @code{@@nodedescriptionblock}.
Undefined by default, in which case 45% of the fill column value is used
(@pxref{Invoking @command{texi2any}}).

@item AUTO_MENU_MAX_WIDTH
Maximum number of columns in a menu entry line in Info when adding a
description from @code{@@nodedescription} or @code{@@nodedescriptionblock}.
Undefined by default, in which case 10% more than the fill column value
is used (@pxref{Invoking @command{texi2any}}).

@item CLOSE_DOUBLE_QUOTE_SYMBOL
When a closing double quote is needed, for @samp{@@dfn} in Info, use this
character.  The default for Info is set the same as for
@code{OPEN_DOUBLE_QUOTE_SYMBOL}, except that the Unicode code is a closing
double quote (see below).

@item INDEX_SPECIAL_CHARS_WARNING
If set, warn about @samp{:} in index entry, as not all Info readers may
be able to process these.  For Info and plaintext only.  Default false,
because parsing problems there don't prevent navigation; readers can still
relatively easily find their way to the node in question.

@item INFO_MATH_IMAGES
(Experimental.)
If set, convert the contents of @code{@@math} and @code{@@displaymath}
into images, and reference these in the produced Info file.  This variable
requires a working @TeX{} installation, the @samp{preview} package
of @LaTeX{}, as well as the @command{dvipng} program.  It may be suitable
for math-heavy documents that are unlikely to be viewed in a text terminal.

This feature is marked as experimental as it would require extra support
in Info-viewing programs (currently, only the Info mode of Emacs) to
view the images correctly.  The images should be visible with existing
versions of Emacs, but they may be the wrong size or appear misaligned
with surrounding text.  It is possible that we will change the output
for this option given further feedback.  @xref{Info Format Image} for
more details about how images are currently output with this option.

@item INFO_SPECIAL_CHARS_QUOTE
If set, whenever there are problematic characters for Info output in
places such as node names or menu items, surround the part of the
construct where they appear with quoting characters, as described in
@ref{Info Format Specification}.  Default is set for Info and unset
for plaintext.  @xref{Node Line Requirements}.

@item INFO_SPECIAL_CHARS_WARNING
If set, warn about problematic constructs for Info output (such as the
string @samp{::}) in node names, menu items, and cross-references.
If not defined, set unless @code{INFO_SPECIAL_CHARS_QUOTE} is set.
Default is set for Info and not defined for plaintext. Similar warnings in
index entries are covered by @code{INDEX_SPECIAL_CHARS_WARNING}.

@item OPEN_DOUBLE_QUOTE_SYMBOL
When an opening double quote is needed, for @samp{@@dfn} output in Info, use
the specified character.  If @option{--disable-encoding} is set or the document
encoding is not UTF-8, @samp{"} is used.  Otherwise, the Info output uses a
Unicode left double quote.

@end vtable


@node @LaTeX{} Customization Variables
@subsection @LaTeX{} Customization Variables

@cartouche
@quotation warning
@LaTeX{} output customization is experimental.  Nothing is decided,
everything can change, and we would welcome any feedback.
@end quotation
@end cartouche

This table gives the customization variables which apply to @LaTeX{} output
only.

@vtable @code
@item CLASS_BEGIN_USEPACKAGE
If set, the corresponding text will replace the @LaTeX{} @code{\documentclass},
package imports that are always output and are output right after
@code{\documentclass}, and package imports that depend on the document encoding
setting the input and font encoding (@code{inputenc} and @code{fontenc}).

The text replaced is along:
@example LaTeX
\documentclass@{book@}
\usepackage@{amsfonts@}
\usepackage@{amsmath@}
\usepackage[gen]@{eurosym@}
\usepackage@{textcomp@}
\usepackage@{graphicx@}
\usepackage@{etoolbox@}
\usepackage@{titleps@}
\usepackage[utf8]@{inputenc@}
\usepackage[T1]@{fontenc@}
@end example

@item END_USEPACKAGE
If set, the corresponding text will replace the package imports that depend
on the Texinfo commands used, and the last packages imports that are always
output and output after all the other packages imports.  The last package
imports corresponds to @samp{\usepackage[hidelinks]@{hyperref@}}.

Here is an example of the corresponding text for a document with indices,
@code{@@need}, @code{@@multitable}, definition commands, @code{@@cartouche},
lists, and @code{@@float}:
@example LaTeX
\usepackage@{imakeidx@}
\usepackage@{needspace@}
\usepackage@{array@}
\usepackage@{embrac@}
\usepackage@{expl3@}
\usepackage@{tabularx@}
\usepackage[framemethod=tikz]@{mdframed@}
\usepackage@{enumitem@}
\usepackage@{float@}
\usepackage[hidelinks]@{hyperref@}
@end example

@item LATEX_FLOATS_FILE_EXTENSION
Set new floats definition file extension for @LaTeX{} output.
Default @samp{tfl}.

@end vtable


@node Other Formats Customization Variables
@subsection Other Formats Customization Variables

This table gives the customization which apply to specific formats only,
for formats without separate customization variables description section.

@vtable @code
@item TEXI2DVI
Name of the command used to produce PostScript, PDF, and DVI; default
@samp{texi2dvi}.  @xref{@command{texi2any} Printed Output}.

@item TEXTCONTENT_COMMENT
For stripped text content output (i.e., when
@code{TEXINFO_OUTPUT_FORMAT} is set to @code{textcontent}).  If set,
also output comments.  Default false.

@end vtable


@node Customization Variables for Multiple Formats
@subsection Customization Variables for Multiple Formats

@anchor{Other Customization Variables} @c old name

This table gives the customization which apply to multiple formats.

@vtable @code
@item CLOSE_QUOTE_SYMBOL
When a closing quote is needed, e.g.@: for @code{@@samp} output, use
this character; default @code{&#8217;} in DocBook.
Undefined in the default case in HTML and set to @code{&rsquo;}
if @code{USE_NUMERIC_ENTITY} is not set, to @code{&#8217;} if set, and
to a quote character if @code{OUTPUT_CHARACTERS} is set and the output
encoding includes that character.

The default for Info is set the same as for @code{OPEN_QUOTE_SYMBOL},
except that the Unicode code is a closing quote (see below).

@vindex SystemLiteral
@item DOCTYPE
For DocBook, HTML@.  Specifies the @code{SystemLiteral}, the
entity's system identifier.  This is a URI which may be used to
retrieve the entity, and identifies the canonical DTD for the
document.  The default value is different for each of HTML and DocBook.

@item EXTENSION
The extension added to the output file name.  The default is different
for each output format.

@item NO_TOP_NODE_OUTPUT
@anchor{@code{NO_TOP_NODE_OUTPUT}}
If set do not output the Top node content.  The Top node is still
parsed, but the content is discarded.  Not set in the default case
for HTML@.  Set in the default case for EPUB@.  If @code{SHOW_TITLE}
is @samp{undef}, setting @code{NO_TOP_NODE_OUTPUT} also sets
@code{SHOW_TITLE} for HTML.

Setting @code{NO_TOP_NODE_OUTPUT}, which removes the Top node and adds
a title page corresponds more to the formatting of a book.  Setting
@code{NO_TOP_NODE_OUTPUT} to false, with @code{SHOW_TITLE} remaining
@samp{undef}, and false, corresponds more to a document setup for browsing,
with a direct access to the information at the Top node.

For DocBook, @code{NO_TOP_NODE_OUTPUT} is set to true.  Setting
@code{NO_TOP_NODE_OUTPUT} to false causes the Top node content to be
output.  It is not recommended to output the Top node in DocBook as
the title and copying texts are always output.  This option
is kept for DocBook for compatibility, as before 2022 the Top node was output
in DocBook.  It could be removed in the future.

@item OPEN_QUOTE_SYMBOL
When an opening quote is needed, e.g., for @samp{@@samp} output, use
the specified character; default @code{&#8216;} for DocBook.
Undefined in the default case in HTML and set to @code{&lsquo;}
if @code{USE_NUMERIC_ENTITY} is not set, to @code{&#8216;} if set, and
to a quote character if @code{OUTPUT_CHARACTERS} is set and the output
encoding includes that character.

For Info, the default depends on the enabled document encoding.  If
@option{--disable-encoding} is set or the document encoding is not UTF-8,
@samp{'} is used.  This character usually appears
as an undirected single quote on modern systems.  Otherwise, the Info
output uses a Unicode left quote.

@item OUTPUT_CHARACTERS
If not set, the default, output accented and special characters in HTML
and DocBook using XML entities, and in @LaTeX{} using macros.  If set, output
accented characters in HTML, DocBook and @LaTeX{} output and special
characters in HTML and @LaTeX{} output based on the document encoding.
@xref{@code{@@documentencoding}}, and @ref{Inserting Accents}.

@anchor{TOP_NODE_UP}
@item TOP_NODE_UP
Up node for the Top node; default @samp{(dir)}.  This node name is
supposed to be already formatted for the output format.  In HTML
can be used in attribute, so should not contain any element.  Used for
HTML output only if @code{TOP_NODE_UP_URL} is set to override the URL@:,
see @code{TOP_NODE_UP_URL} in @ref{HTML Customization Variables List}.
@xref{File Names and Links Customization for HTML}.

@item USE_NODES
The main unit of output documents is an @dfn{output unit}.  Usually a node is
associated with a following sectioning command, while a sectioning command is
associated with a previous node; they both together make up the output unit.

For Plaintext and HTML@.  Preferentially use nodes to decide where output units
are separated if @code{USE_NODES} is set.  If set to false, preferentially use
sectioning to decide where output units are separated.  The default is true.

@item USE_NUMERIC_ENTITY
For HTML and DocBook@.  If set, use numeric entities instead of named
entities.  By default, set to true for DocBook output.

@end vtable


@node Internationalization of Document Strings
@nodedescription Translating program-inserted text.
@section Internationalization of Document Strings

@cindex I18n, of document strings
@cindex Internationalization of document strings
@cindex Document strings, internationalization of
@cindex Output document strings, internationalization of
@cindex Translating strings in output documents

@vindex documentlanguage @r{customization variable}
@vindex documentscript @r{customization variable}
@command{texi2any} writes fixed strings into the output document at
various places: cross-references, page footers, the help page,
alternate text for images, and so on.  The string chosen depends on
the value of the @code{documentlanguage}, @code{documentscript}
and @code{@@documentlanguagevariant}
at the time of the string
being output (@pxref{Setting the language}, for the Texinfo
command interface).

@vindex texinfo_document @r{Gettext domain}
@cindex Perl format strings for translation
The Gettext framework with the @samp{texinfo_document} domain
is used for those strings (@pxref{Top,,, gettext, Gettext}).
Translated strings are written as Texinfo, and may include
@@-commands.  In translated strings, the varying parts of the string
are denoted by @samp{@{arg_name@}}, but not by @code{%s} and the like.
(This convention is common for @code{gettext} in Perl and is fully
supported in GNU Gettext; @pxref{perl-format,, Perl Format Strings,
gettext, GNU Gettext}.)  For example, in the following, @samp{@{section@}}
will be replaced by the section name:

@example
see @{section@}
@end example

@c Ignore, there is no need to justify this choice
@ignore
These Perl-style brace format strings are used because the order of arguments
is unpredictable, since @@-command expansion may lead to different
orders depending on the output format.
@end ignore

The expansion of a translation string is done like this:

@enumerate
@item First, the string is translated.  The locale is based on the
@var{documentlanguage}, with a @samp{@@modifier} appended based on
@var{documentscript} or @var{documentlanguagevariant}, if set.

If the locale has the form @samp{ll_CC}, @samp{ll@@modifier} or
@samp{ll_CC@@modifier}, that is tried first, and then just @samp{ll}.

@item Next, in most cases, the string is expanded as Texinfo, and converted.
The arguments are substituted; for example, @samp{@{arg_name@}} is replaced by
the corresponding actual argument.

It is also possible for the string and the argument to be already converted.
In that case, the arguments are simply substituted.  Similarly,
@samp{@{arg_name@}} is replaced by the corresponding actual argument.

@end enumerate

In the following example, @samp{@{date@}}, @samp{@{program_homepage@}}
and @samp{@{program@}} are the arguments of the string.  Since they
are used in @code{@@uref}, their order is not predictable.
@samp{@{date@}}, @samp{@{program_homepage@}} and @samp{@{program@}} are
substituted after the expansion:

@example
Generated on @@emph@{@{date@}@} using
@@uref@{@{program_homepage@}, @@emph@{@{program@}@}@}.
@end example

This approach is admittedly a bit complicated.  Its usefulness is that it
supports specifying the formatting of the translated string independently
of the output format.

For example, the @samp{@@pxref} translation string can be like this:

@example
see @{node_file_href@} section `@{section@}' in @@cite@{@{book@}@}
@end example

@noindent
which allows for specifying a string independently of the output
format, while nevertheless with rich formatting it may be translated
appropriately in many languages.

@c TODO Seems like an implementation detail.  Remove?
@pindex libintl-perl @r{Gettext implementation}
If Perl is used for strings translation in @command{texi2any}, the
@code{libintl-perl} package is used as the @code{gettext} implementation; more
specifically, the pure Perl implementation is used, so Texinfo can support
consistent behavior across all platforms and installations, which would not
otherwise be possible.  @code{libintl-perl} is included in the Texinfo
distribution and always installed, to ensure that it is available if needed.
It is also possible to use the system @code{libintl-perl} (the choice can be
made at build-time).


@node Invoking @command{pod2texi}
@nodedescription Translating Perl Pod to Texinfo.
@section Invoking @command{pod2texi}: Convert Pod to Texinfo

@pindex pod2texi
@cindex Invoking @command{pod2texi}
@cindex Pod, converting to Texinfo
@cindex Perl Pod, converting to Texinfo

The @command{pod2texi} program converts Perl Pod documentation file(s)
to Texinfo.  There are two basic modes of operation: generating a
standalone Texinfo document from each input Pod, or (if @code{--base-level=1}
or higher is given) generating Texinfo subfiles suitable for use with
@code{@@include}.

@c Although ordinarily this documentation in the Texinfo manual would be
@c the best place to look, in this case we have documented all the
@c options and examples in the @command{pod2texi} program itself, since it
@c may be useful outside of the rest of Texinfo.  Thus, please see the
@c output of @code{pod2texi --help}, the version on the web at
@c @url{https://www.gnu.org/software/texinfo/manual/pod2texi.html}, etc.

The @command{pod2texi} program may be useful outside of the rest of Texinfo;
thus, the invocation of @command{pod2texi} is documented in the Pod language
using the man page format to follow the convention used in Perl standalone
programs, with a version on the web
@url{https://www.gnu.org/software/texinfo/manual/pod2texi.html} and a version
included below.  The version included in the manual is also an example of
@command{pod2texi} use, as it is converted from Pod using @command{pod2texi}.

@c there are issue with the perldoc-all generated files, as the perl documentation
@c does not follows the Pod specification, there are anchors added
@c using the first word in addition to the regular anchors.
@c For an example of using @command{pod2texi} to make Texinfo out of the
@c Perl documentation itself, see @file{contrib/perldoc-all}} in the Texinfo
@c source distribution.


@node pod2texi manual page
@nodedescription @command{pod2texi} invocation in a manual page format.
@include pod2texi.texi


@node @command{texi2html}
@nodedescription An ancestor of @command{texi2any}.
@section @command{texi2html}: Ancestor of @command{texi2any}

@pindex texi2html

@cindex Cons, Lionel
Conceptually, the @command{texi2html} program is the parent of today's
@command{texi2any} program.  @command{texi2html} was developed
independently, originally by Lionel Cons in 1998; at the time,
@command{makeinfo} could not generate HTML@.  Many other people
contributed to @command{texi2html} over the years.

The present @command{texi2any} uses little of the actual code of
@command{texi2html}, and has quite a different basic approach to the
implementation (namely, parsing the Texinfo document into a tree), but
still, there is a family resemblance.

By design, @command{texi2any} supports nearly all the features of
@command{texi2html} in some way.  However, we did not attempt to
maintain strict compatibility, so no @command{texi2html} executable is
installed by the Texinfo package.  An approximation can be run with an
invocation like this:

@example
texi2any --set-customization-variable TEXI2HTML=1 ...
@end example

@noindent but, to emphasize, this is @emph{not} a drop-in replacement
for the previous @command{texi2html}.  Here are the biggest differences:

@itemize @bullet
@item Most blatantly, the command line options of @command{texi2html}
are now customization variables, for the most part.  A table of
approximate equivalents is given below.

@item The program-level customization API is very different in
@command{texi2any}.

@item Indices cannot be split.

@end itemize

We do not intend to reimplement these
differences.  Therefore, the route forward for authors is alter
manuals and build processes as necessary to use the new features and
methods of @command{texi2any}.  The @command{texi2html} maintainers
(one of whom is the principal author of @command{texi2any}) do not
intend to make further releases.

@cindex Options of @command{texi2html}
@cindex Command-line options of @command{texi2html}
Here is the table showing @command{texi2html} options and
corresponding @command{texi2any} customization variables.
@c (@pxref{texi2any Output Customization,, @command{texi2any} Output
@c Customization}).

@multitable {@option{--frameset-doctype}} {@code{HTML_MATH} set to @samp{l2h}}

@item @option{--toc-links}            @tab @code{TOC_LINKS}
@item @option{--short-ext}            @tab @code{EXTENSION} set to @samp{htm}
@item @option{--prefix}               @tab @code{PREFIX}
@item @option{--def-table}            @tab @code{DEF_TABLE}
@item @option{--html-xref-prefix}     @tab @code{EXTERNAL_DIR}
@item @option{--l2h}                  @tab @code{HTML_MATH} set to @samp{l2h}
@item @option{--l2h-l2h}              @tab @code{L2H_L2H}
@item @option{--l2h-skip}             @tab @code{L2H_SKIP}
@item @option{--l2h-tmp}              @tab @code{L2H_TMP}
@item @option{--l2h-file}             @tab @code{L2H_FILE}
@item @option{--l2h-clean}            @tab @code{L2H_CLEAN}
@item @option{--use-nodes}            @tab @code{USE_NODES}
@item @option{--monolithic}           @tab @code{MONOLITHIC}
@item @option{--top-file}             @tab @code{TOP_FILE}
@item @option{--frames}               @tab no equivalent
@item @option{--menu}                 @tab @code{FORMAT_MENU}
@item @option{--debug}                @tab @code{DEBUG}
@item @option{--doctype}              @tab @code{DOCTYPE}
@item @option{--frameset-doctype}     @tab no equivalent
@item @option{--test}                 @tab @code{TEST}
@end multitable

@cindex @file{texi2oldapi.texi}, for @command{texi2html}
Finally, any @command{texi2html} users seeking more detailed information can
check the first part of the archived file @file{doc/texi2oldapi.texi} in the
Texinfo source repository.


@node Creating and Installing Info Files
@nodedescription Details on Info output.
@chapter Creating and Installing Info Files

@anchor{Creating an Info File}@c removed, merged to this node and Emacs Info mode

This chapter gives some information on the Info output and describes how to
install Info files.  For the creation of Info files with @command{texi2any}, see
@ref{Generic Translator @command{texi2any}}, and with Emacs, @ref{Info
Formatting}.  @xref{Info Files}, for general information about the file format.
@xref{Info Format Specification}, for a detailed technical specification of the
Info format.


@node Installing an Info File
@section Installing an Info File
@cindex Installing an Info file
@cindex Info files @subentry installation
@cindex @file{dir} directory for Info installation

Info files are usually kept in the @file{info} directory.  You can
read Info files using the standalone Info program or the Info reader
built into Emacs.  (@xref{Top,,, info, Info}, for an introduction to
Info.)


@node Directory File
@nodedescription The top-level menu for all Info files.
@subsection The Directory File @file{dir}

For Info to work, the @file{info} directory must contain a file that
serves as a top-level directory for the Info system.  By convention,
this file is called @file{dir}.  (You can find the location of this file
within Emacs by typing @kbd{C-h i} to enter Info and then typing
@kbd{C-x C-f} to see the location of the @file{info} directory.)

The @file{dir} file is itself an Info file.  It contains the top-level
menu for all the Info files in the system.  The menu looks like
this:

@example
@group
* Menu:
* Info:    (info).     Documentation browsing system.
* Emacs:   (emacs).    The extensible, self-documenting
                      text editor.
* Texinfo: (texinfo).  With one source file, make
                      either a printed manual using
                      @@TeX@{@} or an Info file.
@dots{}
@end group
@end example

Each of these menu entries points to the `Top' node of the Info file
that is named in parentheses.  (The menu entry does not need to
specify the `Top' node, since Info goes to the `Top' node if no node
name is mentioned.  @xref{Other Info Files, , Nodes in Other Info
Files}.)

Thus, the @samp{Info} entry points to the `Top' node of the
@file{info} file and the @samp{Emacs} entry points to the `Top' node
of the @file{emacs} file.

In each of the Info files, the `Up' pointer of the `Top' node refers
back to the @code{dir} file.  For example, the line for the `Top'
node of the Emacs manual looks like this in Info:

@example
File: emacs  Node: Top, Up: (DIR), Next: Distrib
@end example

@noindent
In this case, the @file{dir} file name is written in uppercase
letters---it can be written in either upper- or lowercase.  This is not
true in general, it is a special case for @file{dir}.

See the @file{util/dir-example} file in the Texinfo distribution for
a large sample @code{dir} file.


@node New Info File
@nodedescription Listing a new Info file.
@subsection Listing a New Info File
@cindex Adding a new Info file
@cindex Listing a new Info file
@cindex New Info file, listing it in @file{dir} file
@cindex Info files @subentry listing a new
@cindex @file{dir} file listing

To add a new Info file to your system, you must write a menu entry to
add to the menu in the @file{dir} file in the @file{info} directory.
For example, if you were adding documentation for GDB, you would write
the following new entry:

@example
* GDB: (gdb).           The source-level C debugger.
@end example

@noindent
The first part of the menu entry is the menu entry name, followed by a
colon.  The second part is the name of the Info file, in parentheses,
followed by a period.  The third part is the description.

The name of an Info file often has a @file{.info} extension.  Thus, the
Info file for GDB might be called either @file{gdb} or @file{gdb.info}.
The Info reader programs automatically try the file name both with and
without @file{.info}@footnote{On MS-DOS/MS-Windows systems, Info will
try the @file{.inf} extension as well.}; so it is better to avoid
clutter and not to write @samp{.info} explicitly in the menu entry.  For
example, the GDB menu entry should use just @samp{gdb} for the file
name, not @samp{gdb.info}.


@node Other Info Directories
@nodedescription How to specify Info files that are located in other directories.
@subsection Info Files in Other Directories
@cindex Installing Info in another directory
@cindex Info installed in another directory
@cindex Another Info directory
@cindex @file{dir} files and Info directories

If an Info file is not in the @file{info} directory, there are three
ways to specify its location:

@enumerate
@item
Write the file name in the @file{dir} file as the second part of the menu.

@item
Specify the Info directory name in the @code{INFOPATH} environment
variable in your @file{.profile} or @file{.cshrc} initialization file.
(Only you and others who set this environment variable will be able to
find Info files whose location is specified this way.)

@item
If you are using Emacs, list the name of the file in a second @file{dir}
file, in its directory; and then add the name of that directory to the
@code{Info-directory-list} variable in your personal or site
initialization file.

This variable tells Emacs where to look for @file{dir} files (the files
must be named @file{dir}).  Emacs merges the files named @file{dir} from
each of the listed directories.  (In Emacs version 18, you can set the
@code{Info-directory} variable to the name of only one
directory.)
@end enumerate

For example, to reach a test file in the @file{/home/bob/info}
directory, you could add an entry like this to the menu in the
standard @file{dir} file:

@example
* Test: (/home/bob/info/info-test).  Bob's own test file.
@end example

@noindent
In this case, the absolute file name of the @file{info-test} file is
written as the second part of the menu entry.

@vindex INFOPATH
@cindex Environment variable @code{INFOPATH}
If you don't want to edit the system @file{dir} file, you can tell
Info where to look by setting the @code{INFOPATH} environment variable
in your shell startup file.  This works with both the Emacs and
standalone Info readers.

Emacs uses the @code{INFOPATH} environment variable to initialize the value of
Emacs's own @code{Info-directory-list} variable.  The standalone Info reader
merges any files named @file{dir} in any directory listed in the
@env{INFOPATH} variable into a single menu presented to you in the node
called @samp{(dir)Top}.

@cindex Colon, last in @env{INFOPATH}
However you set @env{INFOPATH}, if its last character is a colon (on
MS-DOS/MS-Windows systems, use a semicolon instead), this is replaced
by the default (compiled-in) path.  This gives you a way to augment
the default path with new directories without having to list all the
standard places.  For example (using @code{sh} syntax):

@example
INFOPATH=/home/bob/info:
export INFOPATH
@end example

@noindent
will search @file{/home/bob/info} first, then the standard directories.
Leading or doubled colons are not treated specially.

@cindex @file{dir} file, creating your own
When you create your own @file{dir} file for use with
@code{Info-directory-list} or @env{INFOPATH}, it's easiest to start by
copying an existing @file{dir} file and replace all the text after the
@samp{* Menu:} with your desired entries.  That way, the punctuation
and special @kbd{CTRL-_} characters that Info needs will be present.

As one final alternative, which works only with Emacs Info, you can
change the @code{Info-directory-list} variable.  For example:

@example
(add-hook 'Info-mode-hook '(lambda ()
	     (add-to-list 'Info-directory-list
			  (expand-file-name "~/info"))))
@end example


@node Installing Dir Entries
@nodedescription How to specify what menu entry to add to the Info directory.
@subsection Installing Info Directory Files

When you install an Info file onto your system, you can use the program
@code{install-info} to update the Info directory file @file{dir}.
Normally the makefile for the package runs @code{install-info}, just
after copying the Info file into its proper installed location.

@findex direntry
In order for the Info file to work with @code{install-info}, you include
the commands @code{@@dircategory} and
@code{@@direntry}@dots{}@code{@@end direntry} in the Texinfo source
file.

@cindex Invoking nodes, including in dir file
Use @code{@@dircategory} to specify a category
for the manual, which determines which part of the Info directory to
put it in. (@xref{Directory Category}.)
Use @code{@@direntry} to specify the menu entry, or entries, to add
to the Info directory file.  Some manuals (such as the manual you are
reading now, or that of GNU Coreutils; @pxref{Top,,, coreutils, GNU Coreutils})
will have several entries.
It is typical to have one dir entry for each program that a package
installs, usually to the program's `Invoking' node. This lets users
easily find the documentation for the different programs they can run.
@c as with the traditional @command{man} system.
Likewise, a manual for a C library may install a dir entry for each
function it provides.


@c NB this is referenced from node "Directory Category"
Here is how these commands are used in this manual:

@example
@@dircategory Texinfo documentation system
@@direntry
* Texinfo: (texinfo).           The GNU documentation format.
* install-info: (texinfo)Invoking install-info. @dots{}
@dots{}
@@end direntry
@end example

Here's what this produces in the Info file:

@example
INFO-DIR-SECTION Texinfo documentation system
START-INFO-DIR-ENTRY
* Texinfo: (texinfo).           The GNU documentation format.
* install-info: (texinfo)Invoking install-info. @dots{}
@dots{}
END-INFO-DIR-ENTRY
@end example

@noindent
The @code{install-info} program sees these lines in the Info file, and
that is how it knows what to do.

Always use the @code{@@direntry} and @code{@@dircategory} commands near
the beginning of the Texinfo input, before the first @code{@@node}
command.  If you use them later on in the input, @code{install-info}
will not notice them.

@code{install-info} will automatically reformat the description of the
menu entries it is adding.  As a matter of convention, the description
of the main entry (above, @samp{The GNU documentation format}) should
start at column 32, starting at zero (as in
@code{what-cursor-position} in Emacs).  This will make it align with
most others.  Description for individual utilities best start in
column 48, where possible.  For more information about formatting see
the @samp{--calign}, @samp{--align}, and @samp{--max-width} options in
@ref{Invoking @command{install-info}}.

If you use @code{@@dircategory} more than once in the Texinfo source,
each usage specifies the `current' category; any subsequent
@code{@@direntry} commands will add to that category.


@node Invoking @command{install-info}
@nodedescription @code{install-info} options.
@subsection Invoking @command{install-info}

@pindex install-info

@code{install-info} inserts menu entries from an Info file into the
top-level @file{dir} file in the Info system (see the previous sections
for an explanation of how the @file{dir} file works).  @code{install-info}
also removes menu entries from the @file{dir} file.  It's most often
run as part of software installation, or when constructing a @file{dir} file
for all manuals on a system.  Synopsis:

@example
install-info [@var{option}@dots{}] [@var{info-file} [@var{dir-file}]]
@end example

If @var{info-file} or @var{dir-file} are not specified, the options
(described below) that define them must be.  There are no compile-time
defaults, and standard input is never used.  @code{install-info} can
read only one Info file and write only one @file{dir} file per invocation.

@cindex @file{dir}, created by @code{install-info}
If @var{dir-file} (however specified) does not exist,
@code{install-info} creates it if possible (with no entries).

@cindex Compressed dir files, reading
@cindex XZ-compressed dir files, reading
@cindex Bzipped dir files, reading
@cindex Lzip-compressed dir files, reading
@cindex LZMA-compressed dir files, reading
@cindex Dir files, compressed
If any input file is compressed with @code{gzip} (@pxref{Top,,, gzip,
Gzip}), @code{install-info} automatically uncompresses it for reading.
And if @var{dir-file} is compressed, @code{install-info} also
automatically leaves it compressed after writing any changes.  If
@var{dir-file} itself does not exist, @code{install-info} tries to
open @file{@var{dir-file}.gz}, @file{@var{dir-file}.xz},
@file{@var{dir-file}.bz2}, @file{@var{dir-file}.lz}, and
@file{@var{dir-file}.lzma}, in that order.

Options:

@table @code
@item --add-once
@opindex --add-once@r{, for @command{install-info}}
Specifies that the entry or entries will only be put into a single section.

@item --align=@var{column}
@opindex --align=@var{column}@r{, for @command{install-info}}
Specifies the column that the second and subsequent lines of menu entry's
description will be formatted to begin at.  The default for this option is
@samp{35}.  It is used in conjunction with the @samp{--max-width} option.
@var{column} starts counting at 1.

@item --append-new-sections
@opindex --append-new-sections@r{, for @command{install-info}}
Instead of alphabetizing new sections, place them at the end of the DIR file.

@item --calign=@var{column}
@opindex --calign=@var{column}@r{, for @command{install-info}}
Specifies the column that the first line of menu entry's description will
be formatted to begin at.  The default for this option is @samp{33}.  It is
used in conjunction with the @samp{--max-width} option.
When the name of the menu entry exceeds this column, entry's description
will start on the following line.
@var{column} starts counting at 1.

@item --debug
@opindex --debug@r{, for @command{install-info}}
Report what is being done.

@item --delete
@opindex --delete@r{, for @command{install-info}}
Delete the entries in @var{info-file} from @var{dir-file}.  The file
name in the entry in @var{dir-file} must be @var{info-file} (except for
an optional @samp{.info} in either one).  Don't insert any new entries.
Any empty sections that result from the removal are also removed.

@item --description=@var{text}
@opindex --description=@var{text}@r{, for @command{install-info}}
Specify the explanatory portion of the menu entry.  If you don't specify
a description (either via @samp{--entry}, @samp{--item} or this option),
the description is taken from the Info file itself.

@item --dir-file=@var{name}
@opindex --dir-file=@var{name}@r{, for @command{install-info}}
Specify file name of the Info directory file.  This is equivalent to
using the @var{dir-file} argument.

@item --dry-run
@opindex --dry-run@r{, for @command{install-info}}
Same as @samp{--test}.

@item --entry=@var{text}
@opindex --entry=@var{text}@r{, for @command{install-info}}
Insert @var{text} as an Info directory entry; @var{text} should have the
form of an Info menu item line plus zero or more extra lines starting
with whitespace.  If you specify more than one entry, they are all
added.  If you don't specify any entries, they are determined from
information in the Info file itself.

@item --help
@opindex --help@r{, for @command{texindex}}
Display a usage message with basic usage and all available options,
then exit successfully.

@item --info-file=@var{file}
@opindex --info-file=@var{file}@r{, for @command{install-info}}
Specify Info file to install in the directory.  This is
equivalent to using the @var{info-file} argument.

@item --info-dir=@var{dir}
@opindex --info-dir=@var{dir}@r{, for @command{install-info}}
Specify the directory where the directory file @file{dir} resides.
Equivalent to @samp{--dir-file=@var{dir}/dir}.

@item --infodir=@var{dir}
@opindex --infodir=@var{dir}@r{, for @command{install-info}}
Same as @samp{--info-dir}.

@item --item=@var{text}
@opindex --item=@var{text}@r{, for @command{install-info}}
Same as @samp{--entry=@var{text}}.  An Info directory entry is actually
a menu item.

@item --keep-old
@opindex --keep-old@r{, for @command{install-info}}
Do not replace pre-existing menu entries.  When @samp{--remove} is specified,
this option means that empty sections are not removed.

@item --max-width=@var{column}
@opindex --max-width=@var{column}@r{, for @command{install-info}}
Specifies the column that the menu entry's description will be word-wrapped
at.  @var{column} starts counting at 1.

@item --maxwidth=@var{column}
@opindex --maxwidth=@var{column}@r{, for @command{install-info}}
Same as @samp{--max-width}.

@item --menuentry=@var{text}
@opindex --menuentry=@var{text}@r{, for @command{install-info}}
Same as @samp{--name}.

@item --name=@var{text}
@opindex --name=@var{text}@r{, for @command{install-info}}
Specify the name portion of the menu entry.  If the @var{text} does
not start with an asterisk @samp{*}, it is presumed to be the text
after the @samp{*} and before the parentheses that specify the Info
file.  Otherwise @var{text} is taken verbatim, and is taken as
defining the text up to and including the first period (a space is
appended if necessary).  If you don't specify the name (either via
@samp{--entry}, @samp{--item} or this option), it is taken from the
Info file itself.  If the Info does not contain the name, the basename
of the Info file is used.

@item --no-indent
@opindex --no-indent@r{, for @command{install-info}}
Suppress formatting of new entries into the @file{dir} file.

@item --quiet
@itemx --silent
@opindex --quiet@r{, for @command{install-info}}
@opindex --silent@r{, for @command{install-info}}
Suppress warnings, etc., for silent operation.

@item --remove
@opindex --remove@r{, for @command{install-info}}
Same as @samp{--delete}.

@item --remove-exactly
@opindex --remove-exactly@r{, for @command{install-info}}
Also like @samp{--delete}, but only entries if the Info file name
matches exactly; @code{.info} and/or @code{.gz} suffixes are
@emph{not} ignored.

@item --section=@var{sec}
@opindex --section=@var{sec}@r{, for @command{install-info}}
Put this file's entries in section @var{sec} of the directory.  If you
specify more than one section, all the entries are added in each of the
sections.  If you don't specify any sections, they are determined from
information in the Info file itself.  If the Info file doesn't specify
a section, the menu entries are put into the Miscellaneous section.

@item --section @var{regex} @var{sec}
@opindex --section @var{regex} @var{sec}@r{, for @command{install-info}}
Same as @samp{--regex=@var{regex} --section=@var{sec} --add-once}.

@code{install-info} tries to detect when this alternate syntax is used,
but does not always guess correctly.  Here is the heuristic that
@code{install-info} uses:
@enumerate
@item
If the second argument to @code{--section} starts with a hyphen, the
original syntax is presumed.

@item
If the second argument to @code{--section} is a file that can be
opened, the original syntax is presumed.

@item
Otherwise the alternate syntax is used.
@end enumerate

When the heuristic fails because your section title starts with a
hyphen, or it happens to be a file that can be opened, the syntax
should be changed to @samp{--regex=@var{regex} --section=@var{sec}
--add-once}.

@item --regex=@var{regex}
@opindex  --regex=@var{regex}@r{, for @command{install-info}}
Put this file's entries into any section that matches @var{regex}.  If
more than one section matches, all of the entries are added in each of the
sections.  Specify @var{regex} using basic regular expression syntax, more
or less as used with @command{grep}, for example.

@item --test
@opindex --test@r{, for @command{install-info}}
Suppress updating of the directory file.

@item --version
@opindex --version@r{, for @command{install-info}}
@cindex Version number, for install-info
Display version information and exit successfully.

@end table


@node Tag and Split Files
@section Tag Files and Split Files

@cindex Tag table
@cindex nonsplit Info file
@cindex split Info file
Info files always contain a @dfn{tag table}, to be able to jump to
nodes quickly.  Info files can be @dfn{nonsplit} (also called
@dfn{unsplit}) or @dfn{split}.

@cindex Indirect subfiles
If the Info file contains less than about 300,000 characters the
file should be nonsplit.  In that case, the tag table should
appear at the end of the Info file.  If the Texinfo file contains
more than about 300,000 characters, Texinfo processors split the
large Info file into shorter @dfn{indirect} subfiles of about
300,000 characters each.  With @command{texi2any}, splitting
may be prevented by @option{--no-split}, and the default size
of 300,000 characters may be modified with @option{--split-size}
(@pxref{Invoking @command{texi2any}}).

When a file is split, Info itself makes use of a shortened version of
the original file that contains just the tag table and references to
the files that were split off.  The split-off files are called
@dfn{indirect} files.

The split-off files have names that are created by appending @w{@samp{-1}},
@w{@samp{-2}}, @w{@samp{-3}} and so on to the output file name, specified
by the @code{@@setfilename} command or the input file name.  The shortened
version of the original file continues to have the name specified by
@code{@@setfilename} or the input file name.

At one stage in writing this document, for example, the Info file was saved
as the file @file{test-texinfo} and that file looked like this:

@example
@group
Info file: test-texinfo,    -*-Text-*-
produced by texinfo-format-buffer
from file: new-texinfo-manual.texinfo

^_
Indirect:
test-texinfo-1: 102
test-texinfo-2: 50422
@end group
@group
test-texinfo-3: 101300
^_^L
Tag table:
(Indirect)
Node: overview^?104
Node: info file^?1271
@end group
@group
Node: printed manual^?4853
Node: conventions^?6855
@dots{}
@end group
@end example

@noindent
(But @file{test-texinfo} had far more nodes than are shown here.)  Each of
the split-off, indirect files, @file{test-texinfo-1},
@file{test-texinfo-2}, and @file{test-texinfo-3}, is listed in this file
after the line that says @samp{Indirect:}.  The tag table is listed after
the line that says @samp{Tag table:}.

In the list of indirect files, the number following the file name
records the cumulative number of bytes in the preceding indirect
files, not counting the file list itself, the tag table, or any
permissions text in the first file.  In the tag table, the number
following the node name records the location of the beginning of the
node, in bytes from the beginning of the (unsplit) output.

If you are using @code{texinfo-format-buffer} to create Info files,
you may want to run the @code{Info-validate} command.  (The
@command{texi2any} command does such a good job on its own, you do not
need @code{Info-validate}.)  However, you cannot run the @kbd{M-x
Info-validate} node-checking command on indirect files.  For
information on how to prevent files from being split with
@code{texinfo-format-buffer} and how to validate the structure of the nodes,
see @ref{Using @code{Info-validate}}.


@node Info Format FAQ
@section Info Format FAQ

Here are some questions that have been frequently asked on
the project mailing lists and elsewhere.

@table @asis
@item Why when I run @samp{info @var{foo}} do I get the same output as @samp{man @var{foo}}?

Check that the Info manuals are installed.  Not all GNU/Linux
distributions install all the Info manuals by default.  This is
regrettable, as often the Info manual provides more information than
the provided man page.

@item Why not use HTML instead of Info?

Manuals are rarely written in the Info format itself, but are
generated from Texinfo source by the @command{texi2any} program.
@command{texi2any} can generate HTML as well as Info from Texinfo
source. You can also access and download HTML manuals from the GNU
website (@uref{https://www.gnu.org/manual/manual.html}).  Additionally,
some GNU/Linux distributions provide packages for the installation
of HTML manuals.

Info still has some advantages over HTML for locally installed
documentation.  The Info browsers support index lookup and support
for links between locally installed manuals in multiple locations.
It's important to have documentation installed locally on your machine
rather than relying on the Internet; this makes accessing documentation
more reliable, and ensures it matches installed versions of packages.
It's hoped that support for browsing locally installed Texinfo
documentation in some form of HTML can be improved in the future.


@item Why provide the command-line @command{info} program when the Emacs Info reader is better?

The Emacs Info reader can display images, and fully supports using
a mouse.  There are not many differences among the Info readers
besides that.  Command-line @command{info} can be configured
to change the default key bindings, as well as change the color
of cross-references and search results, and to enable mouse
scrolling support.  You should not need to be experienced with
the Emacs editor to use @command{info}.  (Some recommend another
program called @command{pinfo}, but this lacks in important
features like index lookup.)

Some prefer to be able to scroll through the entire manual at once (as
happens with man pages), rather than being limited to a single `node'
of content at once.  Of course, there is no accounting for taste,
but a single, unstructured block of text becomes more awkward as a
manual becomes longer and more complicated.  (However, if you really
want to, you can view an info manual all at once in the @command{less}
pager with @samp{info @var{foo} | less}.)

@item Why do I have `see' appearing in front of all of my links?

By default, Emacs Info mode either changes the marker @samp{*note} for
cross-references to `see', or hides it completely.  Command-line
@command{info} does the same if @code{hide-note-references} is set.
Unfortunately, there is no way to do this reliably, as both the @code{@@pxref}
and @code{@@ref} commands in Texinfo output this marker in the Info
output, and the `see' text is only appropriate for @code{@@pxref}.

@item Yes, but how do I get a plain link, with no extra markup?

You can't.  Info is a plain text format that is displayed mostly as-is
in the viewers, and without the @samp{*note} text there would be nothing
to mark text as a link.

For output formats such as HTML, you can use the @code{@@link} command
to produce a plain link.  @xref{@code{@@link}}.  This does not produce
a working cross-reference in Info output or in a printed copy of the
manual, though.


@item Why do lines containing links appear mysteriously short?

This due to Emacs (or @command{info} with @code{hide-note-references}
set to @samp{On}) hiding @samp{*note} strings, as mentioned above.

@item Can the Info format be extended to support fonts, colors or reflowable text?

Any extension would be incompatible with existing Info-viewing programs.
Extra markup added to Info files would be displayed to the user, making
files ugly and unreadable.

When Texinfo files are processed into Info files, information about
which Texinfo commands were used to markup text is lost.  Moreover,
it is not possible to reliably detect whether text can be reflowed
(e.g.@: a paragraph of prose), or whether line breaks should be kept
(e.g.@: a code sample, or poem).

Info's core purpose is to display documentation on text terminals.
If you want more, you are recommended to use the HTML output from
@command{texi2any} instead.

@end table


@node Generating HTML
@nodedescription Details on HTML output.
@chapter Generating HTML

@cindex Generating HTML
@cindex Outputting HTML

@command{texi2any} generates Info output by default, but given the
@option{--html} option, it will generate HTML, for web browsers and
other programs.  This chapter gives some details on such HTML output.

@command{texi2any} has many user-definable customization variables
with which you can influence the HTML output.  @xref{HTML Output
Customization}.  In particular, there is support for syntax
highlighting in @code{@@example} (@pxref{Syntax Highlighting}). You can also
write so-called @dfn{initialization files}, or @dfn{init files} for short, to
modify almost every aspect of HTML output.  Initialization files
contain code and are loaded by @option{--init-file} (@pxref{Invoking
@command{texi2any}}).

Some initialization files are maintained with Texinfo and installed
in the default case.  For example, @file{chm.pm} produces the intermediate
compressed HTML Help format files that can be subsequently converted to
the CHM format.

The documentation of @command{texi2any} HTML output adaptation using
customization files is in a separate manual.  @xref{,,, texi2any_api, GNU
Texinfo @command{texi2any} Output Customization}.


@node HTML Translation
@nodedescription Details of the HTML output.
@section HTML Translation

@cindex HTML translation

The HTML generated by @command{texi2any} generates standard HTML
output.  The output is intentionally quite plain for maximum portability
and accessibility.

You can customize the output via CSS (@pxref{HTML CSS}) or other
means (@pxref{HTML Output Customization}).  If you cannot accomplish
a reasonable customization, feel free to report that.

@cindex Navigation bar, in HTML output
@strong{Navigation bar:} By default, a navigation bar is inserted at the
start of each node, analogous to Info output.  If the
@samp{--no-headers} option is used, the navigation bar is only
inserted at the beginning of split files.  Header @code{<link>} elements
in split output support Info-like navigation with browsers which implement
this feature.

@cindex Escaping to HTML
@cindex Raw HTML
@strong{Raw HTML}: @command{texi2any} will include segments of Texinfo
source between @code{@@ifhtml} and @code{@@end ifhtml} in the HTML
output (but not any of the other conditionals, by default).  Source
between @code{@@html} and @code{@@end html} is passed without change
to the output (i.e., suppressing the normal escaping of input
@samp{<}, @samp{>} and @samp{&} characters which have special
significance in HTML)@.  @xref{Conditional Commands}.

@cindex HTML output @subentry browser compatibility
@strong{Standards}:
It is intentionally not our goal, and not even always possible, to pass
through every conceivable validation test without any diagnostics.
Different validation tests have different goals, often about pedantic
enforcement of some standard or another.  Our overriding goal is to
help users, not blindly comply with standards.

Please report output from an
error-free run of @command{texi2any} which has @emph{practical} browser
or EPUB reader portability problems as a bug (@pxref{Reporting Bugs}).

In practice, the HTML produced by @command{texi2any} is slowly adjusted
over time towards the latest HTML standard, while also trying to keep
compatibility with earlier produced HTML.  We use transitional markup
and try to be slow enough to give time for the diverse HTML readers
to adjust (and for standards to reincorporate useful features that were
dropped@dots{}).


@node HTML Splitting
@nodedescription How HTML output is split.
@section HTML Splitting
@cindex Split HTML output
@cindex HTML output @subentry split

When splitting output at nodes (which is the default),
@command{texi2any} writes HTML output into (basically) one output file
per Texinfo source @code{@@node}.

Each output file name is the node name with spaces replaced by
@samp{-}'s and special characters changed to @samp{_} followed by
their code point in hex (@pxref{HTML Xref}).  This is to make it
portable and easy to use as a file name.  In the unusual case of two
different nodes having the same name after this treatment, they are
written consecutively to the same file, with HTML anchors so each can
be referred to independently.

If @command{texi2any} is run on a system which does not distinguish
case in file names, nodes which are the same except for case (e.g.,
@samp{index} and @samp{Index}) will also be folded into the same
output file with anchors.  You can also pretend to be on a case
insensitive filesystem by setting the customization variable
@code{CASE_INSENSITIVE_FILENAMES}.

It is also possible to split at chapters or sections with
@option{--split} (@pxref{Splitting Output}).  In that case,
the file names are constructed after the name of the node associated
with the relevant sectioning command.  Also, unless
@option{--no-node-files} is specified, a redirection file is output
for every node in order to more reliably support cross-references to
that manual (@pxref{HTML Xref}).

When splitting, the HTML output files are written into a subdirectory.  The
subdirectory name is derived from the base name (that
is, any extension is removed), with @code{_html} appended. For example, HTML
output for @file{gcc.texi} would be written into a subdirectory
named @samp{gcc_html/}.  The subdirectory name is based on @code{@@setfilename}
or on the input file name (@pxref{Setting the Output File Name}).

@noindent In any case, the top-level output file within the directory
is always named @samp{index.html}.

Monolithic output (@code{--no-split}) is named according to
@code{@@setfilename}, if present (with any @samp{.info} extension replaced
with @samp{.html}), @code{--output} (the argument is used literally), or
based on the input file name as a last resort
(@pxref{Setting the Output File Name}).


@node HTML CSS
@nodedescription Influencing HTML output with Cascading Style Sheets.
@section HTML CSS
@cindex HTML, and CSS
@cindex CSS, and HTML output
@cindex Cascading Style Sheets, and HTML output

Cascading Style Sheets (CSS) is an Internet standard for
influencing the display of HTML documents: see
@uref{http://www.w3.org/Style/CSS/}.

By default, some CSS code is included to better implement the
appearance of some Texinfo environments.  For example:

@example
pre.display @{ font-family:inherit @}
@end example

The above tells the web browser to use the same font as the main
document inside @samp{<pre>} elements used for @code{@@display} environments.
By default, the HTML @samp{<pre>} command uses a monospaced font.

Please see the reference above for a full explanation of CSS.

You can influence the CSS in the HTML output with two
@command{texi2any} options: @option{--css-include=@var{file}} and
@option{--css-ref=@var{url}}.

The option @option{--css-ref=@var{url}} adds to each output HTML file
a @samp{<link>} tag referencing a CSS at the given @var{url}.  This
allows using external style sheets.

The option @option{--css-include=@var{file}} includes the contents
@var{file} in the HTML output, as you might expect.  However, the
details are somewhat tricky, as described in the following, to provide
maximum flexibility.

@cindex @samp{@@charset} specification, in CSS files
The CSS file first line may be a @samp{@@charset} directive.  If present,
this directive is used to determine the encoding of the CSS file.  The
line is not copied into the output.

@cindex @samp{@@import} specifications, in CSS files
The CSS file may begin with so-called @samp{@@import} directives,
which link to external CSS specifications for browsers to use when
interpreting the document.  Again, a full description is beyond our
scope here, but we'll describe how they work syntactically, so we can
explain how they are handled.

@cindex Comments, in CSS files
There can be more than one @samp{@@import}, but they have to come
first in the file, with only whitespace and comments interspersed, no normal
definitions.  Comments in CSS files are delimited by @samp{/* ... */}, as in
C@.  An @samp{@@import} directive must be in one of these two forms:

@example
@@import url(http://example.org/foo.css);
@@import "http://example.net/bar.css";
@end example

The crucial characters are the @samp{@@} at the beginning and
the semicolon terminating the directive.  When reading the CSS
file, any such @samp{@@}-directive is simply copied into the
output, as follows:

@itemize
@item If @var{file} contains only normal CSS declarations, it is
included after the default CSS, thus overriding it.

@item If @var{file} begins with @samp{@@import} specifications (see
below), then the @samp{import}'s are included first (they have to come
first, according to the standard), and then the default CSS is
included.  If you need to override the default CSS from an
@samp{@@import}, you can do so with the @samp{!@: important} CSS
construct, as in:
@example
pre.example @{ font-size: inherit ! important @}
@end example

@item If @var{file} contains both @samp{@@import} and inline CSS
specifications, the @samp{@@import}'s are included first, then
default CSS, and lastly the inline CSS from @var{file}.

@item Any @@-directive other than @samp{@@import} and @samp{@@charset}
is treated as a CSS declaration, meaning the default CSS is included
and then the rest of the file is prepended.
@end itemize

If the CSS file is malformed or erroneous, the output
is unspecified.  The meaning of the CSS file is not interpreted in
any way; the special @samp{@@} and @samp{;} characters are looked for
the text is blindly copied into the output.  Comments in the CSS
file may or may not be included in the output.

@vindex NO_CSS
@vindex INLINE_CSS_STYLE
By default, classes are added to the HTML elements and CSS rules
for these classes are output at the beginning of each HTML file.  Set
the @code{NO_CSS} customization variable to prevent classes being added and CSS
being used. Set @code{INLINE_CSS_STYLE} to have CSS code put in HTML
elements in the @code{style} attribute rather than at the beginning of
the output.

@vindex SHOW_BUILTIN_CSS_RULES
Since @command{texi2any} only inserts CSS code needed by the HTML
actually output, the full list of CSS code potentially inserted is
not visible in the output document.  To get the full list of CSS rules, call
@command{texi2any} with the @code{SHOW_BUILTIN_CSS_RULES} customization
variable set to output the built-in default CSS rules on the standard output
and exit, like:
@example
texi2any -c SHOW_BUILTIN_CSS_RULES=1
@end example


@node @code{@@documentdescription}
@nodedescription Document summary for the HTML output.
@section @code{@@documentdescription}: Summary Text
@anchor{documentdescription}@c old name

@cindex Document description
@cindex Description of document
@cindex Summary of document
@cindex Abstract of document
@cindex @code{<meta>} HTML tag, and document description
@findex documentdescription

When producing HTML output for a document, a @samp{<meta>} element
is written in the @samp{<head>} to give some idea of the
content of the document.  By default, this @dfn{description} is the
title of the document, taken from the @code{@@settitle} command
(@pxref{@code{@@settitle}}).  To change this, use the
@code{@@documentdescription} environment, as in:

@example
@@documentdescription
descriptive text.
@@end documentdescription
@end example

@noindent
This will produce the following output in the @samp{<head>} of the HTML:

@example
<meta name=description content="descriptive text.">
@end example


@node Generating EPUB
@nodedescription Details on the EPUB output.
@section Generating EPUB

@cindex EPUB, generating
@cindex Generating EPUB
@cindex Outputting EPUB

EPUB is a format designed for reading electronic books on portable
devices.  @command{texi2any} generated EPUB 3.3 in 2024.  An EPUB
file is a ZIP archive container, holding informative files as
well as the manual rendered in HTML.

@cindex @code{Archive::Zip}, for EPUB file output
@vindex EPUB_CREATE_CONTAINER_FILE @subentry @r{avoiding} @code{Archive::Zip} @r{dependency}
The generation of the EPUB file depends on the @code{Archive::Zip}
Perl module being installed.  This dependency is checked at runtime.
By default, trying to output EPUB without this dependency raises an
error.  However, if the EPUB output file is not generated, with the
customization variable @code{EPUB_CREATE_CONTAINER_FILE} set to 0, it is
not an error if @code{Archive::Zip} is not installed.

The @command{texi2any} tests related to EPUB generation do not require the
installation of @code{Archive::Zip}, as they set
@code{EPUB_CREATE_CONTAINER_FILE} to 0 and keep the directory containing
the files and directories needed for the EPUB file by setting the
@code{EPUB_KEEP_CONTAINER_FOLDER} customization variable to 1.


@node EPUB Output File and Directory
@subsection Container Directory and Output Files

@cindex Container directory for EPUB
@cindex EPUB Container directory
A directory containing the files and directories needed for the
EPUB format is created when outputting EPUB@.  The name of this
container directory is derived from the base name of the input file (that
is, any extension is removed), with @code{_epub_package} postpended.
If an output directory is specified, with @option{--output},
or with the @code{SUBDIR} customization variable,
the container directory is created in that directory instead of
the current directory.  At the beginning of a new run, the container
directory and all its contents are removed.  The container directory
is also removed after the final EPUB file has been generated in the
default case.

The HTML files produced from the Texinfo manual are output in subdirectories
of the container directory.  Image files referred to from the Texinfo manual,
if found, are copied to subdirectories of the container directory.

@cindex EPUB output file
The EPUB output file is a ZIP archive of the container directory.
The file name is derived from the base name, with the @code{.epub}
extension postpended.  If an output file is specified, with
@option{--output}, or with the @code{OUTFILE} customization function,
this file name is used instead.  The output EPUB file is never placed
in the directory specified by @option{--output} or @code{SUBDIR};
only the container directory is placed there, as explained just above.

@vindex EPUB_CREATE_CONTAINER_FILE
@vindex EPUB_KEEP_CONTAINER_FOLDER
The EPUB output file is not generated if the customization variable
@code{EPUB_CREATE_CONTAINER_FILE} is set to 0.  The container directory
is left after the final EPUB file has been generated if
@code{EPUB_KEEP_CONTAINER_FOLDER} is set.

@xref{Invoking @command{texi2any}}.


@node EPUB Cross-References
@nodedescription No cross-references in EPUB output.
@subsection EPUB Cross-References

The EPUB format does not support references from an EPUB file to
another EPUB file.  Therefore any references to ``external'' Texinfo
manuals should resolve to an external URL@:.  @command{texi2any}
produces these links with HTML cross-reference configuration
(@pxref{HTML Xref Configuration}).  Since the links in the
resulting EPUB are incorrect if no information is found for the
cross-references, @command{texi2any} issues a warning by default for
missing cross-references information.  If these warnings are unwanted,
set @code{CHECK_HTMLXREF} to 0.


@node EPUB Conformance
@subsection Achieving strict EPUB conformance

By default, @command{texi2any} produces EPUB expected by conformance
checkers as far as possible.   You may still need to adjust your Texinfo
manual to achieve full conformance to:
@itemize
@item Make sure that references to external manuals resolve to URLs
(@pxref{EPUB Cross-References}).
@item Avoid Texinfo code more forgiving than XHTML.  In general
valid Texinfo is converted to valid XHTML, but there are exceptions.
For example, you should avoid nested references and nested sectioning
commands and references, content before @code{@@table}
first @code{@@item} and omitting the second column of @code{@@table}
@code{@@item}.
@item Remove spaces in Texinfo input file names.
@item Remove form feeds that end up in output.
@end itemize


@node EPUB HTML
@nodedescription Variables set internally.
@subsection HTML Generated for EPUB

The HTML generated for EPUB is XHTML conformant, UTF-8 encoded, and
formatted without the usual HTML navigation headers and footers.

@command{texi2any} achieves this internally by setting customization
variables, such as @code{USE_XML_SYNTAX}, @code{HEADERS} or
@code{OUTPUT_ENCODING_NAME}.  Some features of printed output are used
in EPUB@.  In particular, the Top node does not appear in the EPUB
output, while a title page is generated.  This is obtained by setting
@code{NO_TOP_NODE_OUTPUT}.  @xref{HTML Output Customization}.

The @code{OUTFILE} and @code{SUBDIR} customization variables values
correspond initially to the EPUB directory container and/or the
EPUB output file (@pxref{EPUB Output File and Directory}).  These
customization variables values are undefined or reset to the
locations in the container directory where the XHTML files are output
for the HTML generation.

This use of customization variables by @command{texi2any} is mentioned here
because resetting such variables is unusual; however, the variables reset
are used internally for the conversion, and should not interact with any
customization set by the user.


@node Syntax Highlighting
@c @nodedescription Using external programs.
@nodedescription Use syntax highlighting in code excerpts.
@section Code Examples Syntax Highlighting in HTML
@cindex @command{source-highlight}

@ignore
@cartouche
@quotation Warning
Source highlighting is experimental; feedback is welcomed.  The syntax
of @code{HIGHLIGHT_SYNTAX} is very likely to change in future release.
@end quotation
@end cartouche
@end ignore

@vindex HIGHLIGHT_SYNTAX
@vindex HIGHLIGHT_SYNTAX_DEFAULT_LANGUAGE
You can use the @code{HIGHLIGHT_SYNTAX} variable for
syntax highlighting of source code in @code{@@example} blocks
for the HTML output, with the help
of external software.  You can set @code{HIGHLIGHT_SYNTAX} to
one of several special values:

@table @code
@item highlight
Use @command{highlight} from
@url{http://www.andre-simon.de/doku/highlight/en/highlight.php}.
@item pygments
Use @command{pygmentize} from @url{https://pygments.org/}.
@item source-highlight
Use @command{source-highlight} (@pxref{,,,source-highlight, GNU Source-highlight}).
@end table

The first argument on an @code{@@example} line (@pxref{@code{@@example}})
gives the name of the language used for syntax highlighting.
@code{@@example} blocks without such an argument are only highlighted if
@code{HIGHLIGHT_SYNTAX_DEFAULT_LANGUAGE} if set, which variable gives the
language to use for highlighting such blocks.

If you use a value for @code{HIGHLIGHT_SYNTAX} that is not listed above,
it is a template for a command line that is executed to highlight code.
This gives you more control over the exact command-line options
used for the highlighting program, and allows you use other programs
than those listed above.  In this template, the name of the highlighted
language is substituted for occurrences of @samp{%l}, and @samp{%}
is substituted for @samp{%%}.  @command{texi2any} passes the content of
each @code{@@example} block (converted to simple text) on standard input,
and the highlighted HTML is read from the standard output.

For example, if you set @code{HIGHLIGHT_SYNTAX} to @samp{colorcode -l=%l} and
there is an @samp{@@example C++} block in the document, the @command{colorcode
-l=C++} command line is executed with the @samp{@@example} block passed
to the standard input of the executed command, and the result is read from the
standard output of the executed command.


@node HTML Xref
@nodedescription Standard algorithm for interoperability.
@c @nodedescription Cross-references in HTML output.
@section HTML Cross-references
@cindex HTML cross-references
@cindex Cross-references, in HTML output

Cross-references between Texinfo manuals in HTML format become standard
HTML @code{<a>} links.  This section describes the algorithm used,
so that Texinfo can cooperate with other programs, such as
@command{texi2html}, by writing mutually compatible HTML files.

This algorithm may or may not be used for links @emph{within} HTML
output for a Texinfo file.  Since no issues of compatibility arise in
such cases, we do not need to specify this.

We try to support references to such ``external'' manuals in both
monolithic and split forms.  A @dfn{monolithic} (mono) manual is
entirely contained in one file, and a @dfn{split} manual has a file
for each node.  (@xref{HTML Splitting}.)

@cindex Dumas, Patrice
The algorithm was primarily devised by Patrice Dumas in 2003--04.

@menu
* Link Basics:       HTML Xref Link Basics.
* Node Expansion:    HTML Xref Node Name Expansion.
* Command Expansion: HTML Xref Command Expansion.
* 8-bit Expansion:   HTML Xref 8-bit Character Expansion.
* Configuration:     HTML Xref Configuration.
@end menu


@node HTML Xref Link Basics
@subsection HTML Cross-reference Link Basics
@cindex HTML cross-references @subentry link basics

For our purposes, an HTML link consists of four components: a host
name, a directory part, a file part, and a target part.  We
always assume the @code{http} protocol.  For example:

@example
http://@var{host}/@var{dir}/@var{file}.html#@var{target}
@end example

The information to construct a link comes from the node name and
manual name in the cross-reference command in the Texinfo source
(@pxref{Cross References}), and from @dfn{external information}
(@pxref{HTML Xref Configuration}).

In the usual case of HTML manuals published on the World Wide Web, in
order to have working cross-references, external information is required
to define the values of @var{host} and @var{dir}.  This is detailed later on
(@pxref{HTML Xref Configuration}).

If no external information is available for a manual, then defaults are
used for @var{host} and @var{dir} which correspond to cross-reference
links among a collection of manuals located side-by-side on a single host.
In this case, @var{host} is hardwired to be the local host.  This could
either be the literal string @samp{localhost}, or be omitted entirely along
with @samp{http://}, according to the rules for HTML links.

The @var{dir} and @var{file} parts depend both on the relative split/mono
nature of the manual being processed, and on the manual to which
the cross-reference refers:

@itemize @bullet
@item
If the present manual is split, and the referent manual is also split,
the directory is @samp{../@var{referent}_html/} and the file is the
expanded node name (described later).

@item
If the present manual is split, and the referent manual is mono, the
directory is @samp{../} and the file is @file{@var{referent}.html}.

@item
If the present manual is mono, and the referent manual is split, the
directory is @file{@var{referent}_html/} and the file is the expanded node
name.

@item
If the present manual is mono, and the referent manual is also mono,
the directory is @file{./} (or just the empty string), and the file is
@file{@var{referent}.html}.

@end itemize

The underlying idea is that there is one directory for Texinfo
manuals in HTML, and a given @var{manual} is either available as a
monolithic file @file{@var{manual}.html}, or as a split subdirectory
@file{@var{manual}_html/*.html}.

Another rule, which only holds for file names, is that base file names
are truncated to 245 characters to allow for an extension to be
appended and still comply with the 255-character limit which is common
to many filesystems.
@c  Although technically this can be changed with the
@c @code{BASEFILENAME_LENGTH} customization variable (@pxref{File Names and Links
@c Customization for HTML}), doing so would make cross-manual references to such
@c nodes invalid.

Any directory part in the file name argument of the source cross
reference command is ignored.  Thus, @code{@@xref@{,,,../foo@}} and
@code{@@xref@{,,,foo@}} both use @samp{foo} as the manual name.  This
is because any such attempted hardwiring of the directory is very
unlikely to be useful for all the output formats that use the manual
name.

Finally, the @var{target} part is always the expanded node name.

Whether the present manual is output as split or mono is determined by
how you run @command{texi2any}; the default is to split, with the
@option{--no-split} option overriding this.

By default, @command{texi2any} generates links to a referent manual using
the same form as the present manual: if the present manual is generated
as split, then links to other manuals are to their split forms by default;
likewise for mono output.

However, the form of the referent manual (mono or split) should usually
be specified in a configuration file (@pxref{HTML Xref Configuration}).
This ensures that there is no mismatch between the format of the referent
manual that the generating software assumes, and the format it's actually
present in.


@node HTML Xref Node Name Expansion
@subsection HTML Cross-reference Node Name Expansion
@cindex HTML cross-references @subentry node name expansion
@cindex node name expansion, in HTML cross-references
@cindex expansion, of node names in HTML cross-references

As mentioned in the previous section, the key part of the HTML cross
reference algorithm is the conversion of node names in the Texinfo
source into strings suitable for XHTML identifiers and file names.  The
restrictions are similar for each: plain ASCII letters, numbers, and
the @samp{-} and @samp{_} characters are all that can be used.
(Although HTML anchors can contain most characters, XHTML is more
restrictive.)

Cross-references in Texinfo can refer either to nodes, anchors
(@pxref{@code{@@anchor}}) or float labels (@pxref{@code{@@float}}).
However, anchors and float labels are treated identically
to nodes in this context, so we'll continue to say ``node'' names for
simplicity.

A special exception: the Top node (@pxref{The Top Node}) is always
mapped to the file @file{index.html}, to match web server software.
However, the HTML @emph{target} is @samp{Top}.  Thus (in the split case):

@example
@@xref@{Top,,, emacs, The GNU Emacs Manual@}.
@result{} <a href="../emacs_html/index.html#Top">
@end example

@enumerate
@item
The standard ASCII letters (a-z and A-Z) are not modified.  All other
characters may be changed as specified below.

@item
The standard ASCII numbers (0-9) are not modified except when a number
is the first character of the node name.  In that case, see below.

@item
Multiple consecutive space, tab and newline characters are transformed
into just one space.

@item
Leading and trailing spaces are removed.

@item
After the above has been applied, each remaining space character is
converted into a @samp{-} character.

@item
Other ASCII 7-bit characters are transformed into @samp{_00@var{xx}},
where @var{xx} is the ASCII character code in (lowercase) hexadecimal.
This includes @samp{_}, which is mapped to @samp{_005f}.

@item
If the node name does not begin with a letter, the literal string
@samp{g_t} is prefixed to the result.  (Due to the rules above, that
string can never occur otherwise; it is an arbitrary choice, standing
for ``GNU Texinfo''.)  This is necessary because XHTML requires that
identifiers begin with a letter.

@end enumerate

For example:

@example
@@node A  node --- with _'%
@result{} A-node-_002d_002d_002d-with-_005f_0027_0025
@end example

Example translations of common characters:

@itemize @bullet
@item @samp{_} @result{} @samp{_005f}
@item @samp{-} @result{} @samp{_002d}
@item @samp{A  node} @result{} @samp{A-node}
@end itemize

On case-folding computer systems, nodes differing only by case will be
mapped to the same file.  In particular, as mentioned above, Top
always maps to the file @file{index.html}.  Thus, on a case-folding
system, Top and a node named `Index' will both be written to
@file{index.html}.  Fortunately, the targets serve to distinguish
these cases, since HTML target names are always case-sensitive,
independent of operating system.


@node HTML Xref Command Expansion
@subsection HTML Cross-reference Command Expansion
@cindex HTML cross-references @subentry command expansion

Node names may contain @@-commands (@pxref{Node Line Requirements}).
This section describes how they are handled.

First, comments are removed.

Next, any @code{@@value} commands (@pxref{@code{@@set @@value}}) and
macro invocations (@pxref{Invoking Macros}) are fully expanded.

Then, for the following commands, the command name and braces are removed,
and the text of the argument is recursively transformed:

@example
@@asis @@b @@cite @@code @@command @@dfn @@dmn @@dotless
@@emph @@env @@file @@i @@indicateurl @@kbd @@key
@@samp @@sansserif @@sc @@slanted @@strong @@sub @@sup
@@t @@U @@var @@verb @@w
@end example

In addition, the following commands are replaced by constant text, as
shown below.  If any of these commands have non-empty arguments, as in
@code{@@TeX@{bad@}}, it is an error, and the result is unspecified.
In this table, `(space)' means a space character and `(nothing)' means
the empty string.  The notation `U+@var{hhhh}' means Unicode code
point @var{hhhh} (in hex, as usual).

There are further transformations of many of these expansions to yield
the final file or other target name, such as space characters to
@samp{-}, etc., according to the other rules.

@multitable @columnfractions .3 .5
@item @code{@@(newline)}        @tab (space)
@item @code{@@(space)}          @tab (space)
@item @code{@@(tab)}            @tab (space)
@item @code{@@!}                @tab @samp{!}
@item @code{@@*}                @tab (space)
@item @code{@@-}                @tab (nothing)
@item @code{@@.}                @tab @samp{.}
@item @code{@@:}                @tab (nothing)
@item @code{@@?}                @tab @samp{?}
@item @code{@@@@}               @tab @samp{@@}
@item @code{@@@{}               @tab @samp{@{}
@item @code{@@@}}               @tab @samp{@}}
@item @code{@@LaTeX}            @tab @samp{LaTeX}
@item @code{@@TeX}              @tab @samp{TeX}
@item @code{@@arrow}            @tab U+2192
@item @code{@@bullet}           @tab U+2022
@item @code{@@comma}            @tab @samp{,}
@item @code{@@copyright}        @tab U+00A9
@item @code{@@dots}             @tab U+2026
@item @code{@@enddots}          @tab @samp{...}
@item @code{@@equiv}            @tab U+2261
@item @code{@@error}            @tab @samp{error-->}
@item @code{@@euro}             @tab U+20AC
@item @code{@@exclamdown}       @tab U+00A1
@item @code{@@expansion}        @tab U+21A6
@item @code{@@geq}              @tab U+2265
@item @code{@@leq}              @tab U+2264
@item @code{@@minus}            @tab U+2212
@item @code{@@ordf}             @tab U+00AA
@item @code{@@ordm}             @tab U+00BA
@item @code{@@point}            @tab U+22C6
@item @code{@@pounds}           @tab U+00A3
@item @code{@@print}            @tab U+22A3
@item @code{@@questiondown}     @tab U+00BF
@item @code{@@registeredsymbol} @tab U+00AE
@item @code{@@result}           @tab U+21D2
@item @code{@@textdegree}       @tab U+00B0
@item @code{@@tie}              @tab (space)
@end multitable

Quotation mark @@-commands (@code{@@quotedblright@{@}} and the like),
are likewise replaced by their Unicode values.  Normal quotation
@emph{characters} (e.g., ASCII ` and ') are not altered.
@xref{Inserting Quotation Marks}.

Any @code{@@acronym}, @code{@@abbr}, @code{@@email}, and
@code{@@image} commands are replaced by their first argument.  (For
these commands, all subsequent arguments are optional, and ignored
here.)  @xref{@code{@@acronym}}, and @ref{@code{@@email}}, and @ref{Images}.

Accents are handled according to the next section.

Any other command is an error, and the result is unspecified.


@node HTML Xref 8-bit Character Expansion
@subsection HTML Cross-reference 8-bit Character Expansion
@cindex HTML cross-references @subentry 8-bit character expansion
@cindex 8-bit characters, in HTML cross-references
@cindex Expansion of 8-bit characters in HTML cross-references
@cindex Transliteration of 8-bit characters in HTML cross-references

Usually, characters other than plain 7-bit ASCII are transformed into
the corresponding Unicode code point(s) in Normalization Form@tie{}C,
which uses precomposed characters where available.  (This is the
normalization form recommended by the W3C and other bodies.)  This
holds when that code point is @code{0xffff} or less, as it almost
always is.

These will then be further transformed by the rules above into the
string @samp{_@var{hhhh}}, where @var{hhhh} is the code point in hex.

For example, combining this rule and the previous section:

@example
@@node @@b@{A@} @@TeX@{@} @@u@{B@} @@point@{@}@@enddots@{@}
@result{} A-TeX-B_0306-_22C6_002e_002e_002e
@end example

Notice: 1)@tie{}@code{@@enddots} expands to three periods which in
turn expands to three @samp{_002e}'s; 2)@tie{}@code{@@u@{B@}} is a `B'
with a breve accent, which does not exist as a pre-accented Unicode
character, therefore expands to @samp{B_0306} (B with combining
breve).

When the Unicode code point is above @code{0xffff}, the transformation
is @samp{__@var{xxxxxx}}, that is, two leading underscores followed by
six hex digits.  Since Unicode has declared that their highest code
point is @code{0x10ffff}, this is sufficient.  (We felt it was better
to define this extra escape than to always use six hex digits, since
the first two would nearly always be zeros.)

This method works fine if the node name consists mostly of ASCII
characters and contains only few 8-bit ones.  But if the document is
written in a language whose script is not based on the Latin alphabet
(for example, Ukrainian), it will create file names consisting almost
entirely of @samp{_@var{xxxx}} notations, which is inconvenient and
all but unreadable.  To handle such cases, @command{texi2any} offers
the @option{--transliterate-file-names} command line option.  This
option enables @dfn{transliteration} of node names into ASCII
characters for the purposes of file name creation.
The transliteration is based on phonetic principles, which makes the
generated file names more easily understandable.

@cindex Normalization Form C, Unicode
For the definition of Unicode Normalization Form@tie{}C, see Unicode
report UAX#15, @uref{http://www.unicode.org/reports/tr15/}.  Many
related documents and implementations are available elsewhere on the
web.


@node HTML Xref Configuration
@nodedescription @file{htmlxref.cnf} and @file{htmlxref.d/*.cnf}.
@subsection HTML Cross-reference Configuration

@c the "HTML Xref Mismatch" was removed.  Placing the anchor here as
@c it is the most relevant node for that subject.
@anchor{HTML Xref Mismatch}

@pindex htmlxref.cnf
@pindex htmlxref.d/*.cnf
@cindex HTML cross-references @subentry configuration
@cindex Cross-reference configuration, for HTML
@cindex Configuration, for HTML cross-manual references

For other manuals published on the World Wide Web to be able to have
correct cross-references to your manual, the @var{host} and
@var{dir} parts of the cross-reference need to be known by Texinfo
converters when they produce HTML for those other manuals.
Similarly, for your manual in HTML format to have correct
cross-references to other manuals, @command{texi2any} needs to know
how to construct the URLs for other manuals.

@command{texi2any} reads a file named @file{htmlxref.cnf} and all the
files ending with the @file{.cnf} extension in the @file{htmlxref.d}
directory to gather information for cross-references to other manuals in HTML
output.  @file{htmlxref.cnf} and @file{htmlxref.d} are looked for in the
following directories, based on the
@url{https://specifications.freedesktop.org/basedir-spec/latest/, XDG Base
Directory Specification} with defaults based on installation directories:

@table @file
@item ./
(the current directory)

@item leading input file path directory
If there is a leading directory and it is not the current directory.
For example, if the input file is @file{some/dir/mymanual.texi},
@file{htmlxref.cnf} is searched for in @file{some/dir} and files matching
@file{some/dir/htmlxref.d/*.cnf} are read too.

@item ./.texinfo/
(under the current directory)

@item @env{XDG_CONFIG_HOME}/texinfo
(with @env{XDG_CONFIG_HOME} an environment variable)

@item ~/.config/texinfo/
(where @code{~} is the current user's home directory, only if
@env{XDG_CONFIG_HOME} is not set)

@item @var{sysconfdir}/xdg/texinfo/
(where @var{sysconfdir} is the system configuration directory
specified at compile-time, e.g., @file{/usr/local/etc})

@item @env{XDG_CONFIG_DIRS}/texinfo
(for each directory in the @code{:} delimited @env{XDG_CONFIG_DIRS}
environment variable)

@c @item /etc/xdg/texinfo/
@c (with @file{/etc/xdg} the default directory for @env{XDG_CONFIG_DIRS}
@c in the XDG Base Directory Specification)

@item @var{datadir}/texinfo/
(specified at compile time, e.g., @file{/usr/local/share})

@c @item @env{XDG_DATA_DIRS}/texinfo
@c (for each directory in the @code{:} delimited @env{XDG_DATA_DIRS} environment
@c variable)

@c @item /usr/local/share/texinfo/
@c (with @file{/usr/local/share} the first default directory for
@c @env{XDG_DATA_DIRS} in the XDG Base Directory Specification)

@c @item /usr/share/texinfo/
@c (with @file{/usr/share/} the second default directory for @env{XDG_DATA_DIRS}
@c in the XDG Base Directory Specification)
@end table

All files found are used, with earlier entries overriding later ones.
The Texinfo distribution includes files that are installed in
@file{@var{datadir}/texinfo/htmlxref.d}, in one of the last of the
above directories:

@table @file
@item Texinfo_GNU.cnf
Handles many GNU manuals.
@item Texinfo_nonGNU.cnf
Free manuals of non GNU projects.
@end table

You can use a local @file{htmlxref.cnf} to complete or correct the
default files from the Texinfo distribution.  This could be useful to
correct outdated data, or even to generate cross-references to local
files for some manuals.  Other software packages managing lists of manuals
following the HTML cross-references specification could install @file{.cnf}
files in @file{@var{datadir}/texinfo/htmlxref.d}.

The @code{HTMLXREF_MODE} customization variable can be set to modify how the
files are found.  For instance, if set to @samp{none}, no external information
is used.  @code{HTMLXREF_FILE} sets the file name to something else than
@file{htmlxref.cnf}.  @xref{HTML Xref Configuration Customization}.

The file is line-oriented.  Lines consisting only of whitespace are
ignored.  Comments are indicated with a @samp{#} at the beginning of a
line, optionally preceded by whitespace.  Since @samp{#} can occur in
URLs (like almost any character), it does not otherwise start a
comment.

Each non-blank non-comment line must be either a @dfn{variable
assignment} or @dfn{manual information}.

A variable assignment line looks like this:

@example
@var{varname} = @var{varvalue}
@end example

Whitespace around the @samp{=} is optional and ignored.  The
@var{varname} should consist of letters; case is significant.  The
@var{varvalue} is an arbitrary string, continuing to the end of the
line.  Variables are then referenced with @samp{$@{@var{varname}@}};
variable references can occur in the @var{varvalue}.

A manual information line looks like this:

@example
@var{manual} @var{keyword} @var{urlprefix}
@end example

@noindent
with @var{manual} the short identifier for a manual, @var{keyword}
being one of: @code{mono}, @code{node}, @code{section},
@code{chapter}, and @var{urlprefix} described below.  Variable
references can occur only in the @var{urlprefix}.  For example (used
in the canonical file):

@example
G = https://www.gnu.org
GS = $@{G@}/software
hello mono    $@{GS@}/hello/manual/hello.html
hello chapter $@{GS@}/hello/manual/html_chapter/
hello section $@{GS@}/hello/manual/html_section/
hello node    $@{GS@}/hello/manual/html_node/
@end example

@cindex monolithic manuals, for HTML cross-references
If the keyword is @code{mono}, @var{urlprefix} gives the host,
directory, and file name for @var{manual} as one monolithic file.

@cindex split manuals, for HTML cross-references
If the keyword is @code{node}, @code{section}, or @code{chapter},
@var{urlprefix} gives the host and directory for @var{manual} split
into nodes, sections, or chapters, respectively.

If @var{urlprefix} is omitted, the elements of the cross-references
correspond to cross-reference links among a collection of manuals located
side-by-side on a single host (@pxref{HTML Xref Link Basics}).  This
could be useful if you generate and publish a collection of manuals and
prefer linking to the generated manuals rather than to the versions found in
cross-references configurations shipped with Texinfo.

When @command{texi2any} is generating a link to another Texinfo manual,
it will prefer to use a line for the manual with the same
splitting option as the current output.  That is, when generating
monolithic output (@option{--no-split}), a @code{mono} URL will be
preferred; when generating output that is split by node, a @code{node}
URL will be preferred, etc.

If no information line with the preferred splitting option is present
for a given manual, then other lines for that manual can be used if
present.  Here is the full search order for each splitting option:

@example
node    @result{} node,    section, chapter, mono
section @result{} section, chapter, node,    mono
chapter @result{} chapter, section, node,    mono
mono    @result{} mono,    chapter, section, node
@end example

@opindex --node-files@r{, and HTML cross-references}
These section- and chapter-level cross-manual references can succeed
only when the target manual was created using @option{--node-files};
this is the default for split output.

At present, the @file{Texinfo_GNU.cnf} and @file{Texinfo_nonGNU.cnf} files
distributed with GNU Texinfo serve as the main resource to locate Texinfo HTML
manuals in the World Wide Web.  Since they are installed in a location used by
@command{texi2any}, information on HTML manuals found in these files will be
used for cross-references by default.

If you have additions or corrections to the files distributed with Texinfo,
please email @email{bug-texinfo@@gnu.org} as usual.  If you publish a Texinfo
HTML manual on the World Wide Web, having an up-to-date location listed in
@file{Texinfo_GNU.cnf} or @file{Texinfo_nonGNU.cnf} should ensure that all HTML
manuals generated by @command{texi2any} use this location for cross-references
automatically.  You can get the latest versions from
@url{https://ftpmirror.gnu.org/@/texinfo/@/htmlxref.d/@/Texinfo_GNU.cnf} and
@url{https://ftpmirror.gnu.org/@/texinfo/@/htmlxref.d/@/Texinfo_nonGNU.cnf}.
If you want to maintain a separate file distributed with Texinfo, please
email @email{bug-texinfo@@gnu.org} as well.


@node HTML Output Customization
@nodedescription Using customization variables.
@section HTML Output Customization

You can use many user-definable customization variables to influence
the HTML output.  @xref{HTML Customization Variables List} for the full list.
The possibilities offered by the customization variables, ranging from
overall document structure and HTML language variant to formatting of
specific constructs, should cover most needs not already satisfied
by CSS customization (@pxref{HTML CSS}).

If you ever need more control, you may be able to achieve this through
the use of initialization files, which are described in a separate
manual (@pxref{,,, texi2any_api, GNU Texinfo @command{texi2any} Output
Customization}).

@vindex TEXI2HTML
If the @code{TEXI2HTML} customization variable is set, the generated HTML is as
compatible as possible with @command{texi2html} (@pxref{@command{texi2html}}).
The effect of this variable is quite unusual, as it does not directly modify
the output, but sets a lot of other customization variables, including some
that may only be set in initialization files and are described in the
separate manual on @command{texi2any} Output Customization.  Unset in
the default case.


@node HTML Output Structure Customization
@subsection HTML Output Structure Customization

You can use customization variables to control the output of document
titles and tables of contents or other similar parts of documents.
Other variables have an effect on how @command{texi2any} views the
structure of a document and how output is split into output files.

@vindex SHOW_TITLE
@vindex USE_TITLEPAGE_FOR_TITLE
If @code{SHOW_TITLE} is @samp{undef}, the default, no title is
output at the start of the output.  If you set this variable,
by default the contents of @code{@@titlepage} (or output from
@code{@@maketitle}) is used for the title; unset
@code{USE_TITLEPAGE_FOR_TITLE} to get a simple title string.

@vindex NO_TOP_NODE_OUTPUT @subentry @r{for HTML}
By default, the HTML output is tailored for online viewing, with
the Top node being output as a top-level starting point for the reader.
You can set @code{NO_TOP_NODE_OUTPUT} to remove the Top node, which
results in output that may be more similar to the format of a printed
book.  By default, setting @code{NO_TOP_NODE_OUTPUT} also
outputs a title at the beginning of the document, although you
can override this by setting @code{SHOW_TITLE} to 0.

@vindex FORMAT_MENU @subentry @r{for HTML}
In each node, by default a list is output of subordinate sections
for navigation.  This corresponds to the @code{FORMAT_MENU} variable
being set to @samp{sectiontoc}.  To use menus instead to navigate in the
document (as in Info format; @pxref{Menus}), set @code{FORMAT_MENU} to
@samp{menu}.  Set @code{FORMAT_MENU} to @samp{menu_no_detailmenu} if you
want menus but no automatically generated @code{@@detailmenu} for
the Top master menu.  If you do not want either menus or subordinate sections
list for navigation to be output, set @code{FORMAT_MENU} to @samp{nomenu}.

@vindex CONTENTS_OUTPUT_LOCATION
By default, the table of contents for the entire document is output
at the end of the @code{@@top} section, to have the main location for
navigation in the whole document early on.  This corresponds to the
@code{CONTENTS_OUTPUT_LOCATION} variable set to @samp{after_top}.

You can have the table of contents output after the title (if
@code{SHOW_TITLE} is set) by setting @code{CONTENTS_OUTPUT_LOCATION}
to @samp{after_title}.
To output the table of contents at the end of the document or to a separate
file, if output is split, set @code{CONTENTS_OUTPUT_LOCATION}
to @samp{separate_element}.  You can also set
@code{CONTENTS_OUTPUT_LOCATION} to @samp{inline}: in this case,
the tables of contents are output where
the corresponding @@-command, for example @code{@@contents}, is used.

You may find it useful to set @code{CONTENTS_OUTPUT_LOCATION} when
@code{FORMAT_MENU} is set to @samp{menu} in order to use menus for
navigation.  In this case, there should already be a master menu in the
@code{@@top} section (@pxref{Master Menu Parts}), and so the reader of
your manual may not need a table of contents at the same location.

@vindex USE_NODES @subentry @r{for HTML}
Elementary units called @dfn{output units} are used for output, with each
output file containing the content for one or more output units, depending
on the value of @code{SPLIT} (described below).  Output units contain
the content associated with a node or a sectioning command.  In typical
Texinfo document sources, a node command is almost always associated
with an immediately following sectioning command.

The customization variable @code{USE_NODES} determines whether the
node or the sectioning command is considered to be the main command.
By default, nodes are used as the main component for the separation of
output units.  You can set @code{USE_NODES} to false to preferentially
use sectioning to decide where output units are separated.
When sections are the main components of output units, ``isolated'' nodes
not directly associated with a sectioning command are associated with
the following sectioning command, while sectioning commands without
nodes constitute output units.  Conversely, when nodes are the main
components of output units, isolated sections not associated with nodes
are associated with the previous node, and isolated nodes are
output units.

@vindex USE_NODE_DIRECTIONS
By default, the @code{USE_NODES} setting also affects whether next,
up and prev links in node headers link to nodes or sections, with nodes
used if true, and sections used if false.  You can override this using
the @code{USE_NODE_DIRECTIONS} variable (default value is undefined).
Note that this setting does not determine the link string, only where the
links points to; see @ref{Three Arguments, , xrefautomaticsectiontitle}
for the link string customization.  If nodes and sections are
systematically associated, this customization has no practical effect.

@vindex SPLIT @subentry @r{for HTML}
By default, each output unit is output in a separate file.  You can change this
with the @option{--split} command-line option, which is equivalent to
setting the @code{SPLIT} variable.  @code{SPLIT} can take the values
@samp{chapter}, @samp{section}, or @samp{node}, or be set to an empty
string to indicate non-split output.  @xref{Splitting Output}.

@vindex DO_ABOUT
@vindex PROGRAM_NAME_IN_ABOUT
You can add a special @dfn{About} element explaining how to navigate by
setting @code{DO_ABOUT}, set to 0 in the default case (no About element).
If @code{PROGRAM_NAME_IN_ABOUT} is also set, output the program name and
miscellaneous related information in the About special element; default
false.

@vindex MONOLITHIC
In the case of non-split output, by default only one file is output
which contains any About elements (with @code{DO_ABOUT}) and tables of
contents elements (with @code{CONTENTS_OUTPUT_LOCATION} set to
@samp{separate_element}).  If you prefer such special elements to be
separate, set @code{MONOLITHIC} to 0 to output special elements to
separate files.


@node File Names and Links Customization for HTML
@subsection File Names and Links Customization for HTML

There are customization variables to control output file names, and
to customize hyperlinks output within output files.

@c file names

@vindex PREFIX @subentry @r{for HTML}
@vindex SUBDIR @subentry @r{for HTML}
@vindex EXTENSION @subentry @r{for HTML}
@vindex CASE_INSENSITIVE_FILENAMES
You can specify the output file names with more control than
merely the command line option @option{--output} (@pxref{Invoking
@command{texi2any}}). The @code{PREFIX} customization
variable overrides the base name of the file given by @code{@@setfilename} or
the file name and should not contain any directory components.  To alter
intermediate directories, use the @code{SUBDIR} customization variable.
Finally, you may also override the extension with the customization variable
@code{EXTENSION}.  This variable should be @code{undef} if no extension is to
be added.  If you set @code{CASE_INSENSITIVE_FILENAMES}, file names are
constructed as if the filesystem were case insensitive.  In that case,
one file name is used for all files differing only by case.

@vindex TOP_FILE
Furthermore, the customization variable @code{TOP_FILE} overrides
the output file name for the top element.  This is, in general,
only taken into account when output is split.

@vindex USE_ACCESSKEY
If @code{USE_ACCESSKEY} is set, the @code{accesskey} attribute
is used to provide keyboard shortcuts on some navigation hyperlinks.
@kbd{n} is used for links to the next node or section, @kbd{p} for links to
the previous node or section, and @kbd{u} for up direction links.  In the
default case, this customization variable value is @code{undef}, and set
automatically based on output document split, to avoid setting @code{accesskey}
to multiple values in the same HTML page (@pxref{HTML Splitting}).


@c internal links

There are customization variables that are specific to particular
types of link:

@table @emph
@item Cross-reference command links
@vindex XREF_USE_NODE_NAME_ARG
If the second argument of a cross-reference command is set, it is displayed
as hyperlink text (@pxref{Two Arguments}).  Otherwise the
@code{XREF_USE_NODE_NAME_ARG} customization variable is used to determine the
hyperlink text.  If set to@tie{}1, use the node name (first) argument in
cross-reference @@-commands for the text displayed as the hyperlink.  If set
to@tie{}0, use the node name if @code{USE_NODES} is set, otherwise the section
name.  If set to @samp{undef}, use the first argument in preformatted
environments, otherwise use the node name or section name depending on
@code{USE_NODES}.  The default is @samp{undef}.

@item Links to floats
@vindex XREF_USE_FLOAT_LABEL
If you set @code{XREF_USE_FLOAT_LABEL} (default is off), the float label
is used instead of the type followed by the float number
(@pxref{@code{@@float}}).

@item Links to nodes or sections for index entries
@vindex NODE_NAME_IN_INDEX
In @code{@@printindex} formatting, two links are output: a link to the index
entry, and a link to the root @@-command containing the index entry.  The
@code{NODE_NAME_IN_INDEX} customization variable specifies whether the node or
section should be used for the link to the root @@-command.  If true, use node
names in index entries, otherwise use section names.  If undefined, use
the @code{USE_NODES} value to determine which root @@-command to prefer.
Default is undefined.

@item Menu links
@vindex NODE_NAME_IN_MENU
Node names are used in menu entries links by default.  Set
@code{NODE_NAME_IN_MENU} to false to use section names instead.

@item Table of contents links
@vindex SHORT_TOC_LINK_TO_TOC
If a main Table of contents and a Short table of contents are both present, the
cross-references in the Short table of contents link to the corresponding
Table of Contents entries in the default case.  Set
@code{SHORT_TOC_LINK_TO_TOC} to 0 to link to the sectioning commands instead.

@vindex TOC_LINKS
If you set @code{TOC_LINKS}, links from headings to toc entries are created;
default false.

@item Top node Up direction link
@vindex IGNORE_REF_TO_TOP_NODE_UP
By default no Up reference is generated for the Top node.  You can set
@code{IGNORE_REF_TO_TOP_NODE_UP} so that any references to the Top Up node
(by default, @samp{(dir)}) appearing in other cross-references are also
ignored.  @code{IGNORE_REF_TO_TOP_NODE_UP} is not set in the default case.
(@xref{TOP_NODE_UP}.)

@vindex TOP_NODE_UP_URL
@vindex TOP_NODE_UP @subentry @r{for HTML}
If the manual is referred to in a web page together with other manuals,
it may be relevant to link to that page.  Set
@code{TOP_NODE_UP_URL} to the URL used for Top node up references.
If @code{TOP_NODE_UP_URL} is set, the value of @code{TOP_NODE_UP}
is used for the hyperlink text, with @samp{(dir)} as default.
@code{TOP_NODE_UP} can be used in attribute, so should not contain any element.

For example, in the GNU project @url{https://www.gnu.org/manual/} collects
links to most GNU manuals; therefore @code{TOP_NODE_UP_URL} is best
specified as @code{/manual/} if the manual will be installed on
@code{www.gnu.org}.

@xref{First Node} for more about the Top node pointers.

@item images links
@vindex IMAGE_LINK_PREFIX
If @code{IMAGE_LINK_PREFIX} is set, the associated value is prepended to
the image file links; default unset.  This could be useful if image files are
in a specific subdirectory.
@end table

@c Cross references

@anchor{HTML Xref Configuration Customization}
Cross-references between HTML manuals are specified precisely
(@pxref{HTML Xref}).  Customization of manual locations is provided
through the @file{htmlxref.cnf} and @file{htmlxref.d/*.cnf} files
(@pxref{HTML Xref Configuration}).

@vindex CHECK_HTMLXREF
Default directories and file names are used for cross-reference target
manuals not found through HTML Xref Configuration (@pxref{HTML Xref Link
Basics}).  By default, a warning is given for each external manual not in
the HTML Xref configuration files.  If you do not want warnings about such
manuals, you should set @code{CHECK_HTMLXREF} to @samp{0}.  This could
be relevant, for example, if you know that manuals are installed locally.

@vindex HTMLXREF_MODE
@vindex HTMLXREF_FILE
@vindex EXTERNAL_CROSSREF_SPLIT
@cindex HTML cross-references @subentry configuration customization
You can use customization variables to specify the HTML Xref
Configuration more precisely.
By default, the file name used for HTML Xref configuration
and the @file{htmlxref.d} directory are searched for in directories,
files in @file{htmlxref.d} with the @file{.cnf} extension and all the files
used for HTML Xref configuration found are used.
You can set the @code{HTMLXREF_MODE} customization variable to modify how
cross-references to other manuals information is determined.
If @code{HTMLXREF_MODE} is set to @samp{file}, the file name is directly used
as the source of information.  If @code{HTMLXREF_MODE} is set to @samp{none}
no information is used.  The default case is obtained with @code{HTMLXREF_MODE}
not defined or set to any other value.  The @code{HTMLXREF_FILE} customization
variable sets the file used for HTML Xref configuration to another value than
the default, @file{htmlxref.cnf}.  If @code{HTMLXREF_FILE} contains directories,
it is loaded if found, but is not searched for in directories.  By default, the
distant manual is considered to be split or monolithic based on the splitting
of the manual being output.  You can set it explicitly, instead, by setting
@code{EXTERNAL_CROSSREF_SPLIT}.

@cindex Cross-references customization, in HTML
There are also customization variables that modify various other
aspects of cross-references:

@itemize @bullet
@vindex TOP_NODE_FILE_TARGET
@item You can set the file name used for the Top node in cross-references by
setting the @code{TOP_NODE_FILE_TARGET} customization variable value;
default is @file{index.html}.

@vindex EXTERNAL_DIR
@item You specify a base directory for external
manuals with @code{EXTERNAL_DIR}; in the default case, there is none.

@vindex EXTERNAL_CROSSREF_EXTENSION
@item Similarly, you set the file extension for cross-references to other
manuals with @code{EXTERNAL_CROSSREF_EXTENSION}. @c , which, if unset, is based on
@c @code{EXTENSION}.

@end itemize

@noindent However, in general use of these will make cross-manual
references ``invalid'' in the sense that the generated URL will not link
to the external manual, unless this manual was itself also produced
using the corresponding customization. It is therefore, in general,
better to use HTML Xref Configuration only.

@vindex BASEFILENAME_LENGTH
You can change the maximum length of a base file name
for internal cross-references by setting @code{BASEFILENAME_LENGTH}; by
default, the base file names are truncated to 245 characters.
@c (@pxref{HTML Xref Link Basics}).



@node Customization of Navigation and Headers
@subsection Customization of Navigation and Headers

@vindex HEADERS @subentry @r{for HTML}
Headers and footers with a navigation panel are output in the default
case.  If you use @option{--no-headers}, or if the customization variable
@code{HEADERS} is unset, the navigation panel is only inserted at the
beginning of split files.

@vindex USE_LINKS
By default, @code{<link>} elements are generated in the
HTML @code{<head>} to specify relationships between the HTML page
and other resources, for example the Top node, the next node or
the table of contents.  Unset @code{USE_LINKS} to avoid those elements.

@vindex SECTION_NAME_IN_TITLE
The @code{<title>} and the document description in @code{<head>}
are based on @code{@@settitle} (@pxref{@code{@@settitle}}).
If the manual is split, the node name is also added to this HTML title.
Set @code{SECTION_NAME_IN_TITLE} to use the argument of the associated
chapter structuring command instead of the node name.

@vindex OUTPUT_ENCODING_NAME @subentry @r{for HTML}
By default, if an input encoding is set (typically through
@code{@@documentencoding}), this information is used to set the output
encoding name, otherwise the output encoding is based on the default encoding.
A @samp{<meta>} tag is output, in the @samp{<head>} section of the HTML, to
specify the output encoding.  @xref{@code{@@documentencoding}}.  To set
the output encoding explicitly, set @code{OUTPUT_ENCODING_NAME}.  The
specified encoding should be a normalized charset name usable in HTML,
typically one of the preferred IANA encoding names.

@vindex WORDS_IN_PAGE
When output is split at nodes (@pxref{HTML Splitting}), the
@code{WORDS_IN_PAGE} customization variable value specifies the approximate
minimum page length at which a navigation panel is placed at the bottom of a
page.  It is not possible for you to calibrate this value very precisely
for exact results: this is because the count of words used for the check
is based on the HTML output for the node so far (including any navigation
bar at the top of the page), which yields a value somewhat greater
than the number of words that would be visible to the user in their
web browser.

The appearance of the navigation panel is affected by the following
customization variables, all false in the default case:

@vtable @code
@item DATE_IN_HEADER
Put the document generation date in the header.

@item HEADER_IN_TABLE
Use tables for header formatting rather than a simple @samp{<div>}.

@item ICONS
Use icons for the navigation panel.

@item PROGRAM_NAME_IN_FOOTER
If set, output the program name and miscellaneous related information in the
page footers.

@item VERTICAL_HEAD_NAVIGATION
If set, a vertical navigation panel is used.
@end vtable

@cindex Initialization file, HTML icon direction buttons
Setting @code{ICONS} is necessary but not sufficient to get icons
for direction buttons, since no button image is specified in the
default case.  In addition, you need to set the @code{ACTIVE_ICONS}
and @code{PASSIVE_ICONS} customization variables.  You can only do this
using an initialization file (@pxref{Invoking @command{texi2any}}).
@xref{,,, texi2any_api, GNU Texinfo @command{texi2any} Output Customization}.


@node HTML Features Customization
@subsection HTML Features Customization

@vindex USE_XML_SYNTAX
@cindex DOCTYPE customization
@vindex DOCTYPE @subentry @r{for HTML}
By default HTML is generated, but you can set @code{USE_XML_SYNTAX}
in order to generate XML compatible code.  The main difference is
that @samp{/>} instead of @samp{>} ends tags such as @code{<img>} or
@code{<link>} that do not have a closing tag (such tags create so-called
@dfn{void elements}).

To set the @dfn{DOCTYPE}, set the @code{DOCTYPE} customization variable.
The default is the simple DTD-less DOCTYPE used for HTML5.

You can set an XML compatible file beginning instead:
@example
@command{texi2any} --html my_manual.texi -c USE_XML_SYNTAX \
   -c DOCTYPE='<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html>'
@end example

You could also set the DOCTYPE to HTML 4.01 Transitional:
@example
@command{texi2any} --html my_manual.texi -c DOCTYPE=\
'<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
  "http://www.w3.org/TR/html4/loose.dtd">'
@end example

@vindex USE_ISO
@vindex USE_NUMERIC_ENTITY @subentry @r{for HTML}
@vindex OUTPUT_CHARACTERS @subentry @r{for HTML}
By default, entities are used for doubled single-quote characters
(@pxref{Inserting Quotation Marks}), and @samp{---} and @samp{--}
(@pxref{Conventions}).  Set @code{USE_ISO} to @samp{0} in the unlikely case
that you want a simpler output.
By default textual entities are used when possible.  Set
@code{USE_NUMERIC_ENTITY} to use numeric entities only.
Set @code{OUTPUT_CHARACTERS} to output accented characters based on
the output encoding instead of entities.

@vindex NO_CUSTOM_HTML_ATTRIBUTE
By default a custom attribute, as allowed by the standard, is
used to provide the target manual name in cross-references.
If it is not desirable, for example to generate strict XHTML, you can
set @code{NO_CUSTOM_HTML_ATTRIBUTE} to prevent custom attributes being
output.

@vindex COPIABLE_LINKS
Copiable links are output for link targets for the definition commands
(@pxref{Definition Commands}), table commands (@pxref{Two-column
Tables}) where an index entry is defined and headings.  A link appears
as a `@U{00B6}'
@c pilcrow sign
sign that appears when you hover the mouse pointer over the heading text.
Unset @code{COPIABLE_LINKS} to prevent copiable links output.


@node Customization of Inserted HTML Code
@subsection Customization of Inserted HTML Code

There are variables to set the HTML code inserted at various points
in the output.

@vindex CLOSE_QUOTE_SYMBOL @subentry @r{for HTML}
@vindex OPEN_QUOTE_SYMBOL @subentry @r{for HTML}
Opening quote and closing quotes needed, e.g.@: for @code{@@samp} output,
are set to:

@table @asis
@item @code{&lsquo;} and @code{&rsquo;}
By default, with @code{OPEN_QUOTE_SYMBOL} and @code{CLOSE_QUOTE_SYMBOL}
undefined.

@item @code{&#8216;} and @code{&#8217;}
If you set @code{USE_NUMERIC_ENTITY}.

@item An opening and closing quote character
If you set @code{OUTPUT_CHARACTERS} and the output
encoding includes that character.

@item @code{OPEN_QUOTE_SYMBOL} and @code{CLOSE_QUOTE_SYMBOL}
If you set those customization variables.
@end table

@vindex DEFAULT_RULE
@vindex BIG_RULE
To change the HTML code for breaks (horizontal rule) inserted in various
contexts, set @code{DEFAULT_RULE}, which is
used for most horizontal separators output in the resulting HTML,
and set @code{BIG_RULE} for the wider separator sometimes used.

@c Arguments are HTML content to be inserted at certain points in the output.
@vindex HTML_ROOT_ELEMENT_ATTRIBUTES
@vindex EXTRA_HEAD
@c @vindex AFTER_BODY_OPEN
@cindex @code{<head>} block, adding to
@vindex BODY_ELEMENT_ATTRIBUTES
You can set @code{HTML_ROOT_ELEMENT_ATTRIBUTES} to add attributes to
the @code{<html>} element.
You can define the variable @code{EXTRA_HEAD} to add text within the
@code{<head>} HTML element.  Similarly, the value of
@code{AFTER_BODY_OPEN} is added just after @code{<body>} is output.
These variables are empty by default.

@cindex @code{<body>} tag, attributes of
You can set the attributes of the @code{<body>} element by defining the
customization variable @code{BODY_ELEMENT_ATTRIBUTES}.
By default, the @samp{lang} attribute is set to the document language
(@pxref{Setting the language}).

@vindex PRE_BODY_CLOSE
You can define the variable @code{PRE_BODY_CLOSE} to add text just
before the HTML @code{</body>} element.  Nothing is added by default.

Similarly, the following variables allow for some useful control of the
formatting of the table of contents and the short table of contents:

@vtable @code
@item BEFORE_TOC_LINES
Inserted before the table of contents text.

@item AFTER_TOC_LINES
Inserted after the table of contents text.

@item BEFORE_SHORT_TOC_LINES
Inserted before the short table of contents text.

@item AFTER_SHORT_TOC_LINES
Inserted after the short table of contents text.

@end vtable
At the time of writing, the default values of these variables are set to
opening and closing tags for a @code{<div>} element enclosing the
tables of contents.

@ignore
Could be an example, but would need either to specify as command-line
arguments, which would be cumbersome, or requires knowing about init
files
@c output valid XHTML XML 1.0 Document
@example
texinfo_set_from_init_file('HTML_ROOT_ELEMENT_ATTRIBUTES',
                           'xmlns="http://www.w3.org/1999/xhtml"');
texinfo_set_from_init_file('NO_CUSTOM_HTML_ATTRIBUTE', 1);
texinfo_set_from_init_file('USE_XML_SYNTAX', 1);
texinfo_set_from_init_file('DOCTYPE', '<?xml version="1.0" encoding="UTF-8"?>'."\n"
                                      .'<!DOCTYPE html>');
texinfo_set_from_init_file('USE_NUMERIC_ENTITY', 1);
texinfo_set_from_init_file('OUTPUT_ENCODING_NAME', 'utf-8');
@end example

@end ignore

@node HTML Customization of Specific Output
@subsection HTML Customization of Specific Output

The output of specific constructs is customizable.

@c Header levels

In HTML, heading levels translate to @samp{<h@var{n}>} elements
where @var{n} is the heading level.  The following header levels are
customizable:

@vtable @code
@item CHAPTER_HEADER_LEVEL
Header formatting level used for chapter level sectioning
commands; default @samp{2}.

@item FOOTNOTE_END_HEADER_LEVEL
@itemx FOOTNOTE_SEPARATE_HEADER_LEVEL
Header formatting level used for the footnotes header with
the `end' footnotestyle or for the `separate' footnotestyle; default @samp{4}.
@xref{Footnote Styles}.

@item MAX_HEADER_LEVEL
Maximum header formatting level used (higher header
formatting level numbers correspond to lower sectioning levels);
default @samp{4}.

@end vtable


@c Menu  Options for the output of @@menu, as well as indices.
@c Output of other constructs

You may modify the appearance of various constructs by setting:

@vtable @code
@item DEF_TABLE
If set, a @code{<table>} construction for @code{@@deffn}
and similar @@-commands is used (looking more like the @TeX{} output),
instead of definition lists; default false.

@item INDENTED_BLOCK_COMMANDS_IN_TABLE
If set, use tables for indentation of indented block commands; default
false.

@item INDEX_ENTRY_COLON
Symbol used between the index entry and the associated node or section;
default is an empty string.

@item MENU_ENTRY_COLON
Symbol used between the menu entry and the description; default
@samp{:}.

@item MENU_SYMBOL
Symbol used in front of menu entries when node names are used
for menu entries formatting; default is undefined and set to
@code{&bull;} if @code{USE_NUMERIC_ENTITY} is not set, and to
@code{&#8217;} if set.

@item NUMBER_FOOTNOTES
@itemx NO_NUMBER_FOOTNOTE_SYMBOL
By default footnotes are numbered.  With @option{--no-number-footnotes} or if
@code{NUMBER_FOOTNOTES} is set to 0, a @samp{*} is used instead, or the
@code{NO_NUMBER_FOOTNOTE_SYMBOL} customization variable value, if set.
@end vtable


@node HTML Customization for Math
@subsection HTML Customization for Math

@vindex HTML_MATH
@cindex HTML output @subentry math @subentry customization
You can select various methods to render math in HTML (@pxref{Inserting Math}).
This is controlled by the @code{HTML_MATH} customization variable.
By default, the customization variable is unset and the HTML output
is only emphasized.  You may select other options in order to display
properly formatted mathematics.  For some of these options, if you
set @option{--iftex}, @code{@@tex} sections are converted to HTML, and if you
set @option{--iflatex} @code{@@latex} sections are converted to HTML.

@table @code
@item l2h
Use the @command{latex2html} program to produce
image files for mathematical material.

@command{latex2html} will process @LaTeX{} math in math commands,
including @TeX{} math compatible with @LaTeX{}.
@command{latex2html} is used to translate @code{@@tex}
and @code{@@latex} sections to HTML if the corresponding sections
are not ignored.  Note that @command{latex2html} can only process @LaTeX{},
including when processing @code{@@tex} sections.

Processing with @command{latex2html} should leave files in the
output directory, with @samp{-l2h} in their name, in particular
a cache file to avoid redoing translation to HTML if already done.

@xref{@command{latex2html} Customization Variables}.

@item mathjax
@anchor{MathJax scripts}
Inserts references in the output files to MathJax scripts to format
mathematics.  The MathJax option requires JavaScript to be enabled in the
browser to work.

MathJax handles @LaTeX{} math, including commonly used @TeX{}
math compatible with @LaTeX{}.  Some specific constructs
(for example some uses of @code{\text}) are not supported, but this should
not be a practical issue.

If math commands are actually processed, a JavaScript license web label is
generated for MathJax scripts (@pxref{JavaScript license web labels}).

@xref{MathJax Customization Variables}.

@item t4h
Use the @command{tex4ht} program to produce HTML for mathematical material.

@command{tex4ht} will process @LaTeX{} math in math commands,
including @TeX{} math compatible with @LaTeX{}.
@command{tex4ht} is used to translate @code{@@tex} and @code{@@latex}
sections to HTML if the sections are not ignored.  The @code{@@tex} sections
are processed in @TeX{} mode, while the @code{@@latex} sections are
processed as @LaTeX{}.

Processing with @command{tex4ht} should leave files in the
output directory, with @samp{_tex4ht} in their name.

@xref{@command{tex4ht} Customization Variables}.

@end table

@vindex CONVERT_TO_LATEX_IN_MATH
By default, with @code{CONVERT_TO_LATEX_IN_MATH} undefined,
setting @code{HTML_MATH} also sets @code{CONVERT_TO_LATEX_IN_MATH}.
In that case Texinfo @@-commands inside @code{@@math} and @code{@@displaymath}
are converted to @LaTeX{}, before converting the @code{@@math} or
@code{@@displaymath} to HTML.


@node MathJax Customization Variables
@subsubsection MathJax Customization Variables

This table lists the customization variables which can be used when
MathJax is being used, which will be the case when @code{HTML_MATH}
is set to @samp{mathjax}.

@vtable @code
@item MATHJAX_CONFIGURATION
Data to add to the global @samp{MathJax} configuration object.
Specify as a comma-separated list of
@code{@var{component}: @{ @var{name}: @var{value}, @dots{} @}}
pairs.

For example, you could set @code{MATHJAX_CONFIGURATION} to

@example
options: @{ enableMenu: false @},
loader: @{
    load: [\'[tex]/physics\'],
    versionWarnings: false
@},
tex: @{
  packages: @{\'[+]\': [\'physics\']@}
@}
@end example

@noindent to disable the MathJax right-click menu, and to load the
MathJax @code{physics} extension.
(See @uref{https://docs.mathjax.org/en/latest/options/index.html,
Configuring MathJax} in the MathJax documentation.)

If you override any of the defaults for this configuration output by
@command{texi2any} you should make sure that your new settings align
with the HTML output produced by @command{texi2any}.

@item MATHJAX_SCRIPT
URL of the MathJax component file (e.g.@: @file{tex-svg.js}) you are using.
@command{texi2any} provides a default value for this variable, but you
are encouraged to host this file yourself on your website so that you are
not dependent on others' hosting.

@item MATHJAX_SOURCE
A URL of the full source code in its preferred form for modification,
or instructions for obtaining such source code, for the component file
named by @code{MATHJAX_SCRIPT}.  `Preferred form for modification'
means that this should not be in a `minified' form.  Used in the
license labels page (@pxref{JavaScript license web labels}).

Again, @command{texi2any} provides a default value for this variable,
but you are encouraged to host the source code for MathJax and its
dependencies yourself.  This is in order to make the source code
available reliably, and to reduce you and your users' dependence on
others' distribution systems.
@end vtable


@node @command{latex2html} Customization Variables
@subsubsection @command{latex2html} Customization Variables

This table lists the customization variables which can be used when 
@command{latex2html} is being used to convert @code{@@math},
@code{@@displaymath}, @code{@@latex} and @code{@@tex} sections for HTML@.
These customization variables are relevant only if @code{HTML_MATH} is set to
@samp{l2h}.

To actually convert @code{@@tex} sections, @option{--iftex} should be used,
and to actually convert @code{@@latex} sections, @option{--iflatex} should be
used.

@vtable @code
@item L2H_CLEAN
If set, the intermediate files generated in relation with @command{latex2html}
are removed; default true.

@item L2H_FILE
If set, the given file is used as @command{latex2html}'s init file; default
unset.

@item L2H_HTML_VERSION
The HTML version used in the @command{latex2html} call; default unset.

@item L2H_L2H
The program invoked as @command{latex2html}; default is @code{latex2html}.

@item L2H_SKIP
If set to a true value, the actual call to @command{latex2html} is skipped;
previously generated content is reused instead.  If set to 0, the cache is not
used at all.  If set to @samp{undef}, the cache is used for as many @TeX{}
fragments as possible and for any remaining the command is run.  The default is
@samp{undef}.

@item L2H_TMP
Set the directory used for temporary files.  None of the file name components
in this directory name may start with @samp{.}; otherwise, @command{latex2html}
will fail (because of @command{dvips}).  The default is the empty string, which
means the current directory.
@end vtable


@node @command{tex4ht} Customization Variables
@subsubsection @command{tex4ht} Customization Variables

This table lists the customization variables which can be used when
@command{tex4ht} is being used to convert @code{@@math}, @code{@@displaymath},
@code{@@tex} and @code{@@latex} sections for HTML@.  These customization
variables are relevant only if @code{HTML_MATH} is set to @samp{t4h}.

To actually convert @code{@@tex} sections, @option{--iftex} should be used,
and to actually convert @code{@@latex} sections, @option{--iflatex} should be
used.

@vtable @code
@item T4H_LATEX_CONVERSION
If set, the conversion type used for @code{@@latex} sections.  Possibilities
are @samp{latex}, @samp{tex} and @samp{texi}.  Set to @samp{latex} if not
defined.

@item T4H_MATH_CONVERSION
If set, the conversion type used for @code{@@math} and @code{@@displymath}.
Possibilities are @samp{latex}, @samp{tex} and @samp{texi}.  Set to @samp{tex}
if not defined.

@item T4H_TEX_CONVERSION
If set, the conversion type used for @code{@@tex} sections.  Possibilities
are @samp{latex}, @samp{tex} and @samp{texi}.  Set to @samp{tex} if not
defined.
@end vtable


@node JavaScript Interface and Licenses
@subsection JavaScript Interface and Licenses

@vindex INFO_JS_DIR
@cindex JavaScript browsing interface for HTML

You can add an experimental JavaScript browsing interface to the HTML
output by setting @code{INFO_JS_DIR} value to the name of a directory in
which to place the code for this interface.  For example,
@samp{texi2any --html -c INFO_JS_DIR=js @var{manual}.texi} places files in
a @samp{js} directory under the output.  This interface provides some of
the functionality of the Info browsers in a web browser, such as keyboard
navigation and index lookup.  This only works with non-split HTML output.

@anchor{JavaScript license web labels}
@cindex JavaScript license web labels page
@vindex JS_WEBLABELS
@vindex JS_WEBLABELS_FILE
By default, a @dfn{JavaScript license web labels page} is set up
to give licensing information and source code for any JavaScript used by
the HTML output
(see @uref{https://www.gnu.org/licenses/javascript-labels.html}).  To avoid
generating a JavaScript license web labels page, set @code{JS_WEBLABELS}
to @samp{omit}.  With @code{JS_WEBLABELS} set to @samp{generate}, the default,
generate a labels page at @code{JS_WEBLABELS_FILE}, @file{js_licenses.html}
in the default case, and link to it in the HTML output files.  With
@code{JS_WEBLABELS} set to @samp{reference}, link to the labels file given by
@code{JS_WEBLABELS_FILE} in the output, and do not generate a labels file.
This last setting is useful if you separately maintain a single labels
file for a larger website that includes your manual.

Labels files can be generated if @code{INFO_JS_DIR} is set, or if
@code{HTML_MATH} is set to @samp{mathjax} (@pxref{MathJax scripts}).


@node HTML Customization Variables List
@subsection HTML Customization Variables List

@c old name
@anchor{HTML Customization Variables}

This table lists the customization variables which apply to HTML output.

@table @code
@item AFTER_BODY_OPEN
Text added at the beginning of each HTML file; default unset.

@item AFTER_SHORT_TOC_LINES
@itemx AFTER_TOC_LINES
Text output after the short table of contents for
@code{AFTER_SHORT_TOC_LINES} and after the table of
contents for @code{AFTER_TOC_LINES} if set; otherwise, a default string is
used.  At the time of writing, a @code{</div>} element is closed.

In general, you should set @code{BEFORE_SHORT_TOC_LINES} if
@code{AFTER_SHORT_TOC_LINES} is set, and you should set
@code{BEFORE_TOC_LINES} if @code{AFTER_TOC_LINES} is set.

@item BASEFILENAME_LENGTH
The maximum length of a base file name for internal cross-references;
default 245.
@c Changing this would make cross-manual references to such long node
@c names invalid (@pxref{HTML Xref Link Basics}).

@item BEFORE_SHORT_TOC_LINES
@itemx BEFORE_TOC_LINES
If set, text output before the short table of contents for
@code{BEFORE_SHORT_TOC_LINES} and before the table of contents for
@code{BEFORE_TOC_LINES}, otherwise a default string is used.  At the time of
writing, a @code{<div ...>} element is opened.

In general you should set @code{AFTER_SHORT_TOC_LINES} if
@code{BEFORE_SHORT_TOC_LINES} is set, and you should set
@code{AFTER_TOC_LINES} if @code{BEFORE_TOC_LINES} is set.


@item BIG_RULE
Rule used after and before the top element and before
special elements, but not for footers and headers; default
@code{<hr>}.

@cindex @code{<body>} text, customizing
@opindex lang@r{, HTML attribute}
@item BODY_ELEMENT_ATTRIBUTES
The @code{<body>} attributes text.  By default, sets the
HTML @code{lang} attribute to the document language
(@pxref{Setting the language}).

@item CASE_INSENSITIVE_FILENAMES
Construct output file names as if the filesystem were case
insensitive (@pxref{HTML Splitting}); default false.

@item CHAPTER_HEADER_LEVEL
Header formatting level used for chapter level sectioning
commands; default @samp{2}.

@item CHECK_HTMLXREF
Check that manuals which are the target of external
cross-references (@pxref{Four and Five Arguments}) are present in
@file{htmlxref.cnf} or @file{htmlxref.d/*.cnf} (@pxref{HTML Xref
Configuration}); default true.

@item CONTENTS_OUTPUT_LOCATION
If set to @samp{after_top}, output the contents at the end of the @code{@@top}
section.  If set to @samp{inline}, output the contents where the
@code{@@contents} and similar @@-commands are located.  If set to
@samp{separate_element} output the contents in separate elements, either at the
end of the document if not split, or in a separate file.  If set to
@samp{after_title} the tables of contents are output after the title; default
@samp{after_top}.

@item CONVERT_TO_LATEX_IN_MATH
If set, try to convert any Texinfo @@-commands inside @code{@@math} and
@code{@@displaymath} to @LaTeX{}, before converting the @code{@@math} or
@code{@@displaymath} to HTML.  Default @code{undef}.  If undefined,
set if @code{HTML_MATH} is set.

@item COPIABLE_LINKS
If set, output copiable links for the definition commands
(@pxref{Definition Commands}), table commands (@pxref{Two-column
Tables}) where an index entry is defined and headings.  A link appears
as a `@U{00B6}'
@c pilcrow sign
sign that appears when you hover the mouse pointer over the heading text.

@item DATE_IN_HEADER
Put the document generation date in the header; off by default.

@item DEF_TABLE
If set, a @code{<table>} construction for @code{@@deffn}
and similar @@-commands is used (looking more like the @TeX{} output),
instead of definition lists; default false.

@item DEFAULT_RULE
Rule used between element, except before and after the
top element, and before special elements, and for footers and headers;
default @code{<hr>}.

@item DO_ABOUT
If set to 0 never do an About special element;
if set to 1 always do an About special element;
default 0.
@c @xref{Output Elements Defined}.

@item EPUB_CREATE_CONTAINER_FILE
If set to 0, do not generate the EPUB output file.  Default is set
to 1.

@item EPUB_KEEP_CONTAINER_FOLDER
If set, keep the directory containing the directories and files
needed for EPUB@.   The EPUB output file is a ZIP archive of this
directory.  Default is not defined.  Set if not defined and @code{TEST} or
@code{DEBUG} is set. @xref{EPUB Output File and Directory}.

@item EXTERNAL_CROSSREF_SPLIT
For cross-references to other manuals, this determines if the other
manual is considered to be split or monolithic.  By default, it is set
based on the value of @code{SPLIT}.  @xref{HTML Xref}, and @pxref{HTML
Xref Configuration}.

@item EXTERNAL_DIR
Base directory for external manuals; default none.  It is
better to use the general external cross-reference mechanism
(@pxref{HTML Xref Configuration}) than this variable.

@item EXTERNAL_CROSSREF_EXTENSION
File extension for cross-references to other manuals.@c  If unset,
@c based on @code{EXTENSION}.

@item EXTRA_HEAD
Additional text appearing within @code{<head>}; default unset.

@item FOOTNOTE_END_HEADER_LEVEL
Header formatting level used for the footnotes header with
the `end' footnotestyle; default @samp{4}.  @xref{Footnote Styles}.

@item FOOTNOTE_SEPARATE_HEADER_LEVEL
Header formatting level used for the footnotes header with
the `separate' footnotestyle; default @samp{4}.  @xref{Footnote
Styles}.

@item HEADER_IN_TABLE
Use tables for header formatting rather than a simple
@code{<div>} element; default false.

@item HIGHLIGHT_SYNTAX
If set, @code{@@example} blocks with language information as first
argument are highlighted in the HTML output.  It is also possible to specify a
default for the language with @code{HIGHLIGHT_SYNTAX_DEFAULT_LANGUAGE}.  Syntax
highlighting requires an external program to generate the highlighted HTML.
The @code{HIGHLIGHT_SYNTAX} value allows to select a specific program.  The
possibilities are @code{source-highlight}, @code{highlight}, @code{pygments},
with any other value being concatenated to the language to generate the
command-line for the external program (@pxref{Syntax Highlighting}).

@item HIGHLIGHT_SYNTAX_DEFAULT_LANGUAGE
The default language used for syntax highlighting when there is no
language information.

@item HTML_MATH
Method to use to render @code{@@math} (@pxref{HTML Customization for Math}).
This can be unset, set to
@samp{mathjax} (@pxref{MathJax Customization Variables}),
set to @samp{l2h}, which uses @command{latex2html}
(@pxref{@command{latex2html} Customization Variables}), or set to
@samp{t4h}, which uses @command{tex4ht}
(@pxref{@command{tex4ht} Customization Variables}).  By default,
setting @code{HTML_MATH} also sets @code{CONVERT_TO_LATEX_IN_MATH}.

@item HTML_ROOT_ELEMENT_ATTRIBUTES
Use that string for the @code{<html>} HTML document root element.
Default undefined.

@item HTMLXREF_FILE
Set the file name used for cross-references to other manuals.  If
not defined, @file{htmlxref.cnf} is used (@pxref{HTML Xref Configuration}).
Not defined in the default case.  If @code{TEST} is set, @code{HTMLXREF_MODE}
is set to the default and @code{HTMLXREF_FILE} is not defined, information on
cross-references to other manuals is not used.

If @code{HTMLXREF_MODE} is set to @samp{file} the file name is directly used as
the source of information.  Otherwise the file name is searched for in
directories, and all the files found are used (@pxref{HTML Xref
Configuration}).  @file{htmlxref.d/*.cnf} files are also used in that case.


@item HTMLXREF_MODE
How cross-references to other manuals information is determined.
If set to @samp{none}, no information is used.  If set to @samp{file},
the information is determined from a file path, @file{htmlxref.cnf} in the
default case, or the value of @code{HTMLXREF_FILE}.  If not defined (the
default) or set to any other value, search for the @code{HTMLXREF_FILE} file
name and the @file{htmlxref.d} directory in directories and use all the
@code{HTMLXREF_FILE} files and files in the @file{htmlxref.d} directory with
the @file{.cnf} extension (@pxref{HTML Xref Configuration}).

@item ICONS
Use icons for the navigation panel; default false.

@item IMAGE_LINK_PREFIX
If set, the associated value is prepended to the image file
links; default unset.

@item INDENTED_BLOCK_COMMANDS_IN_TABLE
If set, use tables for indentation of indented block commands; default
false.

@item INDEX_ENTRY_COLON
Symbol used between the index entry and the associated node or section;
default is an empty string.

@item INFO_JS_DIR
(Experimental.)  Add a JavaScript browsing interface to the manual.
The value of the variable is the directory to place the code for this
interface, so you would run the program as e.g.@: @samp{texi2any --html
-c INFO_JS_DIR=js @var{manual}.texi} to place files in a @samp{js}
directory under the output.  This provides some of the functionality
of the Info browsers in a web browser, such as keyboard navigation
and index lookup.  This only works with non-split HTML output.

The interface should provide an acceptable fallback in functionality
if JavaScript or web browser features are not available.  However,
please be cautious when using this option, in case you do make your
documentation harder to access for some of your users.

@item IGNORE_REF_TO_TOP_NODE_UP
Ignore references to @code{TOP_NODE_UP}, the up node for the Top node.

@item INLINE_CSS_STYLE
Put CSS directly in HTML elements rather than at the
beginning of the output; default false.

@item JS_WEBLABELS
@itemx JS_WEBLABELS_FILE
Specify how to use a @dfn{JavaScript license web labels} page to
give licensing information and source code for any JavaScript used
in the HTML files for the manual.
(See @uref{https://www.gnu.org/licenses/javascript-labels.html}).

With the value @samp{generate} (the default), generate a labels page
at @code{JS_WEBLABELS_FILE}, and link to it in the HTML output files.
Only do this if actually referencing JavaScript files (either with
@code{HTML_MATH} set to @samp{mathjax}, or when using the experimental
JS browsing interface when @code{INFO_JS_DIR} is set).  With this
setting, @code{JS_WEBLABELS_FILE} must be a relative file name.

With the value @samp{reference}, link to the labels
file given by @code{JS_WEBLABELS_FILE} in the output, and do not
generate a labels file.  This setting is useful if you separately
maintain a single labels file for a larger website that includes
your manual.

With @samp{omit}, neither generate nor link to a labels file.

@item MAX_HEADER_LEVEL
Maximum header formatting level used (higher header
formatting level numbers correspond to lower sectioning levels);
default @samp{4}.

@item MENU_ENTRY_COLON
Symbol used between the menu entry and the description; default
@samp{:}.

@item MENU_SYMBOL
Symbol used in front of menu entries when node names are used
for menu entries formatting; default is undefined and set to
@code{&bull;} if @code{USE_NUMERIC_ENTITY} is not set, and to
@code{&#8217;} if set.

@item MONOLITHIC
Output only one file including the table of contents.  Set
by default, but only relevant when the output is not split.

@item NO_CSS
Do not use CSS; default false.  @xref{HTML CSS}.

@item NO_CUSTOM_HTML_ATTRIBUTE
Do not output HTML with custom attributes in elements; default false.

@item NO_NUMBER_FOOTNOTE_SYMBOL
Symbol used for footnotes if @code{NUMBER_FOOTNOTES} is false.
Default is @code{*}.

@item NODE_NAME_IN_INDEX
If true, use node names in index entries, otherwise prefer section names.
If undefined, use @code{USE_NODES} value in HTML.  Default is undefined.

@item NODE_NAME_IN_MENU
If set, use node names in menu entries, otherwise prefer section names;
default true.

@item PRE_BODY_CLOSE
If set, the given text will appear at the footer of each
HTML file; default unset.

@item PROGRAM_NAME_IN_ABOUT
Used when an About element is output.  If set, output the program
name and miscellaneous related information in About special element;
default false.

@item PROGRAM_NAME_IN_FOOTER
If set, output the program name and miscellaneous related
information in the page footers; default false.

@item SECTION_NAME_IN_TITLE
If set,  when output is split, use the argument of the chapter
structuring command (e.g., @code{@@chapter} or @code{@@section})
in the @code{<title>} instead of the argument to @code{@@node}.

@item SHORT_TOC_LINK_TO_TOC
If set, the cross-references in the Short table of contents links to the
corresponding Table of Contents entries, if a Table of Contents is output;
default true.

@item SHOW_BUILTIN_CSS_RULES
Output the built-in default CSS rules on the standard output and exit.

@item SHOW_TITLE
If set, output the title at the beginning of the document;
default @samp{undef}.  If set to @samp{undef}, setting
@code{NO_TOP_NODE_OUTPUT} also sets @code{SHOW_TITLE} for HTML.

@cindex compatibility, with @command{texi2html}
@item TEXI2HTML
Generate HTML and try to be as compatible as possible with
@command{texi2html}; default false.

@item TOC_LINKS
If set, links from headings to toc entries are created;
default false.

@item TOP_FILE
This file name may be used for the top-level file.  The extension is
set appropriately, if necessary.  This is used to override the default,
and is, in general, only taken into account when output is split, and
for HTML@.

@item TOP_NODE_FILE_TARGET
File name used for the Top node in cross-references;
default is @code{index.html}.

@item TOP_NODE_UP_URL
A URL used for Top node up references; the default is
@code{undef}, in that case no Top node Up reference is generated.
For overriding the Up pointer name in case @code{TOP_NODE_UP_URL} is set and
for other formats, see @code{TOP_NODE_UP} in @ref{Customization Variables for
Multiple Formats}.  @xref{File Names and Links Customization for HTML}.  For
more about the Top node pointers, @pxref{First Node}.

@cindex @code{accesskey} @subentry customization variable for
@item USE_ACCESSKEY
Use @code{accesskey} in cross-references; default @code{undef}. If
@code{undef}, set if the output is split.

@item USE_ISO
Use entities for doubled single-quote characters
(@pxref{Inserting Quotation Marks}), and @samp{---} and @samp{--}
(@pxref{Conventions}); default true.

@cindex @code{<link>} HTML tag, in @code{<head>}
@cindex @code{<head>} HTML tag, and @code{<link>}
@item USE_LINKS
Generate @code{<link>} elements in the HTML @code{<head>}
output; default true.

@item USE_NODE_DIRECTIONS
If true, use nodes to determine where next, up and prev
link to in node headers.  If false, use sections.  If undefined, use
@code{USE_NODES} value.  Default is undefined.  Note that this setting does not
determine the link string, only where the links points to; see @ref{Three
Arguments, , xrefautomaticsectiontitle} for the link string customization.  If
nodes and sections are systematically associated, this customization has no
practical effect.

@item USE_TITLEPAGE_FOR_TITLE
Use the full @code{@@titlepage} (or output from @code{@@maketitle}) as
the title, not a simple title string; default true.  Only relevant if
@code{SHOW_TITLE} is set.

@item USE_XML_SYNTAX
Use XML/XHTML compatible syntax.

@item VERTICAL_HEAD_NAVIGATION
If set, a vertical navigation panel is used; default false.

@cindex Navigation panel, bottom of page
@cindex Navigation footer
@item WORDS_IN_PAGE
When output is split by nodes, specifies the approximate
minimum page length at which a navigation panel is placed at the
bottom of a page.  To avoid ever having the navigation buttons at the
bottom of a page, set this to a sufficiently large number.  The
default is 200.

@item XREF_USE_FLOAT_LABEL
If set, for the float name in cross-references, use the
float label instead of the type followed by the float number
(@pxref{@code{@@float}}).  The default is off.

@item XREF_USE_NODE_NAME_ARG
Only relevant for cross-reference commands with no cross
reference name (second argument).  If set to@tie{}1, use the node name
(first) argument in cross-reference @@-commands for the text displayed
as the hyperlink.  If set to@tie{}0, use the node name if
@code{USE_NODES} is set, otherwise the section name.  If set to
@samp{undef}, use the first argument in preformatted environments,
otherwise use the node name or section name depending on
@code{USE_NODES}.  The default is @samp{undef}.

@end table


@node @@-Command Details
@nodedescription Details of the Texinfo @@-commands.
@appendix @@-Command Details

Here are the details of @@-commands: information about their syntax, a 
list of commands, and information about where commands can appear.


@node Command Syntax
@section @@-Command Syntax
@cindex @sortas{at} @@-commands @subentry syntax
@cindex Syntax, of @@-commands
@cindex Command syntax

Texinfo has the following types of @@-command:

@table @asis
@item 1. Brace commands
These commands start with @@ followed by a letter or a word, followed by an
argument within braces.  For example, the command @code{@@dfn} indicates
the introductory or defining use of a term; it is used as follows: @samp{In
Texinfo, @@@@-commands are @@dfn@{mark-up@} commands.}

@item 2. Line commands
These commands occupy an entire line.  The line starts with @@,
followed by the name of the command (a word); for example, @code{@@center}
or @code{@@cindex}.  If no argument is needed, the word is followed by
the end of the line.  If there is an argument, it is separated from
the command name by a space.  Braces are not used.

@findex end
@item 3. Block commands
These commands are written at the start of a line, with general text on
following lines, terminated by a matching @code{@@end} command on a
line of its own.  For example, @code{@@example}, then the lines of a
coding example, then @code{@@end example}.  Some of these block commands
take arguments as line commands do; for example, @code{@@enumerate A}
opening an environment terminated by @code{@@end enumerate}.  Here
@samp{A} is the argument.

@item 4. Symbol insertion commands with no arguments
These commands start with @@ followed by a word followed by a
left and right- brace.  These commands insert special symbols in
the document; they do not take arguments.  Some examples:
@code{@@dots@{@}} @result{} @samp{@dots{}}, @code{@@equiv@{@}}
@result{} @samp{@equiv{}}, @code{@@TeX@{@}} @result{} `@TeX{}', and
@code{@@bullet@{@}} @result{} @samp{@bullet{}}.

@item 5. Non-alphabetic commands
The names of commands in all of the above categories consist of
alphabetic characters, almost entirely in lowercase.  Unlike those, the
non-alphabetic commands consist of an @@ followed by a
punctuation mark or other character that is not part of the Latin
alphabet.  Non-alphabetic commands are almost always part of text
within a paragraph.  The non-alphabetic commands include @code{@@@@},
@code{@@@{}, @code{@@@}}, @code{@@.}, @code{@@@kbd{SPACE}}, and most of
the accent commands.

@item 6. Miscellaneous commands
There are a handful of commands that don't fit into any of the above
categories; for example, the obsolete command @code{@@refill}, which is
always used at the end of a paragraph immediately following the final
period or other punctuation character.  @code{@@refill} takes no
argument and does not require braces.  Likewise, @code{@@tab} used in a
@code{@@multitable} block does not take arguments, and is not followed 
by braces.
@end table

@cindex Braces and argument syntax
Thus, the alphabetic commands fall into classes that have
different argument syntaxes.  You cannot tell to which class a command
belongs by the appearance of its name, but you can tell by the
command's meaning: if the command stands for a glyph, it is in
class 4 and does not require an argument; if it makes sense to use the
command among other text as part of a paragraph, the command
is in class 1 and must be followed by an argument in braces.  The
non-alphabetic commands, such as @code{@@:}, are exceptions to the
rule; they do not need braces.

The purpose of having different syntax for commands is to make Texinfo
files easier to read, and also to help the GNU Emacs paragraph and
filling commands work properly.


@node Command List
@section @@-Command List
@cindex Alphabetical @@-command list
@cindex List of @@-commands
@cindex @sortas{at} @@-commands @subentry list of
@cindex Reference to @@-commands

Here is an alphabetical list of the @@-commands in Texinfo.  Square
brackets, @t{[}@w{ }@t{]}, indicate optional arguments; an ellipsis,
@samp{@dots{}}, indicates repeated text.

@table @code
@item @@@var{whitespace}
An @code{@@} followed by a space, tab, or newline produces a normal,
stretchable, interword space.  @xref{Multiple Spaces}.

@item @@!
Produce an exclamation point that ends a sentence (usually after an
end-of-sentence capital letter).  @xref{Ending a Sentence}.

@item @@"
@itemx @@'
Generate an umlaut or acute accent, respectively, over the next
character, as in @"o and @'o.  @xref{Inserting Accents}.

@item @@&
@itemx @@ampchar@{@}
Generate an ampersand.  @xref{Inserting an Ampersand}.

@item @@*
Force a line break.  @xref{Line Breaks}.

@item @@,@{@var{c}@}
Generate a cedilla accent under @var{c}, as in @,{c}.  @xref{Inserting
Accents}.

@item @@-
Insert a discretionary hyphenation point.  @xref{@code{@@- @@hyphenation}}.

@item @@.
Produce a period that ends a sentence (usually after an
end-of-sentence capital letter).  @xref{Ending a Sentence}.

@item @@/
Produces no output, but allows a line break.  @xref{Line Breaks}.

@item @@:
Tell printed output processors to refrain from inserting extra
whitespace after an immediately preceding period, question mark,
exclamation mark, or colon.  @xref{Not Ending a Sentence}.

@item @@=
Generate a macron (bar) accent over the next character, as in @=o.
@xref{Inserting Accents}.

@item @@?
Produce a question mark that ends a sentence (usually after an
end-of-sentence capital letter).  @xref{Ending a Sentence}.

@item @@@@
@itemx @@atchar@{@}
Insert an at sign, @samp{@@}.  @xref{Inserting an Atsign}.

@item @@\
@itemx @@backslashchar@{@}
Insert a backslash, @samp{\}; @code{@@backslashchar@{@}} works
anywhere, while @code{@@\} works only inside @code{@@math}.
@xref{Inserting a Backslash}, and @ref{Inserting Math}.

@item @@^
@itemx @@`
Generate a circumflex (hat) or grave accent, respectively, over the next
character, as in @^o and @`e.
@xref{Inserting Accents}.

@item @@@{
@itemx @@lbracechar@{@}
Insert a left brace, @samp{@{}.  @xref{Inserting Braces}.

@item @@@}
@itemx @@rbracechar@{@}
Insert a right brace, @samp{@}}.  @xref{Inserting Braces}.

@item @@~
Generate a tilde accent over the next character, as in @~N.
@xref{Inserting Accents}.

@item @@AA@{@}
@itemx @@aa@{@}
Generate the uppercase and lowercase Scandinavian A-ring letters,
respectively: @AA{}, @aa{}.  @xref{Inserting Accents}.

@item @@abbr@{@var{abbreviation}@}
Indicate a general abbreviation, such as `Comput.'.
@xref{@code{@@abbr}}.

@item @@acronym@{@var{acronym}@}
Indicate an acronym in all capital letters, such as `NASA'.
@xref{@code{@@acronym}}.

@item @@AE@{@}
@itemx @@ae@{@}
Generate the uppercase and lowercase AE ligatures, respectively:
@AE{}, @ae{}.  @xref{Inserting Accents}.

@item @@afivepaper
Change page dimensions for the A5 paper size.  @xref{A4 Paper}.

@item @@afourlatex
@itemx @@afourpaper
@itemx @@afourwide
Change page dimensions for the A4 paper size.  @xref{A4 Paper}.

@item @@alias @var{new}=@var{existing}
Make the command @samp{@@@var{new}} a synonym for the existing command
@samp{@@@var{existing}}.  @xref{@code{@@alias}}.

@item @@allowcodebreaks @var{true-false}
Control breaking at @samp{-} and @samp{_} in printed output.
@xref{@code{@@allowcodebreaks}}.

@item @@anchor@{@var{name}@}
Define @var{name} as the current location for use as a cross-reference
target.  @xref{@code{@@anchor}}.

@item @@appendix @var{title}
Begin an appendix.  The title appears in the table of contents.
@xref{@code{@@unnumbered @@appendix}}.

@item @@appendixsec @var{title}
@itemx @@appendixsection @var{title}
Begin an appendix section within an appendix.  The section title
appears in the table of contents.  @code{@@appendixsection} is
a longer spelling of the @code{@@appendixsec} command.
@xref{@code{@@unnumberedsec @@appendixsec @@heading}}.

@item @@appendixsubsec @var{title}
Begin an appendix subsection.  The title appears in the table of
contents.  @xref{@code{@@unnumberedsubsec @@appendixsubsec @@subheading}}.

@item @@appendixsubsubsec @var{title}
Begin an appendix subsubsection.  The title appears in the table of
contents.  @xref{@code{@@subsubsection}}.

@item @@arrow@{@}
Generate a right arrow glyph: @samp{@arrow{}}.  Used by default
for @code{@@click}.  @xref{Click Sequences}.

@item @@asis
Keep the argument as is.
Used following @code{@@table}, @code{@@ftable}, and @code{@@vtable} to
print the table's first column without highlighting (``as is'').
@xref{@code{@@asis}}.

@item @@author @var{author}
Set a manual author in the title page.  @xref{@code{@@title @@subtitle @@author}}.
Set a quotation author in @code{@@quotation}.  @xref{@code{@@quotation}}.

@item @@b@{@var{text}@}
Set @var{text} in a @b{bold} font, if possible.  @xref{Fonts}.

@item @@bullet@{@}
Generate a large round dot, @bullet{}, or the closest possible thing to one.
Often used with @code{@@itemize}.  @xref{@code{@@bullet}}.

@item @@bsixpaper
Change page dimensions for the B6 paper size.  @xref{A4 Paper}.

@item @@bye
Stop processing a file.  The processors do not see anything in the
input file following @code{@@bye}.  @xref{Ending a File}.

@item @@c @var{comment}
Begin a comment in Texinfo.  The rest of the line does not appear in
any output.  A synonym for @code{@@comment}.  @kbd{DEL} also
starts a comment.  @xref{Comments}.

@item @@caption
Define the full caption for a @code{@@float}.  @xref{@code{@@caption
@@shortcaption}}.

@item @@cartouche
Highlight an example or quotation by drawing a box with rounded
corners around it, if possible.  Pair with @code{@@end cartouche}.
@xref{@code{@@cartouche}}.

@item @@center @var{line-of-text}
Center the line of text following the command.
@xref{@code{@@titlefont @@center @@sp}}.

@item @@centerchap @var{line-of-text}
Like @code{@@chapter}, but centers the chapter title.  @xref{@code{@@chapter}}.

@item @@chapheading @var{title}
Print an unnumbered chapter-like heading, but omit from the table of
contents.  @xref{@code{@@majorheading @@chapheading}}.

@item @@chapter @var{title}
Begin a numbered chapter.  The chapter title appears in the table of
contents.  @xref{@code{@@chapter}}.

@item @@cindex @var{entry}
Add @var{entry} to the index of concepts.  @xref{Index Entries, ,
Defining the Entries of an Index}.

@item @@cite@{@var{reference}@}
Highlight the name of a book or other reference that has no companion
Info file.  @xref{@code{@@cite}}.

@item @@clear @var{flag}
Unset @var{flag}, preventing the Texinfo formatting commands from
formatting text between subsequent pairs of @code{@@ifset @var{flag}}
and @code{@@end ifset} commands, and preventing
@code{@@value@{@var{flag}@}} from expanding to the value to which
@var{flag} is set.  @xref{@code{@@set @@clear @@value}}.

@item @@click@{@}
Represent a single ``click'' in a GUI@.  Used within
@code{@@clicksequence}.  @xref{Click Sequences}.

@item @@clicksequence@{@var{action} @@click@{@} @var{action}@}
Represent a sequence of clicks in a GUI@.  @xref{Click Sequences}.

@item @@code@{@var{sample-code}@}
Indicate an expression, a syntactically complete token of a program,
or a program name.  @xref{@code{@@code}}.

@item @@codequotebacktick @var{on-off}
@itemx @@codequoteundirected @var{on-off}
Control output of @code{`} and @code{'} in code examples.
@xref{Inserting Quote Characters}.

@item @@comma@{@}
Insert a comma `,' character; only needed when a literal comma would
be taken as an argument separator.  @xref{Inserting a Comma}.

@item @@command@{@var{command-name}@}
Indicate a command name, such as @command{ls}.  @xref{@code{@@command}}.

@item @@comment @var{comment}
Begin a comment in Texinfo.  The rest of the line does not appear in
any output.  A synonym for @code{@@c}.
@xref{Comments}.

@item @@contents
Print a complete table of contents or specify that a table of content
should be output, for formats that may output a table of contents.
@xref{Contents, , Generating a Table of Contents}.

@item @@copying
Specify copyright holders and copying conditions for the document.  Pair
with @code{@@end copying}.  @xref{@code{@@copying}}.

@item @@copyright@{@}
Generate the copyright symbol @copyright{}.
@xref{@code{@@copyright}}.

@item @@defblock
Start a block containing definitions.  Pair with @samp{@@end defblock}.
@xref{Generic Definition Commands}.

@item @@defcodeindex @var{index-name}
Define a new index and its indexing command.  Print entries in an
@code{@@code} font.  @xref{New Indices, , Defining New Indices}.

@item @@defcv @var{category} @var{class} @var{name}
@itemx @@defcvx @var{category} @var{class} @var{name}
Format a description for a variable associated with a class in
object-oriented programming.  Takes three arguments: the category of
thing being defined, the class to which it belongs, and its name.
@xref{Definition Commands}.

@item @@deffn @var{category} @var{name} @var{arguments}@dots{}
@itemx @@deffnx @var{category} @var{name} @var{arguments}@dots{}
Format a description for a function, interactive command, or similar
entity that may take arguments.  @code{@@deffn} takes as arguments the
category of entity being described, the name of this particular
entity, and its arguments, if any.  @xref{Definition Commands}.

@item @@defindex @var{index-name}
Define a new index and its indexing command.  Print entries in a roman
font.  @xref{New Indices, , Defining New Indices}.

@item @@definfoenclose @var{newcmd}, @var{before}, @var{after}
Create a new command @code{@@@var{newcmd}} for online formats
that marks text by enclosing it in strings that precede and
follow the text.
@xref{@code{@@definfoenclose}}.

@item @@defivar @var{class} @var{instance-variable-name}
@itemx @@defivarx @var{class} @var{instance-variable-name}
Format a description for an instance variable in object-oriented
programming.  The command is equivalent to @samp{@@defcv @{Instance
Variable@} @dots{}}.  @xref{Definition Commands}.

@item @@defline @var{category} @var{name} @var{arguments}@dots{}
Use within a @code{@@defblock} environment to give the heading prototype
line for a symbol being defined.  This command does not
create any index entries.  @xref{Generic Definition Commands}.

@item @@defmac @var{macroname} @var{arguments}@dots{}
@itemx @@defmacx @var{macroname} @var{arguments}@dots{}
Format a description for a macro; equivalent to @samp{@@deffn Macro
@dots{}}.  @xref{Definition Commands}.

@item @@defmethod @var{class} @var{method-name} @var{arguments}@dots{}
@itemx @@defmethodx @var{class} @var{method-name} @var{arguments}@dots{}
Format a description for a method in object-oriented programming;
equivalent to @samp{@@defop Method @dots{}}.  @xref{Definition
Commands}.

@item @@defop @var{category} @var{class} @var{name} @var{arguments}@dots{}
@itemx @@defopx @var{category} @var{class} @var{name} @var{arguments}@dots{}
Format a description for an operation in object-oriented programming.
@code{@@defop} takes as arguments the name of the category of
operation, the name of the operation's class, the name of the
operation, and its arguments, if any.  @xref{Definition Commands}, and
@ref{Abstract Objects}.

@item @@defopt @var{option-name}
@itemx @@defoptx @var{option-name}
Format a description for a user option; equivalent to @samp{@@defvr
@{User Option@} @dots{}}.  @xref{Definition Commands}.

@item @@defspec @var{special-form-name} @var{arguments}@dots{}
@itemx @@defspecx @var{special-form-name} @var{arguments}@dots{}
Format a description for a special form; equivalent to @samp{@@deffn
@{Special Form@} @dots{}}.  @xref{Definition Commands}.

@item @@deftp @var{category} @var{name-of-type} @var{attributes}@dots{}
@itemx @@deftpx @var{category} @var{name-of-type} @var{attributes}@dots{}
Format a description for a data type; its arguments are the category,
the name of the type (e.g., @samp{int}) , and then the names of
attributes of objects of that type.  @xref{Definition Commands}, and
@ref{Data Types}.

@item @@deftypecv @var{category} @var{class} @var{data-type} @var{name}
@itemx @@deftypecvx @var{category} @var{class} @var{data-type} @var{name}
Format a description for a typed class variable in object-oriented programming.
@xref{Definition Commands}, and @ref{Abstract Objects}.

@item @@deftypefn @var{category} @var{data-type} @var{name} @var{arguments}@dots{}
@itemx @@deftypefnx @var{category} @var{data-type} @var{name} @var{arguments}@dots{}
Format a description for a function or similar entity that may take
arguments and that is typed.  @code{@@deftypefn} takes as arguments the
category of entity being described, the type, the name of the
entity, and its arguments, if any.  @xref{Definition Commands}.

@item @@deftypefnnewline @var{on-off}
Specifies whether return types for @code{@@deftypefn} and similar are
printed on lines by themselves; default is off.  @xref{Typed
Functions,, Functions in Typed Languages}.

@item @@deftypefun @var{data-type} @var{function-name} @var{arguments}@dots{}
@itemx @@deftypefunx @var{data-type} @var{function-name} @var{arguments}@dots{}
Format a description for a function in a typed language.
The command is equivalent to @samp{@@deftypefn Function @dots{}}.
@xref{Definition Commands}.

@item @@deftypeivar @var{class} @var{data-type} @var{variable-name}
@itemx @@deftypeivarx @var{class} @var{data-type} @var{variable-name}
Format a description for a typed instance variable in object-oriented
programming. @xref{Definition Commands}, and @ref{Abstract Objects}.

@item @@deftypeline @var{category} @var{data-type} @var{name} @var{arguments}@dots{}
Use within a @code{@@defblock} environment to give the heading prototype
line for a symbol being defined, with data types.  This command does not
create any index entries.  @xref{Generic Definition Commands}.

@item @@deftypemethod @var{class} @var{data-type} @var{method-name} @var{arguments}@dots{}
@itemx @@deftypemethodx @var{class} @var{data-type} @var{method-name} @var{arguments}@dots{}
Format a description for a typed method in object-oriented programming.
@xref{Definition Commands}.

@item @@deftypeop @var{category} @var{class} @var{data-type} @var{name} @var{arguments}@dots{}
@itemx @@deftypeopx @var{category} @var{class} @var{data-type} @var{name} @var{arguments}@dots{}
Format a description for a typed operation in object-oriented programming.
@xref{Definition Commands}, and @ref{Abstract Objects}.

@item @@deftypevar @var{data-type} @var{variable-name}
@itemx @@deftypevarx @var{data-type} @var{variable-name}
Format a description for a variable in a typed language.  The command is
equivalent to @samp{@@deftypevr Variable @dots{}}.  @xref{Definition
Commands}.

@item @@deftypevr @var{category} @var{data-type} @var{name}
@itemx @@deftypevrx @var{category} @var{data-type} @var{name}
Format a description for something like a variable in a typed
language---an entity that records a value.  Takes as arguments the
category of entity being described, the type, and the name of the
entity.  @xref{Definition Commands}.

@item @@defun @var{function-name} @var{arguments}@dots{}
@itemx @@defunx @var{function-name} @var{arguments}@dots{}
Format a description for a function; equivalent to
@samp{@@deffn Function @dots{}}.  @xref{Definition Commands}.

@item @@defvar @var{variable-name}
@itemx @@defvarx @var{variable-name}
Format a description for a variable; equivalent to @samp{@@defvr
Variable @dots{}}.  @xref{Definition Commands}.

@item @@defvr @var{category} @var{name}
@itemx @@defvrx @var{category} @var{name}
Format a description for any kind of variable.  @code{@@defvr} takes
as arguments the category of the entity and the name of the entity.
@xref{Definition Commands}.

@item @@detailmenu
Mark the (optional) detailed node listing in a master menu.
@xref{Master Menu Parts}.

@item @@dfn@{@var{term}@}
Indicate the introductory or defining use of a term.  @xref{@code{@@dfn}}.

@item @@DH@{@}
@itemx @@dh@{@}
Generate the uppercase and lowercase Icelandic letter eth, respectively:
@DH{}, @dh{}.  @xref{Inserting Accents}.

@item @@dircategory @var{dirpart}
Specify a category for the manual.  @xref{Directory Category}.

@item @@direntry
Begin the Info directory menu entry for this file.  Pair with
@code{@@end direntry}.  @xref{Installing Dir Entries}.

@item @@display
Begin a kind of example.  Like @code{@@example} (indent text, do not
fill), but do not select a new font.  Pair with @code{@@end display}.
@xref{@code{@@display}}.

@item @@displaymath
Format a block of math in ``display'' format.  @xref{Inserting Math}.
 
@item @@dmn@{@var{dimension}@}
Format a unit of measure, as in 12@dmn{pt}.  @xref{@code{@@dmn}}.

@item @@docbook
Enter DocBook completely.  Pair with @code{@@end docbook}.  @xref{Raw
Formatter Commands}.

@item @@documentdescription
Set the document description text, included in the HTML output.  Pair
with @code{@@end documentdescription}.  @xref{@code{@@documentdescription}}.

@item @@documentencoding @var{enc}
Declare the input encoding to be @var{enc}.
@xref{@code{@@documentencoding}}.

@item @@documentinfo
Start the document metadata block. Pair with @samp{@@end documentinfo}.
@xref{Document Metadata}.

@item @@documentlanguage @var{ll[_CC]}
Declare the document language as the two-character ISO-639 abbreviation
@var{ll} with optional country code @var{CC}.  @xref{Setting the language}.

@item @@documentlanguagevariant [@var{variant1}][, @var{variant2}][, @dots{}]
Declare a list of language variants on top of the main language.  An empty
argument unsets the language variants.  @xref{Setting the language}.

@item @@documentscript [@var{script}]
Declare the document script as the four letter @var{script} ISO@tie{}15924 script
code name or well-known alias. An empty argument unsets the script.
@xref{Setting the language}.

@item @@dotaccent@{@var{c}@}
Generate a dot accent over the character @var{c}, as in @dotaccent{o}.
@xref{Inserting Accents}.

@item @@dotless@{@var{i-or-j}@}
Generate dotless i (`@dotless{i}') and dotless j (`@dotless{j}').
@xref{Inserting Accents}.

@item @@dots@{@}
Generate an ellipsis, @samp{@dots{}}.
@xref{@code{@@dots}}.

@item @@email@{@var{address}[, @var{displayed-text}]@}
Indicate an electronic mail address.  @xref{@code{@@email}}.

@item @@emph@{@var{text}@}
Emphasize @var{text}.  @xref{Emphasis, , Emphasizing Text}.

@item @@end @var{environment}
Ends @var{environment}, as in @samp{@@end example}.  @xref{Formatting
Commands,,@@-commands}.

@item @@enddots@{@}
Generate an end-of-sentence ellipsis, like this: @enddots{}
@xref{@code{@@dots}}.

@item @@enumerate [@var{number-or-letter}]
Begin a numbered list, using @code{@@item} for each entry.
Optionally, start list with @var{number-or-letter}.  Pair with
@code{@@end enumerate}.  @xref{@code{@@enumerate}}.

@item @@env@{@var{environment-variable}@}
Indicate an environment variable name, such as @env{PATH}.
@xref{@code{@@env}}.

@item @@equiv@{@}
Indicate to the reader the exact equivalence of two forms with a
glyph: @samp{@equiv{}}.  @xref{@code{@@equiv}}.

@item @@error@{@}
Indicate to the reader with a glyph that the following text is
an error message: @samp{@error{}}.  @xref{@code{@@error}}.

@item @@errormsg@{@var{msg}@}
Report @var{msg} as an error to standard error, and exit unsuccessfully.
Texinfo commands within @var{msg} are expanded to plain text.
@xref{Conditionals}, and @ref{External Macro Processors}.

@item @@euro@{@}
Generate the Euro currency sign.  @xref{@code{@@euro}}.

@item @@evenfooting [@var{left}] @@| [@var{center}] @@| [@var{right}]
@itemx @@evenheading [@var{left}] @@| [@var{center}] @@| [@var{right}]
Specify page footings resp.@: headings for even-numbered (left-hand)
pages.  @xref{Custom Headings, ,
How to Make Your Own Headings}.

@item @@everyfooting [@var{left}] @@| [@var{center}] @@| [@var{right}]
@itemx @@everyheading [@var{left}] @@| [@var{center}] @@| [@var{right}]
Specify page footings resp.@: headings for every page.  Not relevant to
Info.  @xref{Custom Headings, , How to Make Your Own Headings}.

@item @@example
Begin an example.  Indent text, do not fill, and select fixed-width
font.  Pair with @code{@@end example}.  @code{@@example} accepts optional
arguments, separated by commas.  It is recommended to set the first argument to
the language of the example code.  @xref{@code{@@example}}.

@item @@exampleindent @var{indent}
Indent example-like environments by @var{indent} number of spaces
(perhaps 0).  @xref{@code{@@exampleindent}}.

@item @@exclamdown@{@}
Generate an upside-down exclamation point.  @xref{Inserting Accents}.

@item @@exdent @var{line-of-text}
Remove any indentation a line might have.  @xref{@code{@@exdent}}.

@item @@expansion@{@}
Indicate the result of a macro expansion to the reader with a special
glyph: @samp{@expansion{}}.  @xref{@code{@@expansion}}.

@item @@file@{@var{filename}@}
Highlight the name of a file, buffer, node, directory, etc.
@xref{@code{@@file}}.

@item @@finalout
Prevent @TeX{} from printing large black warning rectangles beside
over-wide lines.  @xref{Overfull hboxes}.

@item @@findex @var{entry}
Add @var{entry} to the index of functions.  @xref{Index Entries, ,
Defining the Entries of an Index}.

@item @@firstparagraphindent @var{word}
Control indentation of the first paragraph after section headers
according to @var{word}, one of `none' or `insert'.
@xref{@code{@@firstparagraphindent}}.

@item @@float
Environment to define floating material.  Pair with @code{@@end float}.
@xref{Floats}.

@item @@flushleft
@itemx @@flushright
Do not fill text; left (right) justify every line while leaving the
right (left) end ragged.  Leave font as is.  Pair with @code{@@end
flushleft} (@code{@@end flushright}).  @xref{@code{@@flushleft
@@flushright}}.

@item @@fonttextsize @var{10-11}
Change the size of the main body font in the printed output.
@xref{Fonts}.

@item @@footnote@{@var{text-of-footnote}@}
Enter a footnote, for a reference that documents or elucidates the
primary text.  Footnote text is printed at the bottom of the page
in printed output.  In other formats, footnote text can be output
in the same node, in a separate node, or simply be marked as
being footnote text.  @xref{Footnotes}.

@item @@footnotestyle @var{style}
Specify a footnote style, either @samp{end} for the end
node style or @samp{separate} for the separate style.  In the
separate style, footnotes are put in a separate node or file.
@xref{Footnote Styles}.

@item @@format
Begin a kind of example.  Like @code{@@display}, but do not indent.
Pair with @code{@@end format}.  @xref{@code{@@example}}.

@item @@frenchspacing @var{on-off}
Control spacing after punctuation.  @xref{@code{@@frenchspacing}}.

@item @@ftable @var{formatting-command}
Begin a two-column table, using @code{@@item} for each entry.
Automatically enter each of the items in the first column into the
index of functions.  Pair with @code{@@end ftable}.  The same as
@code{@@table}, except for indexing.  @xref{@code{@@ftable @@vtable}}.

@item @@geq@{@}
Generate a greater-than-or-equal sign, `@geq{}'.  @xref{@code{@@geq @@leq}}.

@item @@group
Disallow page breaks within following text.  Pair with @code{@@end
group}.  Ignored in Info.  @xref{@code{@@group}}.

@item @@guillemetleft@{@}
@itemx @@guillemetright@{@}
@item @@guillemotleft@{@}
@itemx @@guillemotright@{@}
@itemx @@guilsinglleft@{@}
@itemx @@guilsinglright@{@}
Double and single angle quotation marks: @guillemetleft{}
@guillemetright{} @guilsinglleft{} @guilsinglright{}.
@code{@@guillemotleft} and @code{@@guillemotright} are synonyms for
@code{@@guillemetleft} and @code{@@guillemetright}.  @xref{Inserting
Quotation Marks}.

@item @@H@{@var{c}@}
Generate the long Hungarian umlaut accent over @var{c}, as in @H{o}.

@item @@hashchar@{@}
Insert a hash `#' character; only needed when a literal hash would
introduce @code{#line} directive.  @xref{Inserting a Hashsign}, and
@ref{External Macro Processors}.

@item @@heading @var{title}
Print an unnumbered section-like heading, but omit from the table of
contents.  @xref{@code{@@unnumberedsec @@appendixsec @@heading}}.

@item @@headings @var{on-off-single-double}
Turn page headings on or off, and/or specify single-sided or double-sided
page headings for printing.  @xref{@code{@@headings}}.

@item @@headitem
Begin a heading row in a multitable.  @xref{Multitable Rows}.

@item @@headitemfont@{@var{text}@}
Set @var{text} in the font used for multitable heading rows; mostly
useful in multitable templates.  @xref{Multitable Rows}.

@item @@html
Enter HTML completely.  Pair with @code{@@end html}.  @xref{Raw
Formatter Commands}.

@item @@hyphenation@{@var{hy-phen-a-ted words}@}
Explicitly define hyphenation points.  @xref{@code{@@- @@hyphenation}}.

@item @@i@{@var{text}@}
Set @var{text} in an @i{italic} font, when possible.  @xref{Fonts}.

@item @@ifclear @var{txivar}
If the Texinfo variable @var{txivar} is not set, format the following
text.  Pair with @code{@@end ifclear}.  @xref{@code{@@set @@clear
@@value}}.

@item @@ifcommanddefined @var{txicmd}
@itemx @@ifcommandnotdefined @var{txicmd}
If the Texinfo code @samp{@@@var{txicmd}} is (not) defined, format the
follow text.  Pair with the corresponding @code{@@end ifcommand...}.
@xref{Testing for Texinfo Commands}.

@item @@ifdocbook
@itemx @@ifepub
@itemx @@ifhtml
@itemx @@ifinfo
@itemx @@iflatex
@itemx @@ifplaintext
@itemx @@ifxml
Begin text that will appear only in the given output format.
@code{@@ifinfo} output appears in both Info and (for historical
compatibility) plain text output.  Pair with @code{@@end ifdocbook}
resp.@: @code{@@end ifhtml}@enddots{}
@xref{Conditionals}.

@code{@@ifxml} is deprecated and will be removed in a future release.

@item @@ifnotdocbook
@itemx @@ifnotepub
@itemx @@ifnothtml
@itemx @@ifnotlatex
@itemx @@ifnotplaintext
@itemx @@ifnottex
@itemx @@ifnotxml
Begin text to be ignored in one output format but not the others.
@code{@@ifnothtml} text is omitted from HTML output, etc.  Pair with
the corresponding @code{@@end ifnot@var{format}}.
@xref{Conditionals}.

@code{@@ifnotxml} is deprecated and will be removed in a future release.

@item @@ifnotinfo
Begin text to appear in output other than Info and (for historical
compatibility) plain text.  Pair with @code{@@end ifnotinfo}.
@xref{Conditionals}.

@item @@ifset @var{txivar}
If the Texinfo variable @var{txivar} is set, format the following
text.  Pair with @code{@@end ifset}.  @xref{@code{@@set @@clear
@@value}}.

@item @@iftex
Begin text to appear only in the @TeX{} output.  Pair with @code{@@end
iftex}.  @xref{Conditionals}.

@item @@ignore
Begin text that will not appear in any output.  Pair with @code{@@end
ignore}.  @xref{Comments, , Comments and Ignored Text}.

@item @@image@{@var{filename}, [@var{width}], [@var{height}], [@var{alt}], [@var{ext}]@}
Include graphics image in external @var{filename} scaled to the given
@var{width} and/or @var{height}, using @var{alt} text and looking for
@samp{@var{filename}.@var{ext}} in HTML@.  @xref{Images}.

@item @@include @var{filename}
Read the contents of Texinfo source file @var{filename}.  @xref{Include Files}.

@item @@indent
Insert paragraph indentation.  @xref{@code{@@indent}}.

@item @@indentedblock
Indent a block of arbitrary text on the left.  Pair with @code{@@end
indentedblock}.  @xref{@code{@@indentedblock}}.

@item @@indicateurl@{@var{indicateurl}@}
Indicate text that is a uniform resource locator for the World Wide
Web.  @xref{@code{@@indicateurl}}.

@item @@inforef@{@var{node-name}, [@var{entry-name}], @var{info-file-name}@}
Make a cross-reference to an Info file for which there is no printed
manual.  @xref{@code{@@inforef}}.

@item @@inlinefmt@{@var{fmt}, @var{text}@}
Insert @var{text} only if the output format is @var{fmt}.
@xref{Inline Conditionals}.

@item @@inlinefmtifelse@{@var{fmt}, @var{text}, @var{else-text}@}
Insert @var{text} if the output format is @var{fmt}, else @var{else-text}.

@item @@inlineifclear@{@var{var}, @var{text}@}
@itemx @@inlineifset@{@var{var}, @var{text}@}
Insert @var{text} only if the Texinfo variable @var{var} is (not) set.

@item @@inlineraw@{@var{fmt}, @var{raw-text}@}
Insert @var{text} as in a raw conditional, only if the output format
is @var{fmt}.

@item \input @var{macro-definitions-file}
Use the specified macro definitions file.  This command is used only
in the first line of a Texinfo file to cause @TeX{} to make use of the
@file{texinfo} macro definitions file.  The @code{\} in @code{\input}
is used instead of an @code{@@} because @TeX{} does not recognize
@code{@@} until after it has read the definitions file.  @xref{Texinfo
File Header}.

@item @@insertcopying
Insert the text previously defined with the @code{@@copying}
environment.  @xref{@code{@@insertcopying}}.

@item @@item
Indicate the beginning of a marked paragraph for @code{@@itemize} and
@code{@@enumerate}; indicate the beginning of the text of a first column
entry for @code{@@table}, @code{@@ftable}, and @code{@@vtable}.
@xref{Lists and Tables}.

@item @@itemize @var{mark-generating-character-or-command}
Begin an unordered list: indented paragraphs with a mark, such as
@code{@@bullet}, inside the left margin at the beginning of each item.
Pair with @code{@@end itemize}.  @xref{@code{@@itemize}}.

@item @@itemx
Like @code{@@item} in @code{@@table}, @code{@@ftable}, and @code{@@vtable},
but do not generate extra vertical space above the
item text.  Thus, when several items have the same description, use
@code{@@item} for the first and @code{@@itemx} for the others.
@xref{@code{@@itemx}}.

@item @@kbd@{@var{keyboard-characters}@}
Indicate characters of input to be typed by users.  @xref{@code{@@kbd}}.

@item @@kbdinputstyle @var{style}
Specify when @code{@@kbd} should use a font distinct from
@code{@@code} according to @var{style}: @code{code}, @code{distinct},
@code{example}.  @xref{@code{@@kbd}}.

@item @@key@{@var{key-name}@}
Indicate the name of a key on a keyboard.  @xref{@code{@@key}}.

@item @@kindex @var{entry}
Add @var{entry} to the index of keys.
@xref{Index Entries, , Defining the Entries of an Index}.

@item @@L@{@}
@itemx @@l@{@}
Generate the uppercase and lowercase Polish suppressed-L letters,
respectively: @L{}, @l{}.

@item @@LaTeX@{@}
Generate the @LaTeX{} logo.  @xref{@code{@@TeX @@LaTeX}}.

@item @@latex
Enter @LaTeX{} completely.  Pair with @code{@@end latex}.  @xref{Raw
Formatter Commands}.

@item @@leq@{@}
Generate a less-than-or-equal sign, `@leq{}'.  @xref{@code{@@geq @@leq}}.

@item @@linemacro @var{macroname} @{@var{params}@}
Define a new macro which takes rest of the line as an argument, and
expands to a whole number of complete lines.  @xref{Line Macros}.

@item @@link@{@var{nodename}, @var{label}, @var{manual-name}@}
Create a plain link with no visible markup or page reference.
@xref{@code{@@link}}.

@item @@lisp
Begin an example of Lisp code.  Indent text, do not fill, and select
fixed-width font.  Pair with @code{@@end lisp}.  @xref{@code{@@lisp}}.

@item @@listoffloats
Produce a table-of-contents-like listing of @code{@@float}s.
@xref{@code{@@listoffloats}}.

@item @@lowersections
Change subsequent chapters to sections, sections to subsections, and so
on. @xref{Raise/lower sections, , @code{@@raisesections} and
@code{@@lowersections}}.

@item @@macro @var{macroname} @{@var{params}@}
Define a new Texinfo command @code{@@@var{macroname}@{@var{params}@}}.
Pair with @code{@@end macro}.  @xref{Defining Macros}.

@item @@maketitle
Generate a title page and possibly also the following page.  @xref{Document
Metadata}.

@item @@majorheading @var{title}
Print an unnumbered chapter-like heading, but omit from the table of
contents.  This generates more vertical whitespace before the heading
than the @code{@@chapheading} command.  @xref{@code{@@majorheading
@@chapheading}}.

@item @@math@{@var{mathematical-expression}@}
Format a mathematical expression.  @xref{Inserting Math}.

@item @@menu
Mark the beginning of a menu of nodes.  No effect in a printed manual.
Pair with @code{@@end menu}.  @xref{Menus}.

@item @@microtype @var{on-off}
Turn microtype on or off.  @xref{Microtypography}.

@item @@minus@{@}
Generate a minus sign, `@minus{}'.  @xref{@code{@@minus}}.

@item @@multitable @var{column-width-spec}
Begin a multi-column table.  Begin each row with @code{@@item} or
@code{@@headitem}, and separate columns with @code{@@tab}.  Pair with
@code{@@end multitable}.  @xref{Multitable Column Widths}.

@item @@namedanchor@{@var{anchor-name}, @var{xref-name}@}
Define a target for a cross-reference.  @xref{@code{@@anchor}}.

@item @@need @var{n}
Start a new page in a printed manual if fewer than @var{n} mils
(thousandths of an inch) remain on the current page.
@xref{@code{@@need}}.

@item @@node @var{name}, [@var{next}], [@var{previous}], [@var{up}]
Begin a new node.  Only the first argument is mandatory.
@xref{Writing a Node}.

@item @@nodedescription @var{node-description}
Provide a short elaboration of the purpose of a node.
@xref{Node Descriptions}.

@item @@nodedescriptionblock
Pair with @samp{@@end nodedescriptionblock}.  Used to start a longer
node description.  @xref{Node Descriptions}.

@item @@noindent
Prevent text from being indented as if it were a new paragraph.
@xref{@code{@@noindent}}.

@item @@novalidate
Suppress validation of node references and omit creation of auxiliary
files with @TeX{}.  Use before any sectioning or cross-reference 
commands.  @xref{Pointer Validation}.

@item @@O@{@}
@itemx @@o@{@}
Generate the uppercase and lowercase O-with-slash letters, respectively:
@O{}, @o{}.

@item  @@oddfooting [@var{left}] @@| [@var{center}] @@| [@var{right}]
@itemx @@oddheading [@var{left}] @@| [@var{center}] @@| [@var{right}]
Specify page footings resp.@: headings for odd-numbered (right-hand)
pages.  @xref{Custom Headings, ,
How to Make Your Own Headings}.

@item @@OE@{@}
@itemx @@oe@{@}
Generate the uppercase and lowercase OE ligatures, respectively:
@OE{}, @oe{}.  @xref{Inserting Accents}.

@item @@ogonek@{@var{c}@}
Generate an ogonek diacritic under the next character, as in
@ogonek{a}.  @xref{Inserting Accents}.

@item @@option@{@var{option-name}@}
Indicate a command-line option, such as @option{-l} or
@option{--help}.  @xref{@code{@@option}}.

@item @@ordf@{@}
@itemx @@ordm@{@}
Generate the feminine and masculine Spanish ordinals, respectively:
@ordf{}, @ordm{}.  @xref{Inserting Accents}.

@item @@page
Start a new page in a printed manual.  @xref{@code{@@page}}.

@item @@pagesizes [@var{width}][, @var{height}]
Change page dimensions.  @xref{pagesizes}.

@item @@paragraphindent @var{indent}
Indent paragraphs by @var{indent} number of spaces (perhaps 0); preserve
source file indentation if @var{indent} is @code{asis}.
@xref{@code{@@paragraphindent}}.

@item @@part @var{title}
Begin a group of chapters or appendixes; included in the tables of
contents.
@xref{@code{@@part}}.

@item @@pindex @var{entry}
Add @var{entry} to the index of programs.  @xref{Index Entries, , Defining
the Entries of an Index}.

@item @@publication
Start information about the publication of the document.  Pair with
@samp{@@end publication}.  @xref{Document Metadata}.

@item @@point@{@}
Indicate the position of point in a buffer to the reader with a glyph:
@samp{@point{}}.  @xref{@code{@@point}}.

@item @@pounds@{@}
Generate the pounds sterling currency sign, @samp{@pounds{}}.
@xref{@code{@@pounds}}.

@item @@print@{@}
Indicate printed output to the reader with a glyph: @samp{@print{}}.
@xref{@code{@@print}}.

@item @@printindex @var{index-name}
Generate the index for @var{index-name}.  @xref{Printing Indices & Menus}.

@item @@pxref@{@var{node}, [@var{entry}], [@var{node-title}], [@var{info-file}], [@var{printed-manual}]@}
Make a reference to be used within parentheses.  Starts with a lowercase
`see' in a printed manual.  The first argument is mandatory, except for
references to whole manuals.  To refer to another manual as a whole,
the @var{printed-manual} and/or the @var{info-file} are the only
required arguments.  @xref{@code{@@pxref}}.

@item @@questiondown@{@}
Generate an upside-down question mark.  @xref{Inserting Accents}.

@item @@quotation
Narrow the margins to indicate text that is quoted from another work.
Takes optional argument specifying prefix text.  Pair with @code{@@end
quotation}.  @xref{@code{@@quotation}}.

@item @@quotedblleft@{@}
@itemx @@quotedblright@{@}
@itemx @@quoteleft@{@}
@itemx @@quoteright@{@}
@itemx @@quotedblbase@{@}
@itemx @@quotesinglbase@{@}
Produce various quotation marks: @quotedblleft{} @quotedblright{}
@quoteleft{} @quoteright{} @quotedblbase{} @quotesinglbase{}.
@xref{Inserting Quotation Marks}.

@item @@r@{@var{text}@}
Set @var{text} in the regular @r{roman} font, if possible.
@xref{Fonts}.

@item @@raggedright
Fill text; left justify every line while leaving the right end ragged.
Leave font as is.  Pair with @code{@@end raggedright}.
@xref{@code{@@raggedright}}.

@item @@raisesections
Change subsequent sections to chapters, subsections to sections, and so
on.  @xref{Raise/lower sections}.

@item @@ref@{@var{node}, [@var{entry}], [@var{node-title}], [@var{info-file}], [@var{printed-manual}]@}
Make a plain reference that does not start with any special text.
Follow command with a punctuation mark.  The first argument is mandatory, except for
references to whole manuals.  To refer to another manual as a whole,
the @var{printed-manual} and/or the @var{info-file} are the only
required arguments.  @xref{@code{@@ref}}.

@item @@registeredsymbol@{@}
Generate the legal symbol @registeredsymbol{}.
@xref{@code{@@registeredsymbol}}.

@item @@result@{@}
Indicate the result of an expression to the reader with a special
glyph: @samp{@result{}}.  @xref{@code{@@result}}.

@item @@ringaccent@{@var{c}@}
Generate a ring accent over the next character, as in @ringaccent{o}.
@xref{Inserting Accents}.

@item @@samp@{@var{text}@}
Indicate a literal example of a sequence of characters, in general.
@xref{@code{@@samp}}.

@item @@sansserif@{@var{text}@}
Set @var{text} in a @sansserif{sans serif} font if possible.
@xref{Fonts}.

@item @@sc@{@var{text}@}
Set @var{text} in a small caps font if possible, and uppercase
in Info.  @xref{Smallcaps}.

@item @@section @var{title}
Begin a section within a chapter.  The section title appears in the
table of contents.  Within @code{@@chapter} and @code{@@appendix}, the section
title is numbered; within @code{@@unnumbered}, the section is unnumbered.
@xref{@code{@@section}}.

@item @@seealso@{@var{index-text}@}
Use in an index entry to refer the reader to another relevant index entry.
@xref{Advanced Indexing}.

@item @@seeentry@{@var{index-text}@}
Use in an index entry to redirect the reader to another index entry.
@xref{Advanced Indexing}.

@item @@set @var{txivar} [@var{string}]
Define the Texinfo variable @var{txivar}, optionally to the value
@var{string}.  @xref{@code{@@set @@clear @@value}}.

@item @@setchapternewpage @var{on-off-odd}
Specify whether chapters start on new pages, and if so, whether on
odd-numbered (right-hand) new pages.  @xref{@code{@@setchapternewpage}}.

@item @@setfilename @var{info-file-name}
Provide a name to be used for the output files.  This command is ignored
for @TeX{} formatting.  @xref{@code{@@setfilename}}.

@item @@settitle @var{title}
Specify the title for page headers in a printed manual, and the
default document title for HTML.
@xref{@code{@@settitle}}.

@item @@shortcaption
Define the short caption for a @code{@@float}.  @xref{@code{@@caption
@@shortcaption}}.

@item @@shortcontents
Print a short table of contents, with chapter-level entries only,
or specify that a short table of contents should be output.
For formats that may output a short table of contents.
@xref{Contents, , Generating a Table of Contents}.

@item @@shorttitlepage @var{title}
Generate a minimal title page.  @xref{Titlepage & Copyright Page}.

@item @@slanted@{@var{text}@}
Set @var{text} in a @slanted{slanted} font if possible.  @xref{Fonts}.

@item @@smallbook
In printed output, use a 7 by 9.25 inch format rather than the
regular 8.5 by 11 inch format.  @xref{@code{@@smallbook}}.

@item @@smalldisplay
Begin a kind of example.  Like @code{@@display}, but use a smaller
font size where possible.  Pair with @code{@@end smalldisplay}.
@xref{small}.

@item @@smallexample
Begin an example.  Like @code{@@example}, but use a smaller font size
where possible.  Pair with @code{@@end smallexample}.
@xref{small}.

@item @@smallformat
Begin a kind of example.  Like @code{@@format}, but use a smaller font
size where possible.  Pair with @code{@@end smallformat}.
@xref{small}.

@item @@smallindentedblock
Like @code{@@indentedblock}, but use a smaller font size where
possible.  Pair with @code{@@end smallindentedblock}.
@xref{small}.

@item @@smalllisp
Begin an example of Lisp code.  Same as @code{@@smallexample}.  Pair
with @code{@@end smalllisp}.  @xref{small}.

@item @@smallquotation
Like @code{@@quotation}, but use a smaller font size where possible.
Pair with @code{@@end smallquotation}.  @xref{small}.

@item @@sortas @{@var{key}@}
Used in the arguments to index commands to give a string by which the 
index entry should be sorted.  @xref{Indexing Commands}.

@item @@sp @var{n}
Skip @var{n} blank lines.  @xref{@code{@@sp}}.

@item @@ss@{@}
Generate the German sharp-S es-zet letter, @ss{}.  @xref{Inserting Accents}.

@item @@strong @{@var{text}@}
Emphasize @var{text} more strongly than @code{@@emph}.
@xref{emph & strong, , Emphasizing Text}.

@item @@sub @{@var{text}@}
Set @var{text} as a subscript.  @xref{Inserting Subscripts and Superscripts}.

@item @@subentry
Use in an index entry to separate parts of a multi-level entry.
@xref{Advanced Indexing}.

@item @@subheading @var{title}
Print an unnumbered subsection-like heading, but omit from the table
of contents of a printed manual.
@xref{@code{@@unnumberedsubsec @@appendixsubsec @@subheading}}.

@item @@subsection @var{title}
Begin a subsection within a section.  The subsection title appears in
the table of contents.
Same context-dependent numbering as @code{@@section}.
@xref{@code{@@subsection}}.

@item @@subsubheading @var{title}
Print an unnumbered subsubsection-like heading, but omit from the
table of contents of a printed manual.  @xref{@code{@@subsubsection}}.

@item @@subsubsection @var{title}
Begin a subsubsection within a subsection.  The subsubsection title
appears in the table of contents.  Same context-dependent numbering as
@code{@@section}.  @xref{@code{@@subsubsection}}.

@item @@subtitle @var{title}
Set a subtitle for the title page.  @xref{@code{@@title @@subtitle @@author}}.

@item @@summarycontents
Print or specify a short table of contents.  Synonym for @code{@@shortcontents}.
@xref{Contents, , Generating a Table of Contents}.

@item @@sup @{@var{text}@}
Set @var{text} as a superscript.  @xref{Inserting Subscripts and Superscripts}.

@item @@syncodeindex @var{from-index} @var{to-index}
Merge the index named in the first argument into the index named in
the second argument, formatting the entries from the first index with
@code{@@code}.  @xref{Combining Indices}.

@item @@synindex @var{from-index} @var{to-index}
Merge the index named in the first argument into the index named in
the second argument.  Do not change the font of @var{from-index}
entries.  @xref{Combining Indices}.

@item @@t@{@var{text}@}
Set @var{text} in a @t{fixed-width}, typewriter-like font, if possible.
@xref{Fonts}.

@item @@tab
Separate columns in a row of a multitable.  @xref{Multitable Rows}.

@item @@table @var{formatting-command}
Begin a two-column table (description list), using @code{@@item} for
each entry.  Write each first column entry on the same line as
@code{@@item}.  First column entries are printed in the font resulting
from @var{formatting-command}.  Pair with @code{@@end table}.
@xref{Two-column Tables, , Making a Two-column Table}.  Also see
@ref{@code{@@ftable @@vtable}}, and @ref{@code{@@itemx}}.

@item @@TeX@{@}
Generate the @TeX{} logo.  @xref{@code{@@TeX @@LaTeX}}.

@item @@tex
Enter @TeX{} completely.  Pair with @code{@@end tex}.  @xref{Raw
Formatter Commands}.

@item @@textdegree@{@}
Generate the degree symbol.  @xref{@code{@@textdegree}}.

@item @@thischapter
@itemx @@thischaptername
@itemx @@thischapternum
@itemx @@thissection
@itemx @@thissectionname
@itemx @@thissectionnum
@itemx @@thispart
@itemx @@thisfile
@itemx @@thispage
@itemx @@thistitle
Only allowed in a heading or footing.  Stands for, respectively, the
number and name of the current chapter (in the format `Chapter 1:
Title'), the current chapter name only, the current chapter number
only, the number and name of the current section, the current section
name only, the current section number only, the current part name, the
file name, the current page number, and the title of the document.
@xref{Custom Headings,, How to Make Your Own Headings}.

@item @@TH@{@}
@itemx @@th@{@}
Generate the uppercase and lowercase Icelandic letter thorn, respectively:
@TH{}, @th{}.  @xref{Inserting Accents}.

@item @@tie@{@}
Generate a normal interword space at which a line break is not
allowed.  @xref{@code{@@tie}}.

@item @@tieaccent@{@var{cc}@}
Generate a tie-after accent over the next two characters @var{cc}, as in
`@tieaccent{oo}'.  @xref{Inserting Accents}.

@item @@tindex @var{entry}
Add @var{entry} to the index of data types.  @xref{Index Entries, ,
Defining the Entries of an Index}.

@item @@title @var{title}
Set the title for the title page.  @xref{@code{@@title @@subtitle @@author}}.

@item @@titlefont@{@var{text}@}
Print @var{text} in a larger than normal font, if possible.
@xref{@code{@@titlefont @@center @@sp}}.

@item @@titlepage
Begin the title page.  Write the command on a line of its own, paired
with @code{@@end titlepage}.  The title page is not output, in the
default case, in online formats.  @xref{@code{@@titlepage}}.

@item @@today@{@}
Insert the current date, in `1 Jan 1900' style.  @xref{Custom
Headings, , How to Make Your Own Headings}.

@item @@top @var{title}
Mark the topmost @code{@@node} in the file, which must be defined on
the line immediately preceding the @code{@@top} command.  The title is
formatted as a chapter-level heading.  In @TeX{} the @code{@@top}
command is merely a synonym for @code{@@unnumbered}.

@item @@U@{@var{hex}@}
Output a representation of Unicode character U+@var{hex}.
@xref{Inserting Unicode}.

@item @@u@{@var{c}@}
@itemx @@ubaraccent@{@var{c}@}
@itemx @@udotaccent@{@var{c}@}
Generate a breve, underbar, or underdot accent, respectively, over or
under the character @var{c}, as in @u{o}, @ubaraccent{o},
@udotaccent{o}.  @xref{Inserting Accents}.

@item @@unmacro @var{macroname}
Undefine the macro @code{@@@var{macroname}} if it has been defined.
@xref{Defining Macros}.

@item @@unnumbered @var{title}
Begin a chapter that appears without chapter numbers of any kind.  The
title appears in the table of contents.  @xref{@code{@@unnumbered @@appendix}}.

@item @@unnumberedsec @var{title}
Begin a section that appears without section numbers of any kind.  The
title appears in the table of contents.  @xref{@code{@@unnumberedsec
@@appendixsec @@heading}}.

@item @@unnumberedsubsec @var{title}
Begin an unnumbered subsection.  The title appears in the table of
contents.  @xref{@code{@@unnumberedsubsec @@appendixsubsec @@subheading}}.

@item @@unnumberedsubsubsec @var{title}
Begin an unnumbered subsubsection.  The title appears in the table of
contents.  @xref{@code{@@subsubsection}}.

@item @@uref@{@var{url}[, @var{displayed-text}][, @var{replacement}@}
@itemx @@url@{@var{url}[, @var{displayed-text}][, @var{replacement}@}
Define a cross-reference to an external uniform resource locator,
e.g., for the World Wide Web.  @xref{@code{@@url}}.

@item @@urefbreakstyle @var{style}
Specify how @code{@@uref}/@code{@@url} should break at special
characters: @code{after}, @code{before}, @code{none}.
@xref{@code{@@url}}.

@item @@v@{@var{c}@}
Generate check accent over the character @var{c}, as in @v{o}.
@xref{Inserting Accents}.

@item @@value@{@var{txivar}@}
Insert the value, if any, of the Texinfo variable @var{txivar},
previously defined by @code{@@set}.  @xref{@code{@@set @@clear
@@value}}.

@item @@var@{@var{metasyntactic-variable}@}
Highlight a metasyntactic variable, which is something that stands for
another piece of text.  @xref{@code{@@var}}.

@item @@verb@{@var{delim} @var{literal} @var{delim}@}
Output @var{literal}, delimited by the single character @var{delim},
exactly as is (in the fixed-width font), including any whitespace or
Texinfo special characters.  @xref{@code{@@verb}}.

@item @@verbatim
Output the text of the environment exactly as is (in the fixed-width
font).  Pair with @code{@@end verbatim}.  @xref{@code{@@verbatim}}.

@item @@verbatiminclude @var{filename}
Output the contents of @var{filename} exactly as is (in the
fixed-width font).  @xref{@code{@@verbatiminclude}}.

@item @@vindex @var{entry}
Add @var{entry} to the index of variables.  @xref{Index Entries, ,
Defining the Entries of an Index}.

@item @@vskip @var{amount}
In a printed manual, insert whitespace so as to push text on the
remainder of the page towards the bottom of the page.  Used in
formatting the copyright page with the argument @samp{0pt plus
1filll}.  (Note spelling of @samp{filll}.)  @xref{Copyright}.

@item @@vtable @var{formatting-command}
Begin a two-column table, using @code{@@item} for each entry.
Automatically enter each of the items in the first column into the
index of variables.  Pair with @code{@@end vtable}.  The same as
@code{@@table}, except for indexing.  @xref{@code{@@ftable @@vtable}}.

@item @@w@{@var{text}@}
Disallow line breaks within @var{text}.  @xref{@code{@@w}}.

@item @@xml
Deprecated, will be removed in a future release.  Text will not
appear in any output.  Pair with @code{@@end xml}.  @xref{Raw
Formatter Commands}.

@item @@xref@{@var{node}, [@var{entry}], [@var{node-title}], [@var{info-file}], [@var{printed-manual}]@}
Make a reference that starts with `See' in a printed manual.  Follow
command with a punctuation mark.  The first argument is mandatory, except for
references to whole manuals.  To refer to another manual as a whole,
the @var{printed-manual} and/or the @var{info-file} are the only
required arguments.  @xref{@code{@@xref}}.

@item @@xrefautomaticsectiontitle @var{on-off}
By default, use the section title instead of the node name in cross
references, including in node headers in HTML.  @xref{Three Arguments}.

@item @@xrefname @var{xref-name}
Use immediately after a @code{@@node} line to provide text for linking
to that node when @code{xrefautomaticsectiontitle} is on, without
printing a heading.  @xref{Unstructured Nodes}.

@end table


@node Command Contexts
@section @@-Command Contexts

@cindex Contexts, of @@-commands

Here we describe approximately which @@-commands can be used in which
contexts.  It is not exhaustive or meant to be a complete reference.
Discrepancies between the information here and the Texinfo processors
implementations are most likely to be resolved in favor of the
implementations.

By @dfn{general text} below, we mean anything except sectioning and
other such outer-level document commands, such as @code{@@section},
@code{@@node}, and @code{@@setfilename}.

@code{@@c}, @code{@@comment} and @code{@@if ... @@end if} conditional
commands may appear anywhere (except the conditionals must still be on lines by
themselves).  @code{@@caption} and @code{@@shortcaption} may only appear in
@code{@@float} but may contain general text.  @code{@@footnote} content
likewise.

@@-commands with braces marking text (such as @code{@@strong},
@code{@@sc}, @code{@@asis}) may contain raw formatter commands such as
@code{@@html} but no other block commands (other commands terminated
by @code{@@end}) and may not be split across paragraphs, but may
otherwise contain general text.

In addition to the block command restriction, on @code{@@center},
@code{@@exdent} and @code{@@item} in @code{@@table} lines, @@-commands
that makes only sense in a paragraph are not accepted, such as
@code{@@indent}.

In addition to the above, sectioning commands cannot contain
@code{@@anchor}, @code{@@footnote} or @code{@@verb}.

In addition to the above, remaining commands (@code{@@node},
@code{@@anchor}, @code{@@printindex}, @code{@@ref}, @code{@@math},
@code{@@cindex}, @code{@@url}, @code{@@image}, and so on) cannot
contain cross-reference commands (@code{@@ref}, @code{@@xref},
@code{@@pxref} and @code{@@inforef}).

For precise and complete information, we suggest looking into the
test suite in the sources, which exhaustively tries combinations.


@node Obsolete @@-Commands
@section Obsolete @@-Commands

Here are Texinfo @@-commands which are obsolete or have been removed 
completely.  This section is for historical purposes.

@ftable @code
@item @@refill
This command used to refill and indent the paragraph after all the
other processing has been done.  It is no longer needed, since all
formatters now automatically refill as needed, but you may still see
it in the source to some manuals, as it does no harm.

@cindex Contents, after title page
@cindex Table of contents, after title page
@item @@setcontentsaftertitlepage
In the past, the contents commands were sometimes placed at the end of
the file, after any indices and just before the @code{@@bye}, but we
no longer recommend this.
This command could be used by a user printing a manual, to force the 
contents to be printed after the title page
(after the @samp{@@end titlepage} line)
even if the @code{@@contents} command was at the end of the manual.

@item @@setshortcontentsaftertitlepage
This placed the short table of contents after the @samp{@@end titlepage}
command even if the @code{@@shortcontents} command was at the end.

@item @@clickstyle @@@var{cmd}
This could be used to give a command to be used for @code{@@click}.
For example, @code{@@clickstyle @@result} had the same effect as
@code{@@alias click=result}.  The command was not very useful and
does not appear to ever have been used by anyone.

@end ftable


@node Tips
@nodedescription Hints on how to write a Texinfo document.
@appendix Tips and Hints

Writers of GNU manuals should consult @ref{GNU Manuals,,, standards,
GNU Coding Standards}.  Here are some other tips for writing Texinfo
documentation:

@cindex Tips
@cindex Usage tips
@cindex Hints
@itemize @bullet
@item
Write in the present tense, not in the past or the future.

@item
Write actively!  For example, write ``We recommend that @dots{}'' rather
than ``It is recommended that @dots{}''.

@item
Design your manual so that it can be read sequentially, as far as
possible.  People tire of flipping back and forth to find information
that should be presented to them as they need it.

@item
Use 70 or 72 as your fill column.  Longer lines are hard to read.

@item
Include a copyright notice and copying permissions.

@end itemize


@subsubheading Index, Index, Index!

@itemize @bullet
@item
Write many index entries, in different ways.  You can write index entries
as you write the body of the text, or write them afterwards.

@item
Write index entries only where a topic is discussed significantly.  For
example, it is not useful to index ``debugging information'' in a
chapter on reporting bugs.  Someone who wants to know about debugging
information will certainly not find it in that chapter.

@item
Write the indexing commands that refer to a whole section immediately
after the section command.  Write the indexing commands that refer to
a paragraph before that paragraph; this way, an index entry points to
the first page of a paragraph that is split across pages.

In the example that follows, a blank line comes after the index
entry for ``Leaping'':

@example
@group
@@section The Dog and the Fox
@@cindex Jumping, in general
@@cindex Leaping

@@cindex Dog, lazy, jumped over
@@cindex Lazy dog jumped over
@@cindex Fox, jumps over dog
@@cindex Quick fox jumps over dog
The quick brown fox jumps over the lazy dog.
@end group
@end example

@noindent
(Note that the example shows entries for the same concept that are
written in different ways---@samp{Lazy dog}, and @samp{Dog, lazy}---so
readers can look up the concept in different ways.)

@item
Consistently capitalize the first word of every concept index entry,
or else consistently use lowercase.  Terse entries often call for
lowercase; longer entries for capitalization.  Whichever case
convention you use, please use one or the other consistently!  Mixing
the two styles looks bad.

@item
Always capitalize or use uppercase for those words in an index for
which this is proper, such as names of countries or acronyms.  Always
use the appropriate case for case-sensitive names, such as those in C or
Lisp.

@end itemize


@subsubheading Complete Phrases

Complete phrases are easier to read than @dots{}

@itemize @bullet
@item
Write entries in an itemized list as complete sentences; or at least, as
complete phrases.  Incomplete expressions @dots{} awkward @dots{} like
this.

@item
Write the prefatory sentence or phrase for a multi-item list or table as
a complete expression.  Do not write ``You can set:''; instead, write
``You can set these variables:''.  The former expression sounds cut off.
@end itemize


@subsubheading Introducing New Terms

@itemize @bullet
@item
Introduce new terms so that a reader who does not know them can
understand them from context; or write a definition for the term.

For example, in the following, the terms ``check in'', ``register'' and
``delta'' are all appearing for the first time; the example sentence should be
rewritten so they are understandable.

@quotation
The major function assists you in checking in a file to your
version control system and registering successive sets of changes to
it as deltas.
@end quotation

@item
Use the @code{@@dfn} command around a word being introduced, to indicate
that the reader should not expect to know the meaning already, and
should expect to learn the meaning from this passage.
@end itemize


@subsubheading Bad Examples

Here are a few examples of bad writing to avoid:

@quotation
When you are done editing the file, you must perform a
@t{@@dfn}@{check in@}.
@end quotation

@noindent
In this example, say, `` @dots{} you must @t{@@dfn}@{check
in@} the new version.''  That flows better.

@quotation
SCCS, RCS and other version-control systems all perform similar
functions in broadly similar ways (it is this resemblance which makes
a unified control mode like this possible).
@end quotation

@noindent
In this example, say, ``@dots{} makes a unified interface such as VC
mode possible.''


@subsubheading Periods Outside of Quotes

Place periods and other punctuation marks @emph{outside} of quotations,
unless the punctuation is part of the quotation.  This practice goes
against some publishing conventions in the United States, but enables the
reader to distinguish between the contents of the quotation and the
whole passage.

For example, you should write the following sentence with the period
outside the end quotation marks:

@example
Evidently, @samp{au} is an abbreviation for ``author''.
@end example

@noindent
since @samp{au} does @emph{not} serve as an  abbreviation for
@samp{author.} (with a period following the word).


@subsubheading Blank Lines

@itemize @bullet
@item
Insert a blank line between a sectioning command and the first following
sentence or paragraph, or between the indexing commands associated with
the sectioning command and the first following sentence or paragraph, as
shown in the tip on indexing.  It makes the source easier to read.

@item
Always insert a blank line before a @code{@@table} command and after an
@code{@@end table} command; but never insert a blank line after an
@code{@@table} command.

@need 1000
For example,

@example
@group
Types of fox:

@@table @@samp
@@item Quick
Jump over lazy dogs.
@end group

@group
@@item Brown
Also jump over lazy dogs.
@@end table

@end group
@group
@@noindent
On the other hand, @dots{}
@end group
@end example

Insert blank lines before and after @code{@@itemize} @dots{} @code{@@end
itemize} and @code{@@enumerate} @dots{} @code{@@end enumerate} in the
same way.
@end itemize


@subsubheading Spaces

Do not use spaces to format a Texinfo file, except inside of
@code{@@example} @dots{} @code{@@end example} and other literal
environments and commands.

@need 700
For example, @TeX{} fills the following:

@example
@group
   @@kbd@{C-x v@}
   @@kbd@{M-x vc-next-action@}
      Perform the next logical operation
      on the version-controlled file
      corresponding to the current buffer.
@end group
@end example

@need 950
@noindent
so it looks like this:

@iftex
@quotation
   @kbd{C-x v}
   @kbd{M-x vc-next-action}
      Perform the next logical operation on the version-controlled file
      corresponding to the current buffer.
@end quotation
@end iftex
@ifnottex
@quotation
`C-x v' `M-x vc-next-action' Perform the next logical operation on the
version-controlled file corresponding to the current buffer.
@end quotation
@end ifnottex

@noindent
In this case, the text should be formatted with
@code{@@table}, @code{@@item}, and @code{@@itemx}, to create a table.


@subsubheading @@code, @@samp, @@var, and @samp{---}

@itemize @bullet
@item
Use @code{@@code} around Lisp symbols, including command names.
For example,

@example
The main function is @@code@{vc-next-action@}, @dots{}
@end example

@item
Avoid putting letters such as @samp{s} immediately after a
@samp{@@code} command.  Such letters look bad.

@item
Use @code{@@var} around meta-variables.  Do not write angle brackets
around them.

@item
Use three hyphens in a row, @samp{---}, to indicate a long dash.
The Info formatter reduces three hyphens to two; a long dash is
typeset in other output formats.
@end itemize


@subsubheading Program Invocation Nodes

You can invoke programs such as Emacs, GCC, and @code{gawk} from a
shell.  The documentation for each program should contain a section that
describes this.  Unfortunately, if the node names and titles for these
sections are all different, they are difficult for users to find.

So, there is a convention to name such sections with a phrase beginning
with the word `Invoking', as in `Invoking Emacs'; this way, users can
find the section easily.


@subsubheading C functions

When you use @code{@@example} to describe a C function's calling
conventions, use the ANSI C syntax, like this:

@example
void dld_init (char *@@var@{path@});
@end example

@noindent
And in the subsequent discussion, refer to the argument values by
writing the same argument names, again highlighted with
@code{@@var}.

Also, it is best to avoid writing @code{#include} above the
declaration just to indicate that the function is declared in a
header file.  The practice may give the misimpression that the
@code{#include} belongs near the declaration of the function.  Either
state explicitly which header file holds the declaration or, better
yet, name the header file used for a group of functions at the
beginning of the section that describes the functions.

@anchor{texi-elements-by-size}
@subsubheading Node Length

Keep nodes (sections) to a reasonable length, whatever reasonable
might be in the given context.  Don't hesitate to break up long nodes
into subnodes and have an extensive tree structure; that's what it's
there for.  Many times, readers will probably try to find a single
specific point in the manual, using search, indexing, or just plain
guessing, rather than reading the whole thing from beginning to end.

You can use the @command{texi-elements-by-size} utility to see a list
of all nodes (or sections) in the document, sorted by size (either
lines or words), to find candidates for splitting.  It's in the
@file{util/} subdirectory of the Texinfo sources.


@subsubheading Capitalization

@itemize @bullet
@item
Capitalize ``Texinfo''; it is a name.  Do not write the @samp{x} or
@samp{i} in uppercase.

@item
Capitalize ``Info''; it is a name.

@item
Write @TeX{} using the @code{@@TeX@{@}} command.  Note the uppercase
@samp{T} and @samp{X}.  This command causes the formatters to
typeset the name according to the wishes of Donald Knuth, who wrote
@TeX{}.  (Likewise @code{@@LaTeX@{@}} for @LaTeX{}.)
@end itemize


@subsubheading And Finally @dots{}

@itemize @bullet
@item
Write notes for yourself at the very end of a Texinfo file after the
@code{@@bye}.  None of the processors process text after the
@code{@@bye}; it is as if the text were within @code{@@ignore} @dots{}
@code{@@end ignore}.
@end itemize


@node Sample Texinfo Files
@nodedescription Complete examples, including full texts.
@appendix Sample Texinfo Files
@cindex Sample Texinfo files

This appendix includes texts to be used in GNU manuals.


@node GNU Sample Texts
@section GNU Sample Texts

@cindex GNU sample texts
@cindex Sample texts, GNU
@cindex Full texts, GNU

Following is a sample Texinfo document with the full texts that should
be used (adapted as necessary) in GNU manuals.

As well as the legal texts, it also serves as a practical example of how
many elements in a GNU system can affect the manual.  If you're not
familiar with all these different elements, don't worry.  They're not
required and a perfectly good manual can be written without them.
They're included here nonetheless because many manuals do (or could)
benefit from them.

@xref{Short Sample}, for a minimal example of a Texinfo file.

Here are some notes on the example:

@itemize @bullet
@item
@pindex automake@r{, and version info}
@vindex UPDATED @r{Automake variable}
@vindex UPDATED-MONTH @r{Automake variable}
@vindex VERSION @r{Automake variable}
@pindex time-stamp.el
The @file{version.texi} in the @code{@@include} command is maintained
automatically by Automake (@pxref{Texinfo,,, automake, GNU Automake}).
It sets the @samp{VERSION}, @samp{UPDATED} and @samp{UPDATED-MONTH} 
values used elsewhere.  If your distribution doesn't use Automake, but
you do use Emacs, you may find the @code{time-stamp.el} package helpful
(@pxref{Time Stamps,,, emacs, The GNU Emacs Manual}).

@item
The @code{@@syncodeindex} command reflects the recommendation to use
only one index where possible, to make it easier for readers to look up
index entries.

@item
The @code{@@dircategory} specify a category for the manual.  It is
used for constructing the Info directory.  @xref{Directory Category},
which includes a variety of recommended category names.
@xref{Installing Dir Entries}.

@item
The `Invoking' node is a GNU standard to help users find the basic
information about command-line usage of a given program.  @xref{Manual
Structure Details,,, standards, GNU Coding Standards}.

@item
@cindex GNU Free Documentation License, including entire
@cindex Free Documentation License, including entire
This sample shows how to includes the FDL in a manual using the 
@command{@@include} command.  The @file{fdl.texi} file
is available in the Texinfo and other GNU source distributions.  It is
also available on the GNU website (at 
@uref{https://www.gnu.org/licenses/fdl-1.3.html}) along with guidance 
for using it.

@item
If the FSF is not the copyright holder, then use the appropriate name.

@item
For documents that express your personal views, feelings or
experiences, it is more appropriate to use a license permitting only
verbatim copying, rather than the FDL@.  @xref{Verbatim Copying
License}.

@end itemize

Here is the sample document:

@verbatim
\input texinfo   @c -*-texinfo-*-
@include version.texi
@settitle GNU Sample @value{VERSION}
@syncodeindex pg cp
@copying
This manual is for GNU Sample (version @value{VERSION}, @value{UPDATED}),
which is an example in the Texinfo documentation.

Copyright @copyright{} 2026 Free Software Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts.  A copy of the license is included in the section entitled
``GNU Free Documentation License''.
@end quotation
@end copying

@dircategory Texinfo documentation system
@direntry
* sample: (sample)Invoking sample.
@end direntry

@documentinfo
@title GNU Sample
@subtitle for version @value{VERSION}, @value{UPDATED}
@author A.U. Thor (@email{bug-sample@@gnu.org})
@end documentinfo
@maketitle

@contents

@node Top
@top GNU Sample

This manual is for GNU Sample (version @value{VERSION}, @value{UPDATED}).

@node Invoking sample
@chapter Invoking sample

@pindex sample
@cindex invoking @command{sample}

This is a sample manual.  There is no sample program to
invoke, but if there were, you could see its basic usage
and command line options here.

@node GNU Free Documentation License
@appendix GNU Free Documentation License

@include fdl.texi

@node Index
@unnumbered Index

@printindex cp

@bye
@end verbatim


@node Verbatim Copying License
@section Verbatim Copying License

@cindex Verbatim copying license
@cindex License for verbatim copying

For software manuals and other documentation, it is critical to use a
license permitting free redistribution and updating, so that when a free
program is changed, the documentation can be updated as well.

On the other hand, for documents that express your personal views,
feelings or experiences, it is more appropriate to use a license
permitting only verbatim copying.

Here is a sample text for such a license permitting verbatim copying only.
This is just the license text itself.  For a complete sample document,
see the previous sections.

@verbatim
@copying
This document is a sample for allowing verbatim copying only.

Copyright @copyright{} 2026 Free Software Foundation, Inc.

@quotation
Permission is granted to make and distribute verbatim copies
of this entire document without royalty provided the
copyright notice and this permission notice are preserved.
@end quotation
@end copying
@end verbatim


@node All-permissive Copying License
@section All-permissive Copying License

@cindex All-permissive copying license
@cindex License for all-permissive copying

For software manuals and other documentation, it is important to use a
license permitting free redistribution and updating, so that when a free
program is changed, the documentation can be updated as well.

On the other hand, for small supporting files, short manuals (under 300
lines long) and rough documentation (README files, INSTALL files, etc.),
the full FDL would be overkill.  They can use a simple all-permissive
license.

Here is a sample text for such an all-permissive license.  This is just
the license text itself.  For a complete sample document, see the
previous sections.

@example
Copyright @@copyright@{@} 2026 Free Software Foundation, Inc.

Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.
@end example


@node Texinfo Mode
@nodedescription Using the GNU Emacs Texinfo mode.
@appendix Using Texinfo Mode
@cindex Texinfo mode
@cindex Mode, using Texinfo
@cindex GNU Emacs
@cindex Emacs

You may edit a Texinfo file with any text editor you choose.  A Texinfo
file is no different from any other ASCII file.  However, GNU Emacs
comes with a special mode, called Texinfo mode, that provides Emacs
commands and tools to help ease your work.


@node Texinfo Mode Overview
@nodedescription How Texinfo mode can help you.
@section Texinfo Mode Overview

Texinfo mode provides special features for working with Texinfo files.
You can:

@itemize @bullet
@item
Insert frequently used @@-commands.

@item
Automatically create @code{@@node} lines.

@item
Show the structure of a Texinfo source file.

@item
Automatically create or update the `Next',
`Previous', and `Up' pointers of a node.

@item
Automatically create or update menus.

@item
Automatically create a master menu.

@item
Format a part or all of a file for Info.

@item
Typeset and print part or all of a file.
@end itemize

Perhaps the two most helpful features are those for inserting frequently
used @@-commands and for creating node pointers and menus.


@node Emacs Editing
@nodedescription Texinfo mode adds to GNU Emacs' general purpose editing features.
@section The Usual GNU Emacs Editing Commands

In most cases, the usual Text mode commands work the same in Texinfo
mode as they do in Text mode.  Texinfo mode adds new editing commands
and tools to GNU Emacs' general purpose editing features.  The major
difference concerns filling.  In Texinfo mode, the paragraph
separation variable and syntax table are redefined so that Texinfo
commands that should be on lines of their own are not inadvertently
included in paragraphs.  Thus, the @kbd{M-q} (@code{fill-paragraph})
command will refill a paragraph but not mix an indexing command on a
line adjacent to it into the paragraph.

In addition, Texinfo mode sets the @code{page-delimiter} variable to
the value of @code{texinfo-chapter-level-regexp}; by default, this is
a regular expression matching the commands for chapters and their
equivalents, such as appendices.  With this value for the page
delimiter, you can jump from chapter title to chapter title with the
@kbd{C-x ]} (@code{forward-page}) and @kbd{C-x [}
(@code{backward-page}) commands and narrow to a chapter with the
@kbd{C-x n p} (@code{narrow-to-page}) command.  (@xref{Pages, , ,emacs,
The GNU Emacs Manual}, for details about the page commands.)

GNU Emacs automatically enters Texinfo mode when you visit a
file with a @file{.texinfo}, @file{.texi} or @file{.txi}
extension.  Also, Emacs switches to Texinfo mode
when you visit a
file that has @samp{-*-texinfo-*-} in its first line.  If ever you are
in another mode and wish to switch to Texinfo mode, type @code{M-x
texinfo-mode}.

Like all other Emacs features, you can customize or enhance Texinfo
mode as you wish.  In particular, the keybindings are very easy to
change.  The keybindings described here are the default or standard
ones.


@node Inserting
@nodedescription How to insert frequently used @@-commands.
@section Inserting Frequently Used Commands
@cindex Inserting frequently used commands
@cindex Frequently used commands, inserting
@cindex Commands, inserting them

Texinfo mode provides commands to insert various frequently used
@@-commands into the buffer.  You can use these commands to save
keystrokes.

The insert commands are invoked by typing @kbd{C-c} twice and then the
first letter of the @@-command:

@table @kbd
@findex texinfo-insert-@@code
@item  C-c C-c c
@itemx M-x texinfo-insert-@@code
Insert @code{@@code@{@}} and put the
cursor between the braces.

@findex texinfo-insert-@@dfn
@item  C-c C-c d
@itemx M-x texinfo-insert-@@dfn
Insert @code{@@dfn@{@}} and put the
cursor between the braces.

@findex texinfo-insert-@@end
@item  C-c C-c e
@itemx M-x texinfo-insert-@@end
Insert @code{@@end} and attempt to insert the correct following word,
such as @samp{example} or @samp{table}.  (This command does not handle
nested lists correctly, but inserts the word appropriate to the
immediately preceding list.)

@findex texinfo-insert-@@item
@item  C-c C-c i
@itemx M-x texinfo-insert-@@item
Insert @code{@@item} and put the
cursor at the beginning of the next line.

@findex texinfo-insert-@@kbd
@item  C-c C-c k
@itemx M-x texinfo-insert-@@kbd
Insert @code{@@kbd@{@}} and put the
cursor between the braces.

@findex texinfo-insert-@@node
@item  C-c C-c n
@itemx M-x texinfo-insert-@@node
Insert @code{@@node} and a comment line
listing the sequence for the `Next',
`Previous', and `Up' nodes.
Leave point after the @code{@@node}.

@findex texinfo-insert-@@noindent
@item  C-c C-c o
@itemx M-x texinfo-insert-@@noindent
Insert @code{@@noindent} and put the
cursor at the beginning of the next line.

@findex texinfo-insert-dwim-@@ref
@item  C-c C-c r
@itemx M-x texinfo-insert-dwim-@@ref
This function and binding were added in Emacs 27.1.
Inserts one of @code{@@pxref@{@}}, @code{@@xref@{@}}, or
@code{@@ref@{@}} based on the text around point; calling it near an
unclosed preceding open parenthesis results in @code{@@pxref@{@}}, at
the beginning of a sentence or at @code{(point-min)} yields
@code{@@xref@{@}}, any other location (including inside a word), will
result in @code{@@ref@{@}}.  A numeric argument says how many words
the braces should surround.  Puts the cursor between the braces.

@findex texinfo-insert-@@samp
@item  C-c C-c s
@itemx M-x texinfo-insert-@@samp
Insert @code{@@samp@{@}} and put the
cursor between the braces.

@findex texinfo-insert-@@table
@item  C-c C-c t
@itemx M-x texinfo-insert-@@table
Insert @code{@@table} followed by a @key{SPC}
and leave the cursor after the @key{SPC}.

@findex texinfo-insert-@@var
@item  C-c C-c v
@itemx M-x texinfo-insert-@@var
Insert @code{@@var@{@}} and put the
cursor between the braces.

@findex texinfo-insert-@@example
@item  C-c C-c x
@itemx M-x texinfo-insert-@@example
Insert @code{@@example} and put the
cursor at the beginning of the next line.

@c M-@{  was the binding for texinfo-insert-braces;
@c in Emacs 19, backward-paragraph will take this binding.
@findex texinfo-insert-braces
@item C-c C-c @{
@itemx M-x texinfo-insert-braces
Insert @code{@{@}} and put the cursor between the braces.

@findex up-list
@item C-c @}
@itemx C-c  ]
@itemx M-x up-list
Move from between a pair of braces forward past the closing brace.
Typing @kbd{C-c ]} is easier than typing @kbd{C-c @}}, which
is, however, more mnemonic; hence the two keybindings.  (Also, you can
move out from between braces by typing @kbd{C-f}.)
@end table

To put a command such as @w{@code{@@code@{@dots{}@}}} around an
@emph{existing} word, position the cursor in front of the word and type
@kbd{C-u 1 C-c C-c c}.  This makes it easy to edit existing plain text.
The value of the prefix argument tells Emacs how many words following
point to include between braces---@samp{1} for one word, @samp{2} for
two words, and so on.  Use a negative argument to enclose the previous
word or words.  If you do not specify a prefix argument, Emacs inserts
the @@-command string and positions the cursor between the braces.  This
feature works only for those @@-commands that operate on a word or words
within one line, such as @code{@@kbd} and @code{@@var}.

This set of insert commands was created after analyzing the frequency
with which different @@-commands are used in the @cite{GNU Emacs
Manual} and the @cite{GDB Manual}.  If you wish to add your own insert
commands, you can bind a keyboard macro to a key, use abbreviations,
or extend the code in @file{texinfo.el}.

@findex texinfo-start-menu-description
@cindex Menu description, start
@cindex Description for menu, start
@kbd{C-c C-c C-d} (@code{texinfo-start-menu-description}) is an insert
command that works differently from the other insert commands.  It
inserts a node's section or chapter title in the space for the
description in a menu entry line.  (A menu entry has three parts, the
entry name, the node name, and the description.  Only the node name is
required, but a description helps explain what the node is about.
@xref{Menu Parts, , The Parts of a Menu}.)

To use @code{texinfo-start-menu-description}, position point in a menu
entry line and type @kbd{C-c C-c C-d}.  The command looks for and copies
the title that goes with the node name, and inserts the title as a
description; it positions point at the beginning of the inserted text so you
can edit it.  The function does not insert the title if the menu entry
line already contains a description.

This command is only an aid to writing descriptions; it does not do the
whole job.  You must edit the inserted text since a title tends to use
the same words as a node name but a useful description uses different
words.


@node Showing the Structure
@nodedescription How to show the structure of a file.
@section Showing the Sectioning Structure of a File
@cindex Showing the sectioning structure of a file
@cindex Sectioning structure of a file, showing
@cindex Structure of a file, showing
@cindex Outline of file structure, showing
@cindex Contents-like outline of file structure
@cindex File sectioning structure, showing
@cindex Texinfo file sectioning structure, showing

You can show the sectioning structure of a Texinfo file by using the
@kbd{C-c C-s} command (@code{texinfo-show-structure}).  This command
lists the lines that begin with the @@-commands for @code{@@chapter},
@code{@@section}, and the like.  It constructs what amounts to a table
of contents.  These lines are displayed in another buffer called the
@samp{*Occur*} buffer.  In that buffer, you can position the cursor
over one of the lines and use the @kbd{C-c C-c} command
(@code{occur-mode-goto-occurrence}), to jump to the corresponding spot
in the Texinfo file.

@table @kbd
@findex texinfo-show-structure
@item  C-c C-s
@itemx M-x texinfo-show-structure
Show the @code{@@chapter}, @code{@@section}, and such lines of a
Texinfo file.

@findex occur-mode-goto-occurrence
@item  C-c C-c
@itemx M-x occur-mode-goto-occurrence
Go to the line in the Texinfo file corresponding to the line under the
cursor in the @file{*Occur*} buffer.
@end table

If you call @code{texinfo-show-structure} with a prefix argument by
typing @w{@kbd{C-u C-c C-s}}, it will list not only those lines with the
@@-commands for @code{@@chapter}, @code{@@section}, and the like, but
also the @code{@@node} lines.  You can use @code{texinfo-show-structure}
with a prefix argument to check whether the `Next', `Previous', and `Up'
pointers of an @code{@@node} line are correct.

Often, when you are working on a manual, you will be interested only
in the structure of the current chapter.  In this case, you can mark
off the region of the buffer that you are interested in by using the
@kbd{C-x n n} (@code{narrow-to-region}) command and
@code{texinfo-show-structure} will work on only that region.  To see
the whole buffer again, use @w{@kbd{C-x n w}} (@code{widen}).
(@xref{Narrowing, , , emacs, The GNU Emacs Manual}, for more
information about the narrowing commands.)

@vindex page-delimiter
@cindex Page delimiter in Texinfo mode
In addition to providing the @code{texinfo-show-structure} command,
Texinfo mode sets the value of the page delimiter variable to match
the chapter-level @@-commands.  This enables you to use the @kbd{C-x
]} (@code{forward-page}) and @kbd{C-x [} (@code{backward-page})
commands to move forward and backward by chapter, and to use the
@kbd{C-x n p} (@code{narrow-to-page}) command to narrow to a chapter.
@xref{Pages, , , emacs, The GNU Emacs Manual}, for more information
about the page commands.


@node Using @code{texinfo-show-structure}
@nodedescription How to use @code{texinfo-show-structure}.
@subsection Using @code{texinfo-show-structure}

@cindex Showing the structure of a file

It is not always easy to keep track of the nodes, chapters, sections, and
subsections of a Texinfo file.  This is especially true if you are revising
or adding to a Texinfo file that someone else has written.

In GNU Emacs, in Texinfo mode, the @code{texinfo-show-structure}
command lists all the lines that begin with the @@-commands that
specify the structure: @code{@@chapter}, @code{@@section},
@code{@@appendix}, and so on.  With an argument (@w{@kbd{C-u}}
as prefix argument, if interactive),
the command also shows the @code{@@node} lines.  The
@code{texinfo-show-structure} command is bound to @kbd{C-c C-s} in
Texinfo mode, by default.

The lines are displayed in a buffer called the @samp{*Occur*} buffer,
indented by hierarchical level.  For example, here is a part of what was
produced by running @code{texinfo-show-structure} on this manual:

@example
@group
Lines matching "^@@\\(chapter \\|sect\\|subs\\|subh\\|
unnum\\|major\\|chapheading \\|heading \\|appendix\\)"
in buffer texinfo.texi.
@dots{}
4177:@@chapter Nodes
4198:    @@heading Two Paths
4231:    @@section Node and Menu Illustration
4337:    @@section The @@code@{@@@@node@} Command
4393:        @@subheading Choosing Node and Pointer Names
4417:        @@subsection How to Write a @@code@{@@@@node@} Line
4469:        @@subsection @@code@{@@@@node@} Line Tips
@dots{}
@end group
@end example

This says that lines 4337, 4393, and 4417 of @file{texinfo.texi} begin
with the @code{@@section}, @code{@@subheading}, and @code{@@subsection}
commands respectively.  If you move your cursor into the @samp{*Occur*}
window, you can position the cursor over one of the lines and use the
@kbd{C-c C-c} command (@code{occur-mode-goto-occurrence}), to jump to
the corresponding spot in the Texinfo file.  @xref{Other Repeating
Search, , Using Occur, emacs, The GNU Emacs Manual}, for more
information about @code{occur-mode-goto-occurrence}.

The first line in the @samp{*Occur*} window describes the @dfn{regular
expression} specified by @var{texinfo-heading-pattern}.  This regular
expression is the pattern that @code{texinfo-show-structure} looks for.
@xref{Regexps, , Using Regular Expressions, emacs, The GNU Emacs Manual},
for more information.

When you invoke the @code{texinfo-show-structure} command, Emacs will
display the structure of the whole buffer.  If you want to see the
structure of just a part of the buffer, of one chapter, for example,
use the @kbd{C-x n n} (@code{narrow-to-region}) command to mark the
region.  (@xref{Narrowing, , , emacs, The GNU Emacs Manual}.)  This is
how the example used above was generated.  (To see the whole buffer
again, use @kbd{C-x n w} (@code{widen}).)

If you call @code{texinfo-show-structure} with a prefix argument by
typing @w{@kbd{C-u C-c C-s}}, it will list lines beginning with
@code{@@node} as well as the lines beginning with the @@-sign commands
for @code{@@chapter}, @code{@@section}, and the like.

You can remind yourself of the structure of a Texinfo file by looking at
the list in the @samp{*Occur*} window; and if you have mis-named a node
or left out a section, you can correct the mistake.


@node Using @code{occur}
@nodedescription How to list all lines containing a pattern.
@subsection Using @code{occur}

@cindex Occurrences, listing with @code{@@occur}
@findex occur

Sometimes the @code{texinfo-show-structure} command produces too much
information.  Perhaps you want to remind yourself of the overall structure
of a Texinfo file, and are overwhelmed by the detailed list produced by
@code{texinfo-show-structure}.  In this case, you can use the @code{occur}
command directly.  To do this, type:

@example
@kbd{M-x occur}
@end example

@noindent
and then, when prompted, type a @dfn{regexp}, a regular expression for
the pattern you want to match.  (@xref{Regexps, , Regular Expressions,
emacs, The GNU Emacs Manual}.)  The @code{occur} command works from
the current location of the cursor in the buffer to the end of the
buffer.  If you want to run @code{occur} on the whole buffer, place
the cursor at the beginning of the buffer.

For example, to see all the lines that contain the word
@samp{@@chapter} in them, just type @samp{@@chapter}.  This will
produce a list of the chapters.  It will also list all the sentences
with @samp{@@chapter} in the middle of the line.

If you want to see only those lines that start with the word
@samp{@@chapter}, type @samp{^@@chapter} when prompted by
@code{occur}.  If you want to see all the lines that end with a word
or phrase, end the last word with a @samp{$}; for example,
@samp{catching mistakes$}.  This can be helpful when you want to see
all the nodes that are part of the same chapter or section and
therefore have the same `Up' pointer.

@xref{Other Repeating Search, , Using Occur, emacs , The GNU Emacs Manual},
for more information.


@node Updating Nodes and Menus
@nodedescription How to update or create new nodes and menus.
@section Updating Nodes and Menus

@cindex Updating nodes and menus
@cindex Create nodes, menus automatically
@cindex Insert nodes, menus automatically
@cindex Automatically insert nodes, menus

The @command{texi2any} command will create an Info file for a hierarchically
organized Texinfo file that lacks `Next', `Previous' and `Up' pointers
(@pxref{Writing a Node}).  Thus, in general, there is no need for explicit
`Next', `Previous', and `Up' pointers.  In this setting, menus will be added
automatically for nodes without an explicit menu.  (@xref{Generic Translator
@command{texi2any}}, for more information about @command{texi2any}.)

If you still want explicit pointers, Texinfo mode provides commands for
automatically creating or updating menus and node pointers.  The commands are
called ``update'' commands because their most frequent use is for updating a
Texinfo file after you have worked on it; but you can use them to insert the
`Next', `Previous', and `Up' pointers into an @code{@@node} line that has none
and to create menus in a file that has none.


@node Updating Commands
@nodedescription Five major updating commands.
@subsection The Updating Commands

You can use the updating commands to:

@itemize @bullet
@item
insert or update the `Next', `Previous', and `Up' pointers of a node,

@item
insert or update the menu for a section, and

@item
create a master menu for a Texinfo source file.
@end itemize

You can also use the commands to update all the nodes and menus in a
region or in a whole Texinfo file.

The updating commands work only with conventional Texinfo files, which
are structured hierarchically like books.  In such files, a line with a
structuring command must follow closely after each @code{@@node} line,
except for the `Top' @code{@@node} line.

You can write the structuring command on the line that follows
immediately after an @code{@@node} line or else on the line that
follows after a single @code{@@comment} line or a single
@code{@@ifinfo} line.  You cannot interpose more than one line between
the @code{@@node} line and the structuring command line; and you may
interpose only a @code{@@comment} line or an @code{@@ifinfo} line.

Commands which work on a whole buffer require that the `Top' node be
followed by a node with a @code{@@chapter} or equivalent-level command.
The menu updating commands will not create a main or master menu for a
Texinfo file that has only @code{@@chapter}-level nodes!  The menu
updating commands only create menus @emph{within} nodes for lower level
nodes.  To create a menu of chapters, you must provide a `Top'
node.

The menu updating commands remove menu entries that refer to other Info
files since they do not refer to nodes within the current buffer.  This
is a deficiency.  Rather than use menu entries, you can use cross
references to refer to other Info files.  None of the updating commands
affect cross-references.

Texinfo mode has five updating commands that are used most often: two
are for updating the node pointers or menu of a single node (or a
region); two are for updating every node pointer and menu in a file;
and one, the @code{texinfo-master-menu} command, is for creating a
master menu for a complete file, and optionally, for updating every
node and menu in the whole Texinfo file.

The @code{texinfo-master-menu} command is the primary command:

@table @kbd
@findex texinfo-master-menu
@item C-c C-u m
@itemx M-x texinfo-master-menu
Create or update a master menu that includes all the other menus
(incorporating the descriptions from pre-existing menus, if
any).

With an argument (prefix argument, @kbd{C-u,} if interactive), first create or
update all the nodes and all the regular menus in the buffer before
constructing the master menu.  (@xref{The Top Node, , The Top Node and
Master Menu}, for more about a master menu.)

For @code{texinfo-master-menu} to work, the Texinfo file must have a
`Top' node and at least one subsequent node.

After extensively editing a Texinfo file, you can type the following:

@example
C-u M-x texinfo-master-menu
@exdent or
C-u C-c C-u m
@end example

@noindent
This updates all the nodes and menus completely and all at once.
@end table

The other major updating commands do smaller jobs and are designed for
the person who updates nodes and menus as he or she writes a Texinfo
file.

@need 1000
The commands are:

@table @kbd
@findex texinfo-update-node
@item C-c C-u C-n
@itemx M-x texinfo-update-node
Insert the `Next', `Previous', and `Up' pointers for the node that point is
within (i.e., for the @code{@@node} line preceding point).  If the
@code{@@node} line has pre-existing `Next', `Previous', or `Up'
pointers in it, the old pointers are removed and new ones inserted.
With an argument (prefix argument, @kbd{C-u}, if interactive), this command
updates all @code{@@node} lines in the region (which is the text
between point and mark).

@findex texinfo-make-menu
@item C-c C-u C-m
@itemx M-x texinfo-make-menu
Create or update the menu in the node that point is within.
With an argument (@kbd{C-u} as prefix argument, if
interactive), the command makes or updates menus for the
nodes which are either within or a part of the
region.

Whenever @code{texinfo-make-menu} updates an existing menu, the
descriptions from that menu are incorporated into the new menu.  This
is done by copying descriptions from the existing menu to the entries
in the new menu that have the same node names.  If the node names are
different, the descriptions are not copied to the new menu.

@findex texinfo-every-node-update
@item C-c C-u C-e
@itemx M-x texinfo-every-node-update
Insert or update the `Next', `Previous', and `Up' pointers for every
node in the buffer.

@findex texinfo-all-menus-update
@item C-c C-u C-a
@itemx M-x texinfo-all-menus-update
Create or update all the menus in the buffer.  With an argument
(@kbd{C-u} as prefix argument, if interactive), first insert
or update all the node
pointers before working on the menus.

If a master menu exists, the @code{texinfo-all-menus-update} command
updates it; but the command does not create a new master menu if none
already exists.  (Use the @code{texinfo-master-menu} command for
that.)

When working on a document that does not merit a master menu, you can
type the following:

@example
C-u C-c C-u C-a
@exdent or
C-u M-x texinfo-all-menus-update
@end example

@noindent
This updates all the nodes and menus.
@end table

The @code{texinfo-column-for-description} variable specifies the
column to which menu descriptions are indented.  By default, the value
is 32 although it can be useful to reduce it to as low as 24.  You
can set the variable via customization (@pxref{Customization,,,
emacs, The GNU Emacs Manual}) or with the @kbd{M-x set-variable}
command (@pxref{Examining, , Examining and Setting Variables, emacs,
The GNU Emacs Manual}).

Also, the @code{texinfo-indent-menu-description} command may be used to
indent existing menu descriptions to a specified column.  Finally, if
you wish, you can use the @code{texinfo-insert-node-lines} command to
insert missing @code{@@node} lines into a file.  In particular, you can
ignore @code{@@node} lines altogether in your first draft and then
use the @code{texinfo-insert-node-lines} command to create @code{@@node}
lines for you.  However, we do not recommend this practice.  It is better
to name the node itself at the same time that you write a segment so you
can easily make cross-references.  Useful cross-references are an
especially important feature of a good Texinfo manual.
(@xref{Other Updating Commands}, for more information.)


@node Updating Requirements
@nodedescriptionblock
How to structure a Texinfo file for using the updating command.
@end nodedescriptionblock
@subsection Updating Requirements
@cindex Updating requirements
@cindex Requirements for updating commands

To use the updating commands, you must organize the Texinfo file
hierarchically with chapters, sections, subsections, and the like.
When you construct the hierarchy of the manual, do not `jump down'
more than one level at a time: you can follow the `Top' node with a
chapter, but not with a section; you can follow a chapter with a
section, but not with a subsection.  However, you may `jump up' any
number of levels at one time---for example, from a subsection to a
chapter.

Each @code{@@node} line, with the exception of the line for the `Top'
node, must be followed by a line with a structuring command such as
@code{@@chapter}, @code{@@section}, or
@code{@@unnumberedsubsec}.

Each @code{@@node} line/structuring-command line combination
must look either like this:

@example
@group
@@node     Comments,  Minimum, Conventions, Overview
@@comment  node-name, next,    previous,    up
@@section Comments
@end group
@end example

or like this (without the @code{@@comment} line):

@example
@group
@@node Comments, Minimum, Conventions, Overview
@@section Comments
@end group
@end example

or like this (without the explicit node pointers):

@example
@group
@@node Comments
@@section Comments
@end group
@end example

@noindent
In this example, `Comments' is the name of both the node and the
section.  The next node is called `Minimum' and the previous node is
called `Conventions'.  The `Comments' section is within the `Overview'
node, which is specified by the `Up' pointer.

If a file has a `Top' node, it must be called @samp{top} or @samp{Top}
and be the first node in the file.

The menu updating commands create a menu of sections within a chapter,
a menu of subsections within a section, and so on.  This means that
you must have a `Top' node if you want a menu of chapters.


@node Update Multiple Files
@nodedescriptionblock
How to create and update nodes and menus when using included files.
@end nodedescriptionblock
@subsection Update Outer File and Include Files

@anchor{@code{texinfo-multiple-files-update}}@c old node name

@findex texinfo-multiple-files-update

GNU Emacs Texinfo mode provides the
@code{texinfo-multiple-files-update} command.  This command creates or
updates `Next', `Previous', and `Up' pointers of included files as
well as those in the outer or overall Texinfo file, and it creates or
updates a main menu in the outer file.  Depending on whether you call
it with optional arguments, the command updates only the pointers in
the first @code{@@node} line of the included files or all of them.

With @kbd{C-u} as a prefix argument, create and insert a master menu in
the outer file.  With a numeric prefix argument, such as @kbd{C-u 2}, first
update all the menus and all the `Next', `Previous', and `Up' pointers
of all the included files before creating and inserting a master menu in
the outer file.

In more details:

@table @kbd
@item M-x texinfo-multiple-files-update
Called without any arguments:

@itemize @minus
@item
Create or update the `Next', `Previous', and `Up' pointers of the
first @code{@@node} line in each file included in an outer or overall
Texinfo file.

@item
Create or update the `Top' level node pointers of the outer or
overall file.

@item
Create or update a main menu in the outer file.
@end itemize

@item C-u M-x texinfo-multiple-files-update
Called with @kbd{C-u} as a prefix argument:

@itemize @minus{}
@item
Create or update pointers in the first @code{@@node} line in each
included file.

@item
Create or update the `Top' level node pointers of the outer file.

@item
Create and insert a master menu in the outer file.  The master menu
is made from all the menus in all the included files.
@end itemize

@item C-u 8 M-x texinfo-multiple-files-update
Called with a numeric prefix argument, such as @kbd{C-u 8}:

@itemize @minus
@item
Create or update @emph{all} the `Next', `Previous', and `Up' pointers
of all the included files.

@item
Create or update @emph{all} the menus of all the included
files.

@item
Create or update the `Top' level node pointers of the outer or
overall file.

@item
And then create a master menu in the outer file.  This is similar to
invoking @code{texinfo-master-menu} with an argument when you are
working with just one file.
@end itemize
@end table

Note the use of the prefix argument in interactive use: with a regular
prefix argument, just @w{@kbd{C-u}}, the
@code{texinfo-multiple-files-update} command inserts a master menu;
with a numeric prefix argument, such as @kbd{C-u 8}, the command
updates @emph{every} pointer and menu in @emph{all} the files and
then inserts a master menu.


@node Include Files Requirements
@nodedescriptionblock
How to structure outer file and include files for the updating command.
@end nodedescriptionblock
@subsection Include Files Requirements
@cindex Include files requirements
@cindex Requirements for include files

If you plan to use the @code{texinfo-multiple-files-update} command,
the outer Texinfo file that lists included files within it should
contain nothing but the beginning and end parts of a Texinfo file, and
a number of @code{@@include} commands listing the included files.  It
should not even include indices, which should be listed in an included
file of their own.

Moreover, each of the included files must contain exactly one highest
level node (conventionally, @code{@@chapter} or equivalent),
and this node must be the first node in the included file.
Furthermore, each of these highest level nodes in each included file
must be at the same hierarchical level in the file structure.
Usually, each is a @code{@@chapter}, an @code{@@appendix}, or an
@code{@@unnumbered} node.  Thus, normally, each included file contains
one, and only one, chapter or equivalent-level node.

The outer file should contain only @emph{one} node, the `Top' node.  It
should @emph{not} contain any nodes besides the single `Top' node.  The
@code{texinfo-multiple-files-update} command will not process
them.


@node Other Updating Commands
@nodedescriptionblock
How to indent descriptions, insert missing nodes lines, and update
nodes in sequence.
@end nodedescriptionblock
@subsection Other Updating Commands

In addition to the major updating commands, Texinfo mode possesses several
less frequently used updating commands:

@table @kbd
@findex texinfo-insert-node-lines
@item M-x texinfo-insert-node-lines
Insert @code{@@node} lines before the @code{@@chapter},
@code{@@section}, and other sectioning commands wherever they are
missing throughout a region in a Texinfo file.

With an argument (@kbd{C-u} as prefix argument, if interactive), the
command @code{texinfo-insert-node-lines} not only inserts
@code{@@node} lines but also inserts the chapter or section titles as
the names of the corresponding nodes.  In addition, it inserts the
titles as node names in pre-existing @code{@@node} lines that lack
names.  Since node names should be more concise than section or
chapter titles, you must manually edit node names so inserted.

For example, the following marks a whole buffer as a region and inserts
@code{@@node} lines and titles throughout:

@example
C-x h C-u M-x texinfo-insert-node-lines
@end example

This command inserts titles as node names in @code{@@node} lines; the
@code{texinfo-start-menu-description} command (@pxref{Inserting,
Inserting Frequently Used Commands}) inserts titles as descriptions in
menu entries, a different action.  However, in both cases, you need to
edit the inserted text.

@findex texinfo-indent-menu-description
@item M-x texinfo-indent-menu-description
Indent every description in the menu following point to the specified
column.  You can use this command to give yourself more space for
descriptions.  With an argument (@kbd{C-u} as prefix argument, if
interactive), the @code{texinfo-indent-menu-description} command indents
every description in every menu in the region.  However, this command
does not indent the second and subsequent lines of a multi-line
description.

@findex texinfo-sequential-node-update
@item M-x texinfo-sequential-node-update
Insert the names of the nodes immediately following and preceding the
current node as the `Next' or `Previous' pointers regardless of those
nodes' hierarchical level.  This means that the `Next' node of a
subsection may well be the next chapter.  Sequentially ordered nodes are
useful for novels and other documents that you read through
sequentially.  (However, in Info, the @kbd{g *} command lets
you look through the file sequentially, so sequentially ordered nodes
are not strictly necessary.)  With an argument (prefix argument, if
interactive), the @code{texinfo-sequential-node-update} command
sequentially updates all the nodes in the region.
@end table


@node Info Formatting
@nodedescription How to format for Info.
@section Formatting for Info
@cindex Formatting for Info
@cindex Running an Info formatter
@cindex Info formatting

Texinfo mode provides several commands for formatting part or all of a
Texinfo file for Info.


@node @command{texi2any} in Emacs
@nodedescription How to run @command{texi2any} from Emacs.
@subsection Running @command{texi2any}/@command{makeinfo} Within Emacs

@c anchor{makeinfo in Emacs}@c prev name
@anchor{@code{makeinfo} in Emacs}@c prev name
@anchor{@command{makeinfo} Advantages}@c node merged in this one
@cindex Running @command{makeinfo} in Emacs
@cindex Running @command{texi2any} in Emacs
@cindex @command{makeinfo} inside Emacs
@cindex @command{texi2any} inside Emacs
@cindex Shell, running @command{makeinfo} in
@cindex Shell, running @command{texi2any} in

The @command{texi2any} program provides better error messages
than either of the Emacs formatting commands.  We recommend it.
The @command{texi2any} program is independent of Emacs.

You can run @command{texi2any} (or @command{makeinfo}) in GNU Emacs
Texinfo mode by using either the @code{makeinfo-region} or the
@code{makeinfo-buffer} commands.  In Texinfo mode, the commands
are bound to @kbd{C-c C-m C-r} and @kbd{C-c C-m C-b} by default.

@table @kbd
@item C-c C-m C-r
@itemx M-x makeinfo-region
Format the current region for Info.
@findex makeinfo-region

@item C-c C-m C-b
@itemx M-x makeinfo-buffer
Format the current buffer for Info.
@findex makeinfo-buffer
@end table

When you invoke @code{makeinfo-region} the output goes to a temporary
@c FIXME or to the file based on input file name?
buffer.  When you invoke @code{makeinfo-buffer} output goes to the
file set with @code{@@setfilename} (@pxref{@code{@@setfilename}}).

The Emacs @code{makeinfo-region} and @code{makeinfo-buffer} commands
run the @command{texi2any} program in a temporary shell buffer.  If
@command{texi2any} finds any errors, Emacs displays the error messages in
the temporary buffer.

@cindex Errors, parsing
@cindex Parsing errors
@findex next-error
You can parse the error messages by typing @kbd{C-x `}
(@code{next-error}).  This causes Emacs to go to and position the
cursor on the line in the Texinfo source that @command{texi2any} thinks
caused the error.  @xref{Compilation, , Running @code{make} or
Compilers Generally, emacs, The GNU Emacs Manual}, for more
information about using the @code{next-error} command.

In addition, you can kill the shell in which the @command{texi2any}
command is running or make the shell buffer display its most recent
output.

@table @kbd
@findex makeinfo-kill-job
@item C-c C-m C-k
@itemx M-x makeinfo-kill-job
Kill the current running @command{texi2any} (or @command{makeinfo}) job
(from @code{makeinfo-region} or @code{makeinfo-buffer}).

@findex makeinfo-recenter-output-buffer
@item C-c C-m C-l
@itemx M-x makeinfo-recenter-output-buffer
Redisplay the @command{texi2any} shell buffer to display its most recent
output.
@end table

@noindent
(Note that the parallel commands for killing and recentering a @TeX{}
job are @kbd{C-c C-t C-k} and @kbd{C-c C-t C-l}.  @xref{Texinfo Mode
Printing}.)

You can specify options for @command{texi2any} by setting the
@code{makeinfo-options} variable with either the @kbd{M-x
customize} or the @kbd{M-x set-variable} command, or by setting the
variable in your @file{.emacs} initialization file.

For example, you could write the following in your @file{.emacs} file:

@example
@group
(setq makeinfo-options
     "--paragraph-indent=0 --no-split
      --fill-column=70 --verbose")
@end group
@end example

@noindent
@c Writing these three cross-references using xref results in
@c three references to the same named manual, which looks strange.
@iftex
For more information, see @ref{@command{texi2any} Options}, as well as
``Easy Customization Interface,'' ``Examining and Setting Variables,''
and ``Init File'' in @cite{The GNU Emacs Manual}.
@end iftex
@ifnottex
For more information, see@*
@ref{Easy Customization, , Easy Customization Interface, emacs, The GNU Emacs Manual},@*
@ref{Examining, , Examining and Setting Variables, emacs, The GNU Emacs Manual},@*
@ref{Init File, , , emacs, The GNU Emacs Manual}, and@*
@ref{@command{texi2any} Options}.
@end ifnottex


@node @code{texinfo-format} commands
@nodedescriptionblock
Two Info formatting commands written in Emacs Lisp are an alternative
to @command{texi2any}.
@end nodedescriptionblock
@subsection The @code{texinfo-format@dots{}} Commands

@c anchor{texinfo-format commands}@c prev name

In GNU Emacs in Texinfo mode, you can format part or all of a Texinfo
file with the @code{texinfo-format-region} command.  This formats the
current region and displays the formatted text in a temporary buffer
called @samp{*Info Region*}.

Similarly, you can format a buffer with the
@code{texinfo-format-buffer} command.  This command creates a new
buffer and generates the Info file in it.  Typing @kbd{C-x C-s} will
save the Info file under the name specified by the
@code{@@setfilename} line which must be near the beginning of the
Texinfo file.

@table @kbd
@findex texinfo-format-region
@item C-c C-e C-r
@itemx @code{texinfo-format-region}
Format the current region for Info.

@findex texinfo-format-buffer
@item C-c C-e C-b
@itemx @code{texinfo-format-buffer}
Format the current buffer for Info.
@end table

The @code{texinfo-format-region} and @code{texinfo-format-buffer}
commands provide you with some error checking, and other functions can
provide you with further help in finding formatting errors.  These
procedures are described in an appendix; see @ref{Catching Mistakes}.
However, the @command{texi2any} program provides better error checking
(@pxref{@command{texi2any} in Emacs}).

A peculiarity of the @code{texinfo-format-buffer} and
@code{texinfo-format-region} commands is that they do not indent (nor
fill) paragraphs that contain @code{@@w} or @code{@@*} commands.


@node Printing with Emacs
@nodedescription How to format with @TeX{} and print with Emacs.
@section Formatting and Printing with Emacs

GNU Emacs can be used for formatting and printing with @TeX{},
from an Emacs Shell.  Texinfo mode also provides predefined
key commands for formatting and printing.


@node Texinfo Mode Printing
@nodedescription How to format and print part or all of a file.
@subsection Formatting and Printing in Texinfo Mode
@cindex Region printing in Texinfo mode
@cindex Format and print in Texinfo mode
@cindex Print and format in Texinfo mode

Texinfo mode provides several predefined key commands for @TeX{}
formatting and printing.  These include commands for sorting indices,
looking at the printer queue, killing the formatting job, and
recentering the display of the buffer in which the operations
occur.

@cindex Printing a region or buffer
@cindex Region formatting and printing
@cindex Buffer formatting and printing
@cindex Part of file formatting and printing
Often, when you are writing a document, you want to typeset and print
only part of a file to see what it will look like.  You can use the
@code{texinfo-tex-region} and related commands for this purpose.  Use
the @code{texinfo-tex-buffer} command to format all of a
buffer.

For @code{texinfo-tex-region} or @code{texinfo-tex-buffer} to work, the
file @emph{must} start with a @samp{\input texinfo} line and must
include a @code{@@settitle} line.  The file must end with @code{@@bye}
on a line by itself.  (When you use @code{texinfo-tex-region}, you must
surround the @code{@@settitle} line with start-of-header and
end-of-header lines.)

@table @kbd
@findex texinfo-tex-buffer
@item C-c C-t C-b
@itemx M-x texinfo-tex-buffer
Run @command{texi2dvi} on the buffer.  In addition to running @TeX{} on the
buffer, this command automatically creates or updates indices as
needed.

@item C-c C-t C-r
@itemx M-x texinfo-tex-region
Run @TeX{} on the current region.

If @@-commands related to printed output are between the
start-of-header and end-of-header lines, then
@code{texinfo-tex-region} will format the
region accordingly.  For example, if you write the @code{@@smallbook} command
between the start-of-header and end-of-header lines, @code{texinfo-tex-region},
will format the region in ``small'' book size.

@item C-c C-t C-i
@itemx M-x texinfo-texindex
Run @command{texindex} to sort the indices of a Texinfo file formatted with
@code{texinfo-tex-region}.  The @code{texinfo-tex-region} command does
not run @command{texindex} automatically; it only runs the @command{tex}
typesetting command.  You must run the @code{texinfo-tex-region} command
a second time after sorting the raw index files with the @command{texindex}
command.  (Usually, you do not format an index when you format a region,
only when you format a buffer.  Now that the @command{texi2dvi} command
exists, there is little or no need for this command.)

@item C-c C-t C-p
@itemx M-x texinfo-tex-print
Print a DVI file that was made with @code{texinfo-tex-region} or
@code{texinfo-tex-buffer}.

@item C-c C-t C-q
@itemx M-x tex-show-print-queue
Show the print queue.

@item C-c C-t C-d
@itemx M-x texinfo-delete-from-print-queue
Delete a job from the print queue; you will be prompted for the job
number shown by a preceding @kbd{C-c C-t C-q} command
(@code{texinfo-show-tex-print-queue}).

@item C-c C-t C-k
@itemx M-x tex-kill-job
Kill the currently running @TeX{} job started by either
@code{texinfo-tex-region} or @code{texinfo-tex-buffer}, or any other
process running in the Texinfo shell buffer.

@item C-c C-t C-x
@itemx M-x texinfo-quit-job
Quit a @TeX{} formatting job that has stopped because of an error by
sending an @key{x} to it.  When you do this, @TeX{} preserves a record
of what it did in a @file{.log} file.

@item C-c C-t C-l
@itemx M-x tex-recenter-output-buffer
Redisplay the shell buffer in which the @TeX{} printing and formatting
commands are run to show its most recent output.
@end table

@need 1000
Thus, the usual sequence of commands for formatting a buffer is as
follows (with comments to the right):

@example
@group
C-c C-t C-b             @r{Run @command{texi2dvi} on the buffer.}
C-c C-t C-p             @r{Print the DVI file.}
C-c C-t C-q             @r{Display the printer queue.}
@end group
@end example

The Texinfo mode @TeX{} formatting commands start a subshell in Emacs
called the @file{*tex-shell*}.  The @code{texinfo-tex-command},
@code{texinfo-texindex-command}, and @code{tex-dvi-print-command}
commands are all run in this shell.

You can watch the commands operate in the @samp{*tex-shell*} buffer,
and you can switch to and from and use the @samp{*tex-shell*} buffer
as you would any other shell buffer.

@need 1500
The formatting and print commands depend on the values of several variables.
The default values are:

@example
@group
    @r{Variable}                              @r{Default value}

texinfo-texi2dvi-command                  "texi2dvi"
texinfo-tex-command                       "tex"
texinfo-texindex-command                  "texindex"
texinfo-delete-from-print-queue-command   "lprm"
texinfo-tex-trailer                       "@@bye"
tex-start-of-header                       "%**start"
tex-end-of-header                         "%**end"
tex-dvi-print-command                     "lpr -d"
tex-show-queue-command                    "lpq"
@end group
@end example

You can change the values of these variables with the @kbd{M-x
set-variable} command (@pxref{Examining, , Examining and Setting
Variables, emacs, The GNU Emacs Manual}), or with your @file{.emacs}
initialization file (@pxref{Init File, , , emacs, The GNU Emacs
Manual}).

@cindex Customize Emacs package (@t{Development/Docs/Texinfo})
Beginning with version 20, GNU Emacs offers a user-friendly interface,
called @dfn{Customize}, for changing values of user-definable variables.
@xref{Easy Customization, , Easy Customization Interface, emacs, The GNU
Emacs Manual}, for more details about this.  The Texinfo variables can
be found in the @samp{Development/Docs/Texinfo} group, once you invoke
the @kbd{M-x customize} command.


@node Compile-Command
@nodedescription How to print using Emacs's compile command.
@subsection Using the Local Variables List
@cindex Local variables
@cindex Compile command for formatting
@cindex Format with the compile command

Yet another way to apply the @TeX{} formatting command to a Texinfo file
is to put that command in a @dfn{local variables list} at the end of the
Texinfo file.  You can then specify the @command{tex} or @command{texi2dvi}
commands as a @code{compile-command} and have Emacs run it by typing
@kbd{M-x compile}.  This creates a special shell called the
@file{*compilation*} buffer in which Emacs runs the compile command.
For example, at the end of the @file{gdb.texi} file, after the
@code{@@bye}, you could put the following:

@example
@group
Local Variables:
compile-command: "texi2dvi gdb.texi"
End:
@end group
@end example

@noindent
This technique is most often used by programmers who also compile programs
this way; see @ref{Compilation, , , emacs, The GNU Emacs Manual}.




@node Texinfo Mode Summary
@nodedescription Summary of all the Texinfo mode commands.
@section Texinfo Mode Summary

In Texinfo mode, each set of commands has default keybindings that
begin with the same keys.  All the commands that are custom-created
for Texinfo mode begin with @kbd{C-c}.  The keys are somewhat
mnemonic.

@subheading Insert Commands

The insert commands are invoked by typing @kbd{C-c} twice and then the
first letter of the @@-command to be inserted.  (It might make more
sense mnemonically to use @kbd{C-c C-i}, for `custom insert', but
@kbd{C-c C-c} is quick to type.)

@example
C-c C-c c       @r{Insert} @samp{@@code}.
C-c C-c d       @r{Insert} @samp{@@dfn}.
C-c C-c e       @r{Insert} @samp{@@end}.
C-c C-c i       @r{Insert} @samp{@@item}.
C-c C-c n       @r{Insert} @samp{@@node}.
C-c C-c s       @r{Insert} @samp{@@samp}.
C-c C-c v       @r{Insert} @samp{@@var}.
C-c @{       @r{Insert braces.}
C-c ]
C-c @}       @r{Move out of enclosing braces.}

@group
C-c C-c C-d     @r{Insert a node's section title}
               @r{in the space for the description}
               @r{in a menu entry line.}
@end group
@end example

@subheading Show Structure

The @code{texinfo-show-structure} command is often used within a
narrowed region.

@example
C-c C-s         @r{List all the headings.}
@end example

@subheading The Master Update Command

The @code{texinfo-master-menu} command creates a master menu; and can
be used to update every node and menu in a file as well.

@c Probably should use @tables in this section.
@example
@group
C-c C-u m
M-x texinfo-master-menu
               @r{Create or update a master menu.}
@end group

@group
C-u C-c C-u m   @r{With @kbd{C-u} as a prefix argument, first}
               @r{create or update all nodes and regular}
               @r{menus, and then create a master menu.}
@end group
@end example

@subheading Update Pointers

The update pointer commands are invoked by typing @kbd{C-c C-u} and
then either @kbd{C-n} for @code{texinfo-update-node} or @kbd{C-e} for
@code{texinfo-every-node-update}.

@example
C-c C-u C-n     @r{Update a node.}
C-c C-u C-e     @r{Update every node in the buffer.}
@end example

@subheading Update Menus

Invoke the  update menu commands by typing @kbd{C-c C-u}
and then either @kbd{C-m} for @code{texinfo-make-menu} or
@kbd{C-a} for @code{texinfo-all-menus-update}.  To update
both nodes and menus at the same time, precede @kbd{C-c C-u
C-a} with @kbd{C-u}.

@example
C-c C-u C-m     @r{Make or update a menu.}

@group
C-c C-u C-a     @r{Make or update all}
               @r{menus in a buffer.}
@end group

@group
C-u C-c C-u C-a @r{With @kbd{C-u} as a prefix argument,}
               @r{first create or update all nodes and}
               @r{then create or update all menus.}
@end group
@end example

@subheading Format for Info

The Info formatting commands that are written in Emacs Lisp are
invoked by typing @kbd{C-c C-e} and then either @kbd{C-r} for a region
or @kbd{C-b} for the whole buffer.

The Info formatting commands that are based on the
@command{texi2any}/@command{makeinfo} program are invoked by typing
@kbd{C-c C-m} and then either @kbd{C-r} for a region or @kbd{C-b} for
the whole buffer.

@need 800
@noindent
Use the @code{texinfo-format@dots{}} commands:

@example
@group
C-c C-e C-r     @r{Format the region.}
C-c C-e C-b     @r{Format the buffer.}
@end group
@end example

@need 750
@noindent
Use @command{texi2any}/@command{makeinfo}:

@example
C-c C-m C-r     @r{Format the region.}
C-c C-m C-b     @r{Format the buffer.}
C-c C-m C-l     @r{Recenter the @command{texi2any} output buffer.}
C-c C-m C-k     @r{Kill the @command{texi2any} formatting job.}
@end example

@subheading Typeset and Print

The @TeX{} typesetting and printing commands are invoked by typing
@kbd{C-c C-t} and then another control command: @kbd{C-r} for
@code{texinfo-tex-region}, @kbd{C-b} for @code{texinfo-tex-buffer},
and so on.

@example
C-c C-t C-r     @r{Run @TeX{} on the region.}
C-c C-t C-b     @r{Run} @command{texi2dvi} @r{on the buffer.}
C-c C-t C-i     @r{Run} @command{texindex}.
C-c C-t C-p     @r{Print the DVI file.}
C-c C-t C-q     @r{Show the print queue.}
C-c C-t C-d     @r{Delete a job from the print queue.}
C-c C-t C-k     @r{Kill the current @TeX{} formatting job.}
C-c C-t C-x     @r{Quit a currently stopped @TeX{} formatting job.}
C-c C-t C-l     @r{Recenter the output buffer.}
@end example

@subheading Other Updating Commands

The remaining updating commands do not have standard keybindings because
they are rarely used.

@example
@group
M-x texinfo-insert-node-lines
               @r{Insert missing @code{@@node} lines in region.}
               @r{With @kbd{C-u} as a prefix argument,}
               @r{use section titles as node names.}
@end group

@group
M-x texinfo-multiple-files-update
               @r{Update a multi-file document.}
               @r{With @kbd{C-u 2} as a prefix argument,}
               @r{create or update all nodes and menus}
               @r{in all included files first.}
@end group

@group
M-x texinfo-indent-menu-description
               @r{Indent descriptions.}
@end group

@group
M-x texinfo-sequential-node-update
               @r{Insert node pointers in strict sequence.}
@end group
@end example


@node Formatting Info files
@nodedescription Processing directly Info files.
@section Direct Formatting of Info files

@cindex Direct formatting of Info files
In general, there is no need to edit or process Info files.  Most of the
content of Info file is plain text, but the tag tables require computing
offsets for nodes and indirect files (@pxref{Tag and Split Files}), which is
impractical.  The Texinfo processors output well-formatted Info from Texinfo
input.  Also, lot of information from the Texinfo source is lost in the Info
file.  The Texinfo source is therefore more suitable to analyse a manual, be it
for error reporting, for statistics, or to set up translations.

Still, especially with manually written Info files, there are some situations
where it may be interesting to process Info files directly, in particular
to compute Info files node offsets and to compute split Info files file
offsets.  Two Emacs commands do that.  @code{Info-tagify} adds a tag table
for a nonsplit file lacking one.  This function is also useful for Info
file validation (@pxref{Running @code{Info-validate}}).  It is
also possible to split a nonsplit Info file with @code{Info-split}.


@node Tagifying
@nodedescription How to tagify a file.
@subsection Tagifying a File
@cindex Making a tag table manually
@cindex Tag table, making manually
@cindex Info files @subentry making a tag table

Texinfo processors create tag tables automatically.  The only exception
arise when @code{texinfo-format-buffer} is called with a prefix, as
@kbd{C-u M-x texinfo-format-buffer}, to create an non split Info
file without a tag table (which can be useful in some cases for Info file
validation, @pxref{Unsplit and Tagify}).  Adding a tag table is therefore
more generally useful for manually written Info files.

To create a tag table for an nonsplit file, visit the Info file you
wish to tagify and type:

@example
M-x Info-tagify
@end example

@noindent
(Note the uppercase @samp{I} in @code{Info-tagify}.)  This creates an
Info file with a tag table.  A tag table is part of a well formed Info
file (@pxref{Tag and Split Files}).  A tag table is also needed to validate
or split the Info file.


@node Splitting
@nodedescription How to split a file manually.
@subsection Splitting a File Manually
@cindex Splitting an Info file manually
@cindex Info files @subentry splitting manually

You should split a large file or else let the
@code{texinfo-format-buffer} or @code{makeinfo-buffer} command do it
for you automatically.  (Generally you will let one of the formatting
commands do this job for you.  @xref{Info Formatting}.)

The split-off files are called the indirect subfiles.

Tag tables are created automatically by the formatting command;
you only need to create a tag table yourself if you are doing
the job manually.  @xref{Tagifying}, for information about
creating a tag table.

Visit the Info file you wish to tagify and split manually and type the
two commands:

@example
M-x Info-tagify
M-x Info-split
@end example

@noindent
(Note that the @samp{I} in @samp{Info} is uppercase.)

When you use the @code{Info-split} command, the buffer is modified into a
(small) Info file which lists the indirect subfiles.  This file should be
saved in place of the original visited file.  The indirect subfiles are
written in the same directory the original file is in, with names generated
by appending @samp{-} and a number to the original file name.

The primary file still functions as an Info file, but it contains just
the tag table and a directory of subfiles.  @xref{Tag and Split Files}.


@node Catching Mistakes
@nodedescription How to find mistakes in formatting.
@section Catching Mistakes
@cindex Structure, catching mistakes in
@cindex Nodes, catching mistakes
@cindex Catching mistakes
@cindex Correcting mistakes
@cindex Mistakes, catching
@cindex Problems, catching
@cindex Debugging the Texinfo structure

Besides mistakes in the content of your documentation, there are two
kinds of mistake you can make with Texinfo: you can make mistakes with
@@-commands, and you can make mistakes with the structure of the nodes
and chapters.

For finding problems with @@-commands, you can run @TeX{} or a region
formatting command on the region that has a problem; indeed, you can
run these commands on each region as you write it.

For finding problems with the structure of nodes and chapters, you can use
@kbd{C-c C-s} (@code{texinfo-show-structure}) and the related @code{occur}
command and you can use the @kbd{M-x Info-validate} command.


@node @command{texi2any} Preferred
@nodedescription @command{texi2any} finds errors.
@subsection @command{texi2any} Preferred

@c anchor{makeinfo Preferred}@c prev name
@anchor{@code{makeinfo} Preferred}@c prev name

The @command{texi2any} program does an excellent job of catching errors
and reporting them---far better than @code{texinfo-format-region} or
@code{texinfo-format-buffer}.  In addition, the various functions for
automatically creating and updating node pointers and menus remove
many opportunities for human error.

Use @command{texi2any} (or its Texinfo mode manifestations,
@code{makeinfo-region} and @code{makeinfo-buffer}) to format your
file and check for other errors.  This is the best way to work with
Texinfo.  But if you cannot use @command{texi2any}, or your problem
is very puzzling, then you may want to use the tools described
in this section.


@node Debugging with Info
@nodedescription How to catch errors with Info formatting.
@subsection Catching Errors with Info Formatting
@cindex Catching errors with Info formatting
@cindex Debugging with Info formatting

After you have written part of a Texinfo file, you can use the
@code{texinfo-format-region} or the @code{makeinfo-region} command to
see whether the region formats properly.

Most likely, however, you are reading this section because for some
reason you cannot use the @code{makeinfo-region} command; therefore, the
rest of this section presumes that you are using
@code{texinfo-format-region}.

If you have made a mistake with an @@-command,
@code{texinfo-format-region} will stop processing at or after the
error and display an error message.  To see where in the buffer the
error occurred, switch to the @samp{*Info Region*} buffer; the cursor
will be in a position that is after the location of the error.  Also,
the text will not be formatted after the place where the error
occurred (or more precisely, where it was detected).

For example, if you accidentally end a menu with the command @code{@@end
menus} with an `s' on the end, instead of with @code{@@end menu}, you
will see an error message that says:

@example
@@end menus is not handled by texinfo
@end example

@noindent
The cursor will stop at the point in the buffer where the error
occurs, or not long after it.  The buffer will look like this:

@example
@group
---------- Buffer: *Info Region* ----------
* Menu:

* Using texinfo-show-structure::  How to use
                                 `texinfo-show-structure'
                                 to catch mistakes.
* Running Info-validate::         How to check for
                                 unreferenced nodes.
@@end menus
@point{}
---------- Buffer: *Info Region* ----------
@end group
@end example

The @code{texinfo-format-region} command sometimes provides slightly
odd error messages.  For example, the following cross-reference fails
to format:

@example
(@@xref@{Catching Mistakes, for more info.)
@end example

@noindent
In this case, @code{texinfo-format-region} detects the missing closing
brace but displays a message that says @samp{Unbalanced parentheses}
rather than @samp{Unbalanced braces}.  This is because the formatting
command looks for mismatches between braces as if they were
parentheses.

Sometimes @code{texinfo-format-region} fails to detect mistakes.  For
example, in the following, the closing brace is swapped with the
closing parenthesis:

@example
(@@xref@{Catching Mistakes), for more info.@}
@end example

@noindent
Formatting produces:
@example
(*Note for more info.: Catching Mistakes)
@end example

The only way for you to detect this error is to realize that the
reference should have looked like this:

@example
(*Note Catching Mistakes::, for more info.)
@end example

Incidentally, if you are reading this node in Info and type @kbd{f
@key{RET}} (@code{Info-follow-reference}), you will generate an error
message that says:

@example
No such node: "Catching Mistakes) The only way @dots{}
@end example

@noindent
This is because Info perceives the example of the error as the first
cross-reference in this node and if you type a @key{RET} immediately
after typing the Info @kbd{f} command, Info will attempt to go to the
referenced node.  If you type @kbd{f catch @key{TAB} @key{RET}}, Info
will complete the node name of the correctly written example and take
you to the `Catching Mistakes' node.  (If you try this, you can return
from the `Catching Mistakes' node by typing @kbd{l}
(@code{Info-last}).)


@node Debugging with @TeX{}
@nodedescription How to catch errors with @TeX{} formatting.
@subsection Debugging with @TeX{}
@cindex Catching errors with @TeX{} formatting
@cindex Debugging with @TeX{} formatting

You can also catch mistakes when you format a file with @TeX{}.

Usually, you will want to do this after you have run
@code{texinfo-format-buffer} (or, better, @code{makeinfo-buffer}) on
the same file, because @code{texinfo-format-buffer} sometimes displays
error messages that make more sense than @TeX{}.  (@xref{Debugging
with Info}, for more information.)

For example, @TeX{} was run on a Texinfo file, part of which is shown
here:

@example
---------- Buffer: texinfo.texi ----------
name of the Texinfo file as an extension.  The
@@samp@{??@} are `wildcards' that cause the shell to
substitute all the raw index files.  (@@xref@{sorting
indices, for more information about sorting
indices.)
---------- Buffer: texinfo.texi ----------
@end example

@noindent
(The cross-reference lacks a closing brace.)
@TeX{} produced the following output, after which it stopped:

@example
---------- Buffer: *tex-shell* ----------
Runaway argument?
@{sorting indices, for more information about sorting
indices.) @@ETC.
! Paragraph ended before @@xref was complete.
<to be read again>
                  @@par
l.27

?
---------- Buffer: *tex-shell* ----------
@end example

In this case, @TeX{} produced an accurate and
understandable error message:

@example
Paragraph ended before @@xref was complete.
@end example

@noindent
@samp{@@par} is an internal @TeX{} command of no relevance to Texinfo.
@samp{l.27} means that @TeX{} detected the problem on line 27 of the
Texinfo file.  The @samp{?} is the prompt @TeX{} uses in this
circumstance.

Unfortunately, @TeX{} is not always so helpful, and sometimes you must
truly be a Sherlock Holmes to discover what went wrong.

In any case, if you run into a problem like this, you can do one of three
things.

@enumerate
@item
You can tell @TeX{} to continue running and ignore just this error by
typing @key{RET} at the @samp{?} prompt.

@item
You can tell @TeX{} to continue running and to ignore all errors as best
it can by typing @kbd{r @key{RET}} at the @samp{?} prompt.

This is often the best thing to do.  However, beware: the one error
may produce a cascade of additional error messages as its consequences
are felt through the rest of the file.  To stop @TeX{} when it is
producing such an avalanche of error messages, type @kbd{C-c} (or
@kbd{C-c C-c}, if you are running a shell inside Emacs).

@item
You can tell @TeX{} to stop this run by typing @kbd{x @key{RET}}
at the @samp{?} prompt.
@end enumerate

If you are running @TeX{} inside Emacs, you need to switch to the shell
buffer and line at which @TeX{} offers the @samp{?} prompt.

Sometimes @TeX{} will format a file without producing error messages even
though there is a problem.  This usually occurs if a command is not ended
but @TeX{} is able to continue processing anyhow.  For example, if you fail
to end an itemized list with the @code{@@end itemize} command, @TeX{} will
write a DVI file that you can print out.  The only error message that
@TeX{} will give you is the somewhat mysterious comment:

@example
(@@end occurred inside a group at level 1)
@end example

@noindent
However, if you print the DVI file, you will find that the text
of the file that follows the itemized list is entirely indented as if
it were part of the last item in the itemized list.  The error message
is the way @TeX{} says that it expected to find an @code{@@end}
command somewhere in the file; but that it could not determine where
it was needed.

Another source of notoriously hard-to-find errors is a missing
@code{@@end group} command.  If you ever are stumped by
incomprehensible errors, look for a missing @code{@@end group} command
first.

If the Texinfo file lacks header lines,
@TeX{} may stop in the
beginning of its run and display output that looks like the following.
The @samp{*} indicates that @TeX{} is waiting for input.

@example
This is TeX, Version 3.14159 (Web2c 7.0)
(test.texinfo [1])
*
@end example

@noindent
In this case, simply type @kbd{\end @key{RET}} after the asterisk.  Then
write the header lines in the Texinfo file and run the @TeX{} command
again. (Note the use of the backslash, @samp{\}.  @TeX{} uses @samp{\}
instead of @samp{@@}; and in this circumstance, you are working
directly with @TeX{}, not with Texinfo.)


@node Running @code{Info-validate}
@nodedescription How to find badly referenced nodes.
@subsection Finding Badly Referenced Nodes

@anchor{Running Info-Validate}@c old name
@findex Info-validate
@cindex Nodes, checking for badly referenced
@cindex Checking for badly referenced nodes
@cindex Looking for badly referenced nodes
@cindex Finding badly referenced nodes
@cindex Badly referenced nodes

You can use the @code{Info-validate} command to check whether any of
the `Next', `Previous', `Up' or other node pointers fail to point to a
node.  This command checks that every node pointer points to an
existing node.  The @code{Info-validate} command works only on Info
files, not on Texinfo files.

The @command{texi2any} program validates pointers automatically, so you
do not need to use the @code{Info-validate} command if you are using
@command{texi2any}.  With the customization variable
@code{CHECK_NORMAL_MENU_STRUCTURE} set, @command{texi2any} will also
warn if the nodes pointers (either explicitly or automatically set)
are not consistent with the order of node menu entries.
@command{texi2any} does not check that every `Next' pointer is matched
by a `Previous' (in the node where the `Next' points) which points back,
since it may be correct for a non standard document structure.

You only may need to use @code{Info-validate} if you
are unable to run @command{texi2any} and instead must create an Info file
using @code{texinfo-format-region} or @code{texinfo-format-buffer}, or
if you write an Info file from scratch.


@node Using @code{Info-validate}
@nodedescription How to run @code{Info-validate}.
@subsubsection Using @code{Info-validate}

@cindex Using @code{Info-validate}
@cindex Info validating a large file
@cindex Validating a large file

To use @code{Info-validate}, visit the Info file you wish to check and
type:

@example
M-x Info-validate
@end example

@noindent
Note that the @code{Info-validate} command requires an uppercase
`I'@.  You may also need to create a tag table before running
@code{Info-validate}.  @xref{Tagifying}.

If your file is valid, you will receive a message that says ``File appears
valid''.  However, if you have a pointer that does not point to a node,
error messages will be displayed in a buffer called @samp{*problems in
info file*}.

For example, @code{Info-validate} was run on a test file that contained
only the first node of this manual.  One of the messages said:

@example
In node "Overview", invalid Next: Texinfo Mode
@end example

@noindent
This meant that the node called @samp{Overview} had a `Next' pointer that
did not point to anything (which was true in this case, since the test file
had only one node in it).

Now suppose we add a node named @samp{Texinfo Mode} to our test case
but we do not specify a `Previous' for this node.  Then we will get
the following error message:

@example
In node "Texinfo Mode", should have Previous: Overview
@end example

@noindent
This is because, with a standard document structure, every `Next' pointer
should be matched by a `Previous' (in the node where the `Next' points)
which points back.

@code{Info-validate} also checks that all menu entries and cross-references
point to actual nodes.

@code{Info-validate} requires a tag table and does not work with files
that have been split.  (The @code{texinfo-format-buffer} command
automatically splits large files.)  In order to use @code{Info-validate}
on a large file, you must run @code{texinfo-format-buffer} with an
argument so that it does not split the Info file; and you must create a
tag table for the unsplit file.


@node Unsplit and Tagify
@nodedescriptionblock
How to create an unsplit file and add a tag table for validation.
@end nodedescriptionblock
@subsubsection Creating an Unsplit File and Adding a Tag Table
@anchor{Unsplit} @c old name

@cindex Creating an unsplit file
@cindex Unsplit file creation

You can run @code{Info-validate} only on a single Info file that has a
tag table.  The command will not work on the indirect subfiles that
are generated when a master file is split.  If you have a large file
(longer than 300,000 bytes or so), you need to run the
@code{texinfo-format-buffer} or @code{makeinfo-buffer} command in such
@c FIXME probably always a tag table with makeinfo-buffer?
a way that it does not create indirect subfiles.  You will also need
to create a tag table for the Info file.  After you have done this,
you can run @code{Info-validate} and look for badly referenced
nodes.

The first step is to create an unsplit Info file.  To prevent
@code{texinfo-format-buffer} from splitting a Texinfo file into
smaller Info files, give a prefix to the @kbd{M-x
texinfo-format-buffer} command:

@example
C-u M-x texinfo-format-buffer
@end example

@noindent
or else

@example
C-u C-c C-e C-b
@end example

@noindent
When you do this, @code{texinfo-format-buffer} will not split the file and will
not create a tag table for it.

After creating an unsplit Info file, you must create a tag table for
it (@pxref{Tagifying}).  Visit the unsplit Info file created by
@code{texinfo-format-buffer} and type:

@example
M-x Info-tagify
@end example

The third step is to validate the Info file:

@example
M-x Info-validate
@end example

@noindent
(Note the uppercase @samp{I} in @code{Info-validate}.)
In brief, the steps are:

@example
@group
C-u M-x texinfo-format-buffer
M-x Info-tagify
M-x Info-validate
@end group
@end example

After you have validated the node structure, you can rerun
@code{texinfo-format-buffer} in the normal way so it will construct a
tag table and split the file automatically, or you can make the tag
table and split the file manually (@pxref{Splitting}).


@node Batch Formatting
@nodedescription How to format for Info in Emacs batch mode.
@section Batch Formatting
@cindex Batch formatting for Info
@cindex Info batch formatting

You can format Texinfo files for Info using @code{batch-texinfo-format}
and Emacs batch mode.  You can run Emacs in batch mode from any shell,
including a shell inside of Emacs.  (@xref{Initial Options,,,
emacs, The GNU Emacs Manual}.)

Here is a shell command to format all the files that end in
@file{.texinfo} in the current directory:

@example
emacs -batch -funcall batch-texinfo-format *.texinfo
@end example

@noindent
Emacs processes all the files listed on the command line, even if an
error occurs while attempting to format some of them.

Run @code{batch-texinfo-format} only with Emacs in batch mode as shown;
it is not interactive.  It kills the batch mode Emacs on completion.

@code{batch-texinfo-format} is convenient if you lack @command{texi2any}
and want to format several Texinfo files at once.  When you use Batch
mode, you create a new Emacs process.  This frees your current Emacs, so
you can continue working in it.  (When you run
@code{texinfo-format-region} or @code{texinfo-format-buffer}, you cannot
use that Emacs for anything else until the command finishes.)


@node Global Document Commands
@nodedescription Affecting formatting throughout.
@appendix Global Document Commands
@cindex Global Document Commands

Here are additional commands which affect the document as a whole.  Most
of these commands are for customizing the appearance of the printed output.
They are generally all given before the Top node, if they are given at all.


@node @code{@@setchapternewpage}
@nodedescription Start chapters on right-hand pages.
@section @code{@@setchapternewpage}: Blank Pages Before Chapters

@anchor{setchapternewpage}@c old name
@findex setchapternewpage
@cindex Starting chapters
@cindex Pages, starting odd

In an officially bound book, text is usually printed on both sides of
the paper, chapters start on right-hand pages, and right-hand pages have
odd numbers.  But in short reports, text often is printed only on one
side of the paper.  Also in short reports, chapters sometimes do not
start on new pages, but are printed on the same page as the end of the
preceding chapter, after a small amount of vertical whitespace.

You can use the @code{@@setchapternewpage} command with various
arguments to specify how chapters should be started in printed output
and whether headers should be formatted for printing on one or both sides of
the paper (single-sided or double-sided printing).

Write the @code{@@setchapternewpage} command at the beginning of a
line followed by its argument.  For example, you would write the 
following to cause each chapter to start on a fresh odd-numbered page:

@example
@@setchapternewpage odd
@end example

You can specify one of three alternatives with the
@code{@@setchapternewpage} command:

@table @asis

@item @code{@@setchapternewpage off}
Typeset a new chapter on the same page as the last chapter, after
skipping some vertical whitespace.  Also, format page headers for
single-sided printing.

@item @code{@@setchapternewpage on}
Start new chapters on new pages and format page headers for
single-sided printing.  This is the form most often used for short
reports or personal printing. This is the default.

@item @code{@@setchapternewpage odd}
Start new chapters on new, odd-numbered pages (right-handed pages)
and typeset for double-sided printing.  This is the form most often
used for books and manuals.
@end table

Texinfo does not have a @code{@@setchapternewpage even} command,
because there is no printing tradition of starting chapters or books on
an even-numbered page.

If you don't like the default headers that @code{@@setchapternewpage}
sets, you can explicit control them with the @code{@@headings} command.
@xref{@code{@@headings}}.

At the beginning of a manual or book, pages are not numbered---for
example, the title and copyright pages of a book are not numbered.  By
convention, table of contents and front matter pages are numbered with
roman numerals and not in sequence with the rest of the document.

The @code{@@setchapternewpage} has no effect in output formats that do
not have pages, such as Info and HTML.

We recommend not including any @code{@@setchapternewpage} command in
your document source at all, since such desired pagination is not
intrinsic to the document.  For a particular hard copy run, if you
don't want the default output (no blank pages, same headers on all
pages) use the @option{--texinfo} option to @command{texi2dvi} to
specify the output you want.


@node Headings
@section Page Headings
@nodedescription Page headings.
@anchor{Headings Introduced}@c old name
@cindex Headings
@cindex Footings
@cindex Page numbering
@cindex Page headings
@cindex Formatting headings and footings

Most printed manuals contain headings along the top of every page
except the title and copyright pages.  Some manuals also contain
footings. @c HTML output also supports something like these, but in a
@c completely different way: @pxref{Customizing HTML Page Layout}.
Headings and footings have no meaning in Info or the other output
formats.

Texinfo provides two standard heading formats, one for manuals printed
on one side of each sheet of paper, and the other for manuals printed
on both sides of the paper.
By default, nothing is specified for the footing of a Texinfo file,
so the footing remains blank.

Texinfo also has several heading and footing commands that you
can use to generate your own heading and footing formats.

In Texinfo, headings and footings are single lines at the tops and
bottoms of pages; you cannot create multiline headings or footings.
Each header or footer line is divided into three parts: a left part, a
middle part, and a right part.  Any part, or a whole line, may be left
blank.  Text for the left part of a header or footer line is set
flushleft; text for the middle part is centered; and text for the
right part is set flushright.


@node @code{@@headings}
@nodedescriptionblock
An option for turning headings on and off and double or single sided printing.
@end nodedescriptionblock
@subsection The @code{@@headings} Command

@anchor{headings on off}@c old name
@findex headings

The @code{@@headings} command is rarely used.  It specifies what kinds of
page headings and footings to print on each page.  Usually, this is
controlled by the @code{@@setchapternewpage} command.  You need the
@code{@@headings} command only if the @code{@@setchapternewpage} command
does not do what you want.

You can use @code{@@headings} as follows:

@table @code
@item @@headings off
Turn off printing of page headings.

@item @@headings single
Turn on page headings appropriate for single-sided printing.

@item @@headings double
Turn on page headings appropriate for double-sided printing.

@item @@headings singleafter
@itemx @@headings doubleafter
Turn on @code{single} or @code{double} headings, respectively, after the
current page is output.

@item @@headings on
Turn on page headings: @code{single} if @samp{@@setchapternewpage
on}, @code{double} otherwise.
@end table

For example, suppose you write @code{@@setchapternewpage off} before the
@code{@@titlepage} command to start a new chapter on the
same page as the end of the last chapter.  This command also causes
page headers to be typeset for single-sided printing.  To cause
page headers to be typeset for double-sided printing, write @code{@@headings
double}.

You can stop any page headings at all from being generated by writing
@code{@@headings off} on a line of its own, like this:

@example
@@headings off
@end example


@node Heading Format
@nodedescription Standard page heading formats.
@subsection Standard Heading Formats

Texinfo provides two standard heading formats, one for manuals printed
on one side of each sheet of paper, and the other for manuals printed
on both sides of the paper.

The standard format for single-sided printing consists of a header
line in which the left-hand part contains the name of the chapter, the
central part is blank, and the right-hand part contains the page
number.   A single-sided page looks like this:

@example
@group
  _______________________
 |                       |
 | chapter   page number |
 |                       |
 | Start of text ...     |
 | ...                   |
 |                       |
@end group
@end example

In the standard double-sided format, the left part of the left-hand
(even-numbered) page contains the page number, the central part is
blank, and the right part contains the title (specified by the
@code{@@settitle} command).  The left part of the right-hand
(odd-numbered) page contains the name of the chapter, the central part
is blank, and the right part contains the page number.
An even-numbered page and an odd-numbered page, side by side as in an
open book, look like this:

@example
@group
  _______________________     _______________________
 |                       |   |                       |
 | page number     title |   | chapter   page number |
 |                       |   |                       |
 | Start of text ...     |   | More  text ...        |
 | ...                   |   | ...                   |
 |                       |   |                       |
@end group
@end example

@noindent
The chapter name is preceded by the word ``Chapter'', the chapter number
and a colon.  This makes it easier to keep track of where you are in the
manual.

Note that on pages where a new chapter starts, some text may be omitted
from the heading line.

@ignore
@c not germane to headings?  we don't document \bindingoffset or \normaloffset
@c anywhere.
In double sided printing, @TeX{} will adjust the
widths of the left- and right-hand margins.  Usually, widths are
correct, but during double-sided printing, it is wise to check that
pages will bind properly---sometimes a printer will produce output in
which the even-numbered pages have a larger right-hand margin than the
odd-numbered pages.)
@end ignore

By default, nothing is specified for the footing of a Texinfo file,
so the footing remains blank.



@node Custom Headings
@nodedescription How to create your own headings and footings.
@subsection How to Make Your Own Headings

You can use the standard headings provided with Texinfo or specify
your own.  By default, Texinfo has no footers, so if you specify them,
the available page size for the main text will be slightly reduced.

Texinfo provides six commands for specifying headings and
footings:
@itemize @bullet
@item
@code{@@everyheading} and @code{@@everyfooting} generate page headers and
footers that are the same for both even- and odd-numbered pages.
@item
@code{@@evenheading} and @code{@@evenfooting} commands generate headers
and footers for even-numbered (left-hand) pages.
@item
@code{@@oddheading} and @code{@@oddfooting} generate headers and footers
for odd-numbered (right-hand) pages.
@end itemize

You must cancel the predefined heading commands with the
@code{@@headings off} command before defining your own specifications.

@need 1000
Here is how to place the chapter name at the left, the page number in
the center, and the date at the right of every header for both even-
and odd-numbered pages:

@example
@group
@@headings off
@@everyheading @@thischapter @@| @@thispage @@| @@today@{@}
@end group
@end example

@noindent
You need to divide the left part from the central part and the central
part from the right part by inserting @samp{@@|} between parts.
Otherwise, the specification command will not be able to tell where
the text for one part ends and the next part begins.

Each part can contain text or @@-commands.  The text is printed as if
the part were within an ordinary paragraph in the body of the page.
The @@-commands replace themselves with the page number, date, chapter
name, or whatever.

@need 950
Here are the six heading and footing commands:

@table @code
@findex everyheading
@findex everyfooting
@item @@everyheading @var{left} @@| @var{center} @@| @var{right}
@itemx @@everyfooting @var{left} @@| @var{center} @@| @var{right}
The `every' commands specify the format for both even- and odd-numbered
pages.  These commands are for documents that are printed on one side
of each sheet of paper, or for documents in which you want symmetrical
headers or footers.

@findex evenheading
@findex evenfooting
@findex oddheading
@findex oddfooting
@item @@evenheading @var{left} @@| @var{center} @@| @var{right}
@itemx @@oddheading  @var{left} @@| @var{center} @@| @var{right}
@itemx @@evenfooting @var{left} @@| @var{center} @@| @var{right}
@itemx @@oddfooting  @var{left} @@| @var{center} @@| @var{right}
The `even' and `odd' commands specify the format for even-numbered
pages and odd-numbered pages.  These commands are for books and
manuals that are printed on both sides of each sheet of paper.
@end table

Use the @samp{@@this@dots{}} series of @@-commands to
provide the names of chapters
and sections and the page number.  You can use the
@samp{@@this@dots{}} commands in the left, center, or right portions
of headers and footers.

@need 1000
Here are the @samp{@@this@dots{}} commands:

@table @code
@findex thispage
@item @@thispage
Expands to the current page number.

@findex thissection
@item @@thissection
Expands to the number and name of the current section, in the format
`Section 1.1: Title'.

@findex thissectionname
@item @@thissectionname
Expands to the name of the current section.

@findex thissectionnum
@item @@thissectionnum
Expands to the number of the current section, in the format `1.1'.

@findex thischapter
@item @@thischapter
Expands to the number and name of the current
chapter, in the format `Chapter 1: Title'.

@findex thischaptername
@item @@thischaptername
Expands to the name of the current chapter.

@findex thischapternum
@item @@thischapternum
Expands to the number of the current chapter, or letter of the current
appendix.

@findex thispart
@item @@thispart
Expands to the name of the current part, as specified by the last
@code{@@part} command.

@findex thistitle
@item @@thistitle
Expands to the name of the document, as specified by the
@code{@@settitle} command.

@findex thisfile
@item @@thisfile
For @code{@@include} files only: expands to the name of the current
@code{@@include} file.  If the current Texinfo source file is not an
@code{@@include} file, this command has no effect.  This command does
@emph{not} provide the name of the current Texinfo source file unless
it is an @code{@@include} file.  (@xref{Include Files}, for more
information about @code{@@include} files.)
@end table

@noindent
You can also use the @code{@@today@{@}} command, which expands to the
current date, in `1 Jan 1900' format.
@findex today

Other @@-commands and text are printed in a header or footer just as
if they were in the body of a page.  It is useful to incorporate text,
particularly when you are writing drafts:

@example
@group
@@headings off
@@everyheading @@emph@{Draft!@} @@| @@thispage @@| @@thischapter
@@everyfooting @@| @@| Version: 0.27: @@today@{@}
@end group
@end example

Beware of overlong titles: they may overlap another part of the
header or footer and blot it out.

If you have very short chapters and/or sections, several of them can
appear on a single page.  You can specify which chapters and sections
you want @code{@@thischapter}, @code{@@thissection} and other such
macros to refer to on such pages as follows:

@table @code
@findex everyheadingmarks
@findex everyfootingmarks
@item @@everyheadingmarks @var{ref}
@itemx @@everyfootingmarks @var{ref}
The @var{ref} argument can be either @code{top} (the @code{@@this...}
commands will refer to the chapter/section at the top of a page) or
@code{bottom} (the commands will reflect the situation at the bottom
of a page).  These @samp{@@every...} commands specify what to do on
both even- and odd-numbered pages.

@findex evenheadingmarks
@findex oddheadingmarks
@findex evenfootingmarks
@findex oddfootingmarks
@item @@evenheadingmarks @var{ref}
@itemx @@oddheadingmarks @var{ref}
@itemx @@evenfootingmarks @var{ref}
@itemx @@oddfootingmarks @var{ref}
These @samp{@@even...} and @samp{@@odd...} commands specify what to do
on only even- or odd-numbered pages, respectively.  The @var{ref}
argument is the same as with the @samp{@@every...} commands.
@end table

Write these commands immediately after the @code{@@...contents}
commands, or after the @code{@@end titlepage} command if you don't
have a table of contents or if it is printed at the end of your
manual.  These commands have no effect in @LaTeX{}.

By default, for @TeX{}, the @code{@@this...} commands reflect the situation at
the bottom of a page both in headings and in footings.


@node @code{@@paragraphindent}
@nodedescription Specify paragraph indentation.
@section @code{@@paragraphindent}: Controlling Paragraph Indentation

@anchor{paragraphindent}@c old name
@findex paragraphindent
@cindex Indenting paragraphs, control of
@cindex Paragraph indentation control

The Texinfo processors may insert whitespace at the beginning of the
first line of each paragraph, thereby indenting that paragraph.  You can
use the @code{@@paragraphindent} command to specify this indentation.
Write a @code{@@paragraphindent} command at the beginning of a line
followed by either @samp{asis} or a number:

@example
@@paragraphindent @var{indent}
@end example

The indentation is according to the value of @var{indent}:

@table @asis
@item @code{asis}
Do not change the existing indentation (not implemented in printed
output).

@item @code{none}
@itemx 0
Omit all indentation.

@item @var{n}
Indent by @var{n} space characters in Info output, by @var{n} ems in
printed output.

@end table

The default value of @var{indent} is 3.  @code{@@paragraphindent} is
ignored for HTML output.

It is best to write the @code{@@paragraphindent} command before the
end-of-header line at the beginning of a Texinfo file, so the region
formatting commands indent paragraphs as specified.  @xref{Start of
Header}.


@node @code{@@firstparagraphindent}
@nodedescription Suppressing first paragraph indentation.
@section @code{@@firstparagraphindent}: Indenting After Headings

@anchor{firstparagraphindent}@c old name
@findex firstparagraphindent
@cindex First paragraph, suppressing indentation of
@cindex Suppressing first paragraph indentation
@cindex Preventing first paragraph indentation
@cindex Indenting, suppressing of first paragraph
@cindex Headings, indentation after

As you can see in the present manual, the first paragraph in any
section is not indented by default.  Typographically, indentation is a
paragraph separator, which means that it is unnecessary when a new
section begins.  This indentation is controlled with the
@code{@@firstparagraphindent} command:

@example
@@firstparagraphindent @var{word}
@end example

The first paragraph after a heading is indented according to the value
of @var{word}:

@table @asis
@item @code{none}
Prevents the first paragraph from being indented (default).
This option is ignored by @command{makeinfo} if
@code{@@paragraphindent asis} is in effect.

@item @code{insert}
Include normal paragraph indentation.  This respects the paragraph
indentation set by a @code{@@paragraphindent} command
(@pxref{@code{@@paragraphindent}}).
@end table

@code{@@firstparagraphindent} is ignored for HTML and DocBook output.

It is best to write the @code{@@firstparagraphindent} command before the
end-of-header line at the beginning of a Texinfo file, so the region
formatting commands indent paragraphs as specified.  @xref{Start of
Header}.


@node @code{@@exampleindent}
@nodedescription Specify environment indentation.
@section @code{@@exampleindent}: Environment Indenting

@anchor{exampleindent}@c old name
@findex exampleindent
@cindex Indenting environments
@cindex Environment indentation
@cindex Example indentation

The Texinfo processors indent each line of @code{@@example} and similar
environments.  You can use the @code{@@exampleindent} command to specify
this indentation.  Write an @code{@@exampleindent} command at the
beginning of a line followed by either @samp{asis} or a number:

@example
@@exampleindent @var{indent}
@end example

The indentation is according to the value of @var{indent}:

@table @asis
@item @code{asis}
Do not change the existing indentation (not implemented in printed
output).

@item 0
Omit all indentation.

@item @var{n}
Indent environments by @var{n} space characters in Info output, by
@var{n} ems in printed output.

@end table

The default value of @var{indent} is 5 spaces in Info, and 0.4@dmn{in}
in printed output, which is somewhat less.  (The reduction is to help
fit more characters onto physical lines in printed manuals.)

It is best to write the @code{@@exampleindent} command before the
end-of-header line at the beginning of a Texinfo file, so the region
formatting commands indent paragraphs as specified.  @xref{Start of
Header}.


@node @code{@@smallbook}
@nodedescription How to print small format books and manuals.
@section @code{@@smallbook}: Printing ``Small'' Books

@anchor{smallbook}@c old name
@findex smallbook
@cindex Small book size
@cindex Book, printing small
@cindex Page sizes for books
@cindex Size of printed book

By default, @TeX{} typesets pages for printing in an 8.5 by 11 inch
format, which is the ``letter'' size commonly used in the United States.
However, you can direct @TeX{} or @LaTeX{} to typeset a document in a
7 by 9.25 inch format that is suitable for bound books by inserting the
following command on a line by itself at the beginning of the Texinfo file,
before the title page:

@example
@@smallbook
@end example

@noindent
(Since many books are about 7 by 9.25 inches, this command might better
have been called the @code{@@regularbooksize} command, but it came to be
called the @code{@@smallbook} command by comparison to the 8.5 by 11
inch format.)

@xref{Format with @command{texi2dvi} or @command{texi2pdf}},
and @ref{Preparing for @TeX{}}, for other ways to format with
@code{@@smallbook} with @TeX{} that do not require changing the source file.


@node A4 Paper
@nodedescription How to print on A4, A5 or B6 paper.
@section Printing on A4 Paper
@cindex A4 paper, printing on
@cindex Paper size, A4
@cindex European A4 paper
@findex afourpaper
You can format a document for printing on ISO 216 A4 paper size with
the @code{@@afourpaper} command.  Write the command on a line by
itself near the beginning of the Texinfo file, before the title page.

@cindex A5 paper, printing on
@findex afourlatex
@findex afourwide
@findex afivepaper
@findex bsixpaper
You may or may not prefer the formatting that results from the command
@code{@@afourlatex}.  There's also @code{@@afourwide} for A4 paper in
wide format, @code{@@afivepaper} for A5 paper, and @code{@@bsixpaper} for
B6 paper.

@xref{Format with @command{texi2dvi} or @command{texi2pdf}}
and @ref{Preparing for @TeX{}}, for other ways to format for different
paper sizes that do not require changing the source file.


@node @code{@@pagesizes}
@nodedescription How to print with customized page sizes.
@section @code{@@pagesizes} [@var{width}][, @var{height}]: Custom Page Sizes
@anchor{pagesizes}@c old node name

@findex pagesizes
@cindex Custom page sizes
@cindex Page sizes, customized
@cindex Text width and height
@cindex Width of text area
@cindex Height of text area
@cindex Depth of text area

You can explicitly specify the height and (optionally) width of the main
text area on the page with the @code{@@pagesizes} command.  Write this
on a line by itself near the beginning of the Texinfo file, before the
title page.  The height comes first, then the width if desired,
separated by a comma.  Examples:

@example
@@pagesizes 200mm,150mm  @c for b5 paper
@end example
@noindent and
@example
@@pagesizes 11.5in       @c for legal paper
@end example

@cindex B5 paper, printing on
@cindex Legal paper, printing on
This would be reasonable for printing on B5-size paper.  To emphasize,
this command specifies the size of the @emph{text area}, not the size of
the paper (which is 250@dmn{mm} by 177@dmn{mm} for B5, 14@dmn{in} by
8.5@dmn{in} for legal).

@cindex Margins on page, not controllable
To make more elaborate changes, such as changing any of the page
margins, you must define a new command in @file{texinfo.tex} or
@file{texinfo.cnf}.

@xref{Format with @command{texi2dvi} or @command{texi2pdf}},
and @ref{Preparing for @TeX{}}, for other ways to specify
@code{@@pagesizes} that do not require changing the source file.


@node Microtypography
@nodedescription Improving the appearance of paragraphs.
@section Microtypography

Some versions of @TeX{}, namely pdf@TeX{} and Lua@TeX{}, have
@dfn{microtypography} features.  These involve stretching font glyphs
slightly, and allowing text to produce very slightly into the margins.
Use of these gives @TeX{} more flexibility in breaking a paragraph
into lines, and can improve paragraph appearance by reducing hyphenation
and producing a more consistent typographic color.

@findex microtype
@file{texinfo.tex} uses these features (`microtype' for short) when
available.  You can turn microtype off by specifying @samp{@@microtype off}
in your input file; likewise, @samp{@@microtype on} turns microtype back on.

@cindex CM-Super fonts @subentry for @LaTeX{}
The fonts used in @LaTeX{} output may not be scalable.  If fonts are not
scalable, using microtypography could trigger an error when converting the
@LaTeX{} output.  Therefore microtypography is not turned on in the default
case in @LaTeX{} output.  It is possible to turn it on with @samp{@@microtype
on}.  A way to get scalable fonts for the font used in the default @LaTeX{}
output is to install the CM-Super font package
(@url{http://ctan.org/pkg/cm-super}).

The @code{@@microtype} command does nothing for other output formats.


@node Magnification
@nodedescription How to print scaled up output.
@section Magnification
@anchor{Cropmarks and Magnification} @c old name

@findex \mag @r{(raw @TeX{} magnification)}
@cindex Magnified printing
@cindex Larger or smaller pages
You can attempt to direct @TeX{} to typeset pages larger or smaller
than usual with the @code{\mag} @TeX{} command.  Everything that is
typeset is scaled proportionally larger or smaller.  (@code{\mag}
stands for ``magnification''.)  This is @emph{not} a Texinfo
@@-command, but is a raw @TeX{} command that is prefixed with a
backslash.  You have to write this command between @code{@@tex} and
@code{@@end tex} (@pxref{Raw Formatter Commands}).

Follow the @code{\mag} command with an @samp{=} and then a number that
is 1000 times the magnification you desire.  For example, to print pages
at 1.2 normal size, write the following near the beginning of the
Texinfo file, before the title page:

@example
@group
@@tex
\global\mag=1200
@@end tex
@end group
@end example

With some printing technologies, you can print normal-sized copies that
look better than usual by giving a larger-than-normal master to your
print shop.  They do the reduction, thus effectively increasing the
resolution.

Depending on your system, DVI files prepared with a
nonstandard-@code{\mag} may not print or may print only with certain
magnifications.  Be prepared to experiment.


@node Info Format Specification
@nodedescription Technical details of the Info file format.
@appendix Info Format Specification

@cindex Info format specification
@cindex Specification of Info format
@cindex Definition of Info format

Here we describe the technical details of the Info format.

In this formal description, the characters @code{<>*()|=#} are used
for the language of the description itself.  Other characters are
literal.  The formal constructs used are typical: @code{<...>}
indicates a metavariable name, @samp{=} means definition, @samp{*}
repetition, @samp{?} optional, @samp{()} grouping, @samp{|}
alternation, and @samp{#} comment.
@c Exception: @samp{*} at the beginning of a line is literal.
@c (Is it really worth stating this?)

In general, programs that read Info files should try to be
case-insensitive to keywords that occur in the file (for example,
@samp{Tag Table} and @samp{Tag table} should be equivalent) in order to
support Info-generating programs that use different capitalization.

We specify literal parentheses (those that are part of the Info
format) with @t{<lparen>} and @t{<rparen>}, meaning the single
characters @samp{(} and @samp{)} respectively.  Finally,
the two-character sequence @samp{^@var{x}} means the single
character @samp{CTRL-@var{x}}, for any @var{x}.

This format definition was written some 25 years after the Info format
was first devised.  So in the event of conflicts between this
definition and actual practice, practice wins.  It also assumes some
general knowledge of Texinfo; it is meant to be a guide for
implementors rather than a rigid technical standard.  We may refer
back to other parts of this manual for examples and definitions,
rather than redundantly spelling out every detail.

@menu
* Whole:           Info Format Whole Manual.
* Preamble:        Info Format Preamble.
* Indirect:        Info Format Indirect Table.
* Tag table:       Info Format Tag Table.
* Local variables: Info Format Local Variables.
* Regular nodes:   Info Format Regular Nodes.
* Menu:            Info Format Menu.
* Image:           Info Format Image.
* Printindex:      Info Format Printindex.
* Cross-Reference: Info Format Cross Reference.
@end menu


@node Info Format Whole Manual
@nodedescription Split vs.@: nonsplit manuals.
@section Info Format: A Whole Manual

@cindex Nonsplit manuals, Info format of
@cindex Split manuals, Info format of
@cindex Whole manual, in Info format

To begin, an Info manual is either @dfn{nonsplit} (contained wholly
within a single file) or @dfn{split} (across several files).

The syntax for a nonsplit manual is:

@example
    <nonsplit info file> =
<preamble>
<node>*
<tag table>?
<local variables>?
@end example

When split, there is a @dfn{main file}, which contains only pointers
to the nodes given in other @dfn{subfiles}.  The main file looks
like this:

@example
    <split info main file> =
<preamble>
<indirect table>
<tag table>
<local variables>?
@end example

The subfiles in a split manual have the following syntax:

@example
    <split info subfile> =
<preamble>
<node>*
@end example

Note that the tag table is not optional for split files, as it is used
with the indirect table to deduce which subfile a particular node is in.

Several of the sections in an Info file (such as nodes or tag tables) begin
with a sequence:

@example
    <separator> = (^L)?^_(^L)?^J
@end example

@noindent
That is, a @samp{CTRL-_} character followed by a newline, with optional
formfeed characters.



@node Info Format Preamble
@section Info Format: Preamble

@cindex Preamble, in Info format

The @t{<preamble>} is text at the beginning of all output files.
It is not intended to be visible by default in an Info viewer, but
may be displayed upon user request.

@example
    <preamble> =
<identification>       # "This is FILENAME, produced by ..."
<copying text>         # Expansion of @@copying text.
<dir entries>          # Derived from @@dircategory and @@direntry.
@end example

@noindent
These pieces are:

@table @t
@item <identification line>
An arbitrary string beginning the output file, followed by a blank
line.

@item <copying text>
The expansion of a @code{@@copying} environment, if the manual has
one (@pxref{@code{@@copying}}).

@item <dir entries>
The result of any @code{@@dircategory} and @code{@@direntry}
commands present in the manual (@pxref{Installing Dir Entries}).

@end table


@node Info Format Indirect Table
@section Info Format: Indirect Table

@cindex Indirect table, in Info format

@example
    <indirect table> =
<separator>
Indirect:
(<filename>: <bytepos>)*
@end example

The indirect table is written to the main file in the case of split
output only.  It specifies, as a decimal integer, the starting byte 
position (zero-based) that the first node of each subfile would have if 
the subfiles were concatenated together in order, not including the 
top-level file.  The first node of actual content is pointed to by the 
first entry.

As an example, suppose split output is generated for the GDB manual.
The top-level file @file{gdb.info} will contain something like this:

@example
<separator>
Indirect:
gdb.info-1: 1878
gdb.info-2: 295733
...
@end example

This tells Info viewers that the first node of the manual occurs at
byte 1878 of the file @file{gdb.info-1} (which would be after that file's
preamble.)  The first node in the @file{gdb.info-2} subfile would start at
byte 295733 if @file{gdb.info-2} were appended to @file{gdb.info-1},
including any preamble sections in both files.

Unfortunately, Info-creating programs such as @command{makeinfo} have not
always implemented these rules perfectly, due to various bugs and
oversights.  Therefore, robust Info viewers should fall back to
searching ``nearby'' the given position for a node, instead of
giving up immediately if the position is not exactly at a node beginning.


@node Info Format Tag Table
@section Info Format: Tag Table

@cindex Tag table, in Info format

@example
    <tag table> =
<separator>
Tag Table:
(<lparen>Indirect<rparen>)?
(Node|Ref): <nodeid>^?<bytepos>
<separator>
End Tag Table
@end example

The @samp{(Indirect)} line appears in the case of split output only.

The tag table specifies the starting byte position of each node and anchor
in the file.  In the case of split output, it is only written in the main
output file.

Each line defines an identifier as either an anchor or a node, as
specified.  For example, @samp{Node: Top^?1647} says that the node named
@samp{Top} starts at byte 1647 while @samp{Ref: Overview-Footnote-1^?30045}
says that the anchor named @samp{Overview-Footnote-1} starts at byte 30045.
It is an error to define the same identifier both ways.  

In the case of nonsplit output, the byte positions simply refer to the
location in the output file.  In the case of split output, the byte
positions refer to an imaginary file created by concatenating all the
split files (but not the top-level file).  See the previous section.

Here is an example:

@example
^_
Tag Table:
Node: Top^?89
Node: Ch1^?292
^_
End Tag Table
@end example

@noindent
This specifies a manual with two nodes, `Top' and `Ch1', at byte
positions 89 and 292 respectively.  Because the @samp{(Indirect)} line
is not present, the manual is not split.

Preamble sections or other non-node sections of files do not have a tag
table entry.


@node Info Format Local Variables
@section Info Format: Local Variables

@cindex Local variable section, in Info format

The local variables section is optional.  It is currently used to give
the encoding information and/or the document language code.

@example
    <local variables> =
<separator>
Local Variables:
(coding: <encoding>)?
(Info-documentlanguage: <language>)?
(Info-documentscript: <script>)?
(Info-documentlanguagevariant: <variant>(-<variant>)*)?
End:
@end example

@xref{@code{@@documentencoding}} for information about the document encoding.

@samp{<language>} should be of the form @var{ll} or @var{ll}_@var{cc}; see
@ref{@code{@@documentlanguage}}. @samp{<script>} document script
correspond to @code{@@documentscript} in Texinfo. The language variants
are separated by @samp{-}.   @xref{Setting the language}.
Only one language, script and variants list can be specified
in the local variables section even if the corresponding commands such as
@code{@@documentlanguage} occurs several times in a Texinfo document.


@node Info Format Regular Nodes
@section Info Format: Regular Nodes

@cindex Info nodes, in Info format

Regular nodes look like this:

@example
    <node> =
<separator>
File: <fn>, Node: <id1>, (Next: <id2>, )? (Prev: <id3>, )? Up: <id4>

<general text, until the next ^_ or end-of-file>
@end example

@noindent
At least one space or tab must be present after each colon and comma,
but any number of spaces are ignored.  The @t{<id>} node identifiers have
following format:

@example
   <id> = (<lparen><infofile><rparen>)?<node-spec>?
   <node-spec> = <nodename> | <del><nodename><del>
   <del> = ^?
@end example

This @t{<node>} defines @t{<id1>} in file @t{<fn>}, which is typically
either @samp{manualname} or @samp{manualname.info}.  No parenthesized
@t{<infofile>} component may appear within @t{<id1>}.

Each of the identifiers after @code{Next}, @code{Prev} and @code{Up}
refer to nodes or anchors within a file.  These pointers normally
refer within the same file, but @samp{(dir)} is often used to point to
the top-level dir file.  If an @t{<infofile>} component is used then
the node name may be omitted, in which case the node identifier refers
to the @samp{Top} node within the referenced file.

The @code{Next} and @code{Prev} pointers are optional.  The @code{Up}
pointer is technically also optional, although most likely this
indicates a mistake in the node structuring.  Conventionally, the
nodes are arranged to form a tree, but this is not a requirement of
the format.

Node names containing periods, commas, colons or parentheses can confuse Info
readers.  If it is necessary to refer to a node whose name contains any of
these, the @t{<nodename>} should be surrounded by a pair of @code{DEL}
characters (@samp{CTRL-?}, character number 127).  @command{makeinfo} adds
these characters when needed in the default case.  Note that not all Info
readers recognize this syntax.  @xref{Info Node Names Constraints}.

The @t{<general text>} of the node can include the special constructs
described next.


@node Info Format Menu
@section Info Format: Menu

@cindex Menus, in Info format

Conventionally menus appear at the end of nodes, but the Info format
places no restrictions on their location.

@example
    <menu> =
* Menu:
(<menu entry> | <menu comment>)*
@end example

The parts of a @t{<menu entry>} are also described in @ref{Menu
Parts}.  They have the same syntax as cross-references, with a leading @samp{*}
instead of @samp{* (N|n)ote} (@pxref{Info Format Cross Reference}).  Indices
extend the menu format to specify the destination line; @pxref{Info Format
Printindex}.

A @t{<menu comment>} is any line not beginning with @samp{*} that
appears either at the beginning of the menu or is separated from a
menu entry by one or more blank lines.  These comments are intended to
be displayed as part of the menu, as-is (@pxref{Writing a Menu}).


@node Info Format Image
@section Info Format: Image

@cindex Images @subentry in Info format

The @code{@@image} command results in the following special directive
within the Info file (@pxref{Images}):

@example
    <image> =
^@@^H[image src="<image file>"
            (dpi=<dpi>)?
            (depth=<depth>)?
            (text="<txt file contents>")?
            (alt="<alt text>")?
^@@^H]
@end example

The line breaks and indentation in this description are editorial; the
whitespace between the different parts of the directive in Info files
is arbitrary.

In the strings @t{<image file>}, @t{<txt file contents>} and @t{<alt
text>}, @samp{"} is quoted as @samp{\"} and @samp{\} is quoted as
@samp{\\}.  The txt and alt specifications are optional.

The @t{alt} value serves the same purpose as in HTML: A prose
description of the image.  In text-only displays or speech systems,
for example, the @t{alt} value may be used instead of displaying the
(typically graphical) @t{<image file>}.

The @t{<txt file contents>}, if present, should be taken as an ASCII
representation of the image, for possible use on a text-only display.

The format does not prescribe the choice between displaying the
@t{<image file>}, the @t{<alt text>} or the @t{<txt file contents>}.

The @t{dpi} and @t{depth} options are only output for the
experimental @samp{INFO_MATH_IMAGES} variable of @command{texi2any}
(@pxref{Info and Plaintext Customization Variables}).

@t{dpi} gives the dots-per-inch (@dfn{DPI}) of the image.  Info-viewing
programs could use this to scale the image so it is an appropriate size
for surrounding text.  Here is a possible formula for the height of
an image in pixels:

@displaymath
h_{@r{display}} = (h_{@r{file}} / dpi) * (72.27/10) * f
@end displaymath

@noindent Here, @math{h_{@r{display}}} is the height in pixels to display
the image at, @math{h_{@r{file}}} is the height in pixels of the unscaled
image, @math{dpi} is the DPI from the Info file, and @math{f} is
the font size in pizels of the currently used font.

The 72.27 in this formula is the number of points in an inch (as used
by @TeX{}).  The 10 is the default 10 @dmn{point} font size of @TeX{},
in other words, the size of 1 em.  The quotient (72.27/10) gives the
number of ems per inch and converts from the height of the image in
inches to the height of the image in ems.

@t{depth} gives the below-baseline depth of the image, in image pixels
(before scaling).  Viewing programs should use it for shifting
the image downwards to align it properly with surrounding text.


@node Info Format Printindex
@section Info Format: Printindex

@cindex Indices, in Info format

An index in Info format is a kind of menu, with an additional directive
at the beginning to mark it as an index menu.

@example
    <printindex> =
^@@^H[index^@@^H]
* Menu:

<index entry>*
@end example

The @t{<index entry>} items are similar to normal menu entries, but
the free-format description is replaced by the line number of where
the entries occurs in the text:

@example
    <index entry> =
* <entry text>: <node-spec>. <line-spec>

    <line-spec> =
<lparen>line <lineno><rparen>
@end example

@noindent

The initial part, @samp{<entry text>: <entry node>.}, should be on a
single line.  The @t{<entry text>} is the index term.

Even though @t{<entry text>} is followed by a colon, it may itself
contain colons, so Info readers should try to include as much of the
line as possible in the @t{<entry text>}.  (However, @t{<entry text>}
may not contain the @code{DEL} characters that may occur in @t{<node-spec>}.)

@t{<lineno>} is an unsigned integer, given relative to the start
of the @t{<entry node>}.  An optional line break may occur before
@samp{<line-spec>}.

Here is an example:

@example
^@@^H[index^@@^H]
* Menu:

* thunder:           Weather Phenomena.             (line 5)
@end example

This means that an index entry for `thunder' appears at line 5 of the
node `Weather Phenomena'.


@node Info Format Cross Reference
@section Info Format: Cross-reference

@cindex Cross-references, in Info format

A general cross-reference in Info format has one of the following two forms:

@example
    <cross-reference> =
  * (N|n)ote <id>::
@c| * (N|n)ote <label>:<id>(.|,)?
| * (N|n)ote <label>:<id>(.|,)

    <id> = (<lparen><infofile><rparen>)?<node-spec>?
    <label> = <label text> | <del><label text><del>
@end example

No space should occur between the @samp{*} character and the following
@samp{N} or @samp{n}.  @samp{*Note} should be used at the start of a
sentence, otherwise @samp{*note} should be used.  (Some Info readers,
such as the one in Emacs, can display @samp{*Note} and @samp{*note} as
@samp{See} and @samp{see} respectively.) In both cases, @t{<label
text>} is descriptive text.

In both forms the @t{<id>} refers to a node or anchor, in the same way
as a reference in the node information line does (@pxref{Info Format
Regular Nodes}).  The optional parenthesized @samp{<infofile>} is the
name of the manual being referenced, and @t{<node-spec>} gives the
node or anchor within that manual.

The second form has a descriptive label.  A cross-reference in this form
should usually be terminated with a comma or period, to make it
feasible to find the end of the @t{<id>}.

If @t{<label>} contains a colon character (@t{:}), it should be
surrounded with a pair of @t{<del>} characters.
Likewise, quoting characters may be used for the node
name if it contains problematic characters;
then a terminating comma or period is not needed.
As stated earlier, this quoting mechanism is not supported in all
Info-reading programs.

The format does not prescribe how to find other manuals to resolve
such references.

Here are some examples:

@example
*note GNU Free Documentation License::
*note Tag table: Info Format Tag Table, for details.
*Note Overview: (make)Top.
*Note ^?:^?: (bash)Bourne Shell Builtins.
*Note alloca.h: (gnulib)^?alloca.h^?.
@end example

The first shows a reference to a node in the current manual using the 
short form.

The second also refers to a node in the current manual, namely `Info
Format Tag Table'; the `Tag table' before the @samp{:} is only a label
on this particular reference, and the @samp{for details.} is text
belonging to the sentence, not part of the reference.

The third example refers to the node `Top' in another manual, namely
@samp{make}, with `Overview' being the label for this cross-reference.

The fourth example shows a colon character being quoted in a label,
and the fifth example shows a period being quoted in a node name.

@xref{Cross References}.


@node GNU Free Documentation License
@nodedescription Copying this manual.
@appendix GNU Free Documentation License

@include fdl.texi


@node Command Index
@unnumbered Command Index

This is an alphabetical list of all the @@-commands and assorted Emacs Lisp
functions.  To make the list easier to use, the commands are listed without
their preceding @samp{@@}.

@printindex fn


@node Variables Index
@unnumbered Variables Index

This is an alphabetical list of all variables, mainly customization variables.

@printindex vr


@node General Index
@nodedescription A menu covering many topics.
@unnumbered General Index

@printindex cp


@bye