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| <title>Conditional Commands (GNU Texinfo 6.8dev)</title> |
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| <div class="section-level-extent" id="Conditional-Commands"> |
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| <p> |
| Next: <a href="Conditional-Not-Commands.html" accesskey="n" rel="next">Conditional Not Commands</a>, Up: <a href="Conditionals.html" accesskey="u" rel="up">Conditionally Visible Text</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Command-and-Variable-Index.html" title="Index" rel="index">Index</a>]</p> |
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| <h3 class="section" id="Conditional-Commands-1">15.1 Conditional Commands</h3> |
| |
| <p>Texinfo has an <code class="code">@if<var class="var">format</var></code> environment for each output |
| format, to allow conditional inclusion of text for a particular output |
| format. |
| </p> |
| <a class="index-entry-id" id="index-ifinfo"></a> |
| <p><code class="code">@ifinfo</code> begins segments of text that should be ignored by |
| TeX when it typesets the printed manual, and by <code class="command">makeinfo</code> |
| when not producing Info output. The segment of text appears only in |
| the Info file and, for historical compatibility, the plain text |
| output. |
| </p> |
| <a class="index-entry-id" id="index-ifdocbook"></a> |
| <a class="index-entry-id" id="index-ifhtml"></a> |
| <a class="index-entry-id" id="index-ifplaintext"></a> |
| <a class="index-entry-id" id="index-iftex"></a> |
| <a class="index-entry-id" id="index-ifxml"></a> |
| <p>The environments for the other formats are analogous: |
| </p> |
| <dl class="table"> |
| <dt><code class="code">@ifdocbook … @end ifdocbook</code></dt> |
| <dd><p>Text to appear only in the DocBook output. |
| </p> |
| </dd> |
| <dt><code class="code">@ifhtml … @end ifhtml</code></dt> |
| <dd><p>Text to appear only in the HTML output. |
| </p> |
| </dd> |
| <dt><code class="code">@ifplaintext … @end ifplaintext</code></dt> |
| <dd><p>Text to appear only in the plain text output. |
| </p> |
| </dd> |
| <dt><code class="code">@iftex … @end iftex</code></dt> |
| <dd><p>Text to appear only in the printed manual. |
| </p> |
| </dd> |
| <dt><code class="code">@ifxml … @end ifxml</code></dt> |
| <dd><p>Text to appear only in the XML output. |
| </p></dd> |
| </dl> |
| |
| <p>The <code class="code">@if…</code> and <code class="code">@end if…</code> 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. |
| </p> |
| <p>The <code class="code">@if…</code> constructs are intended to conditionalize |
| normal Texinfo source; see <a class="pxref" href="Raw-Formatter-Commands.html">Raw Formatter Commands</a>, for using |
| underlying format commands directly. |
| </p> |
| <p>Here is an example showing all these conditionals: |
| </p> |
| <div class="example"> |
| <pre class="example-preformatted">@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. |
| @end ifhtml |
| @ifplaintext |
| Whereas this text will only appear in plain text. |
| @end ifplaintext |
| @ifxml |
| Notwithstanding that this will only appear in XML. |
| @end ifxml |
| @ifdocbook |
| Nevertheless, this will only appear in DocBook. |
| @end ifdocbook |
| </pre></div> |
| |
| <p>The preceding example produces the following line: |
| </p> |
| <p>And this text will only appear in HTML. |
| </p> |
| <p>Notice that you only see one of the input lines, depending on which |
| version of the manual you are reading. |
| </p> |
| <a class="index-entry-id" id="index-errormsg"></a> |
| <p>In complex documents, you may want Texinfo to issue an error message |
| in some conditionals that should not ever be processed. The |
| <code class="code">@errormsg{<var class="var">text</var>}</code> command will do this; it takes one |
| argument, the text of the error message. |
| </p> |
| <p>We mention <code class="code">@errormsg{}</code> 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. |
| See <a class="xref" href="External-Macro-Processors.html">External Macro Processors: Line Directives</a>, for a caveat regarding the line |
| numbers which <code class="code">@errormsg</code> emits in TeX. |
| </p> |
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| <p> |
| Next: <a href="Conditional-Not-Commands.html">Conditional Not Commands</a>, Up: <a href="Conditionals.html">Conditionally Visible Text</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Command-and-Variable-Index.html" title="Index" rel="index">Index</a>]</p> |
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