@deftypefn Extension {struct pex_obj *} pex_init (int @var{flags}, const char *@var{pname}, const char *@var{tempbase})

Prepare to execute one or more programs, with standard output of each
program fed to standard input of the next.  This is a system
independent interface to execute a pipeline.

@var{flags} is a bitwise combination of the following:

@table @code

@vindex PEX_RECORD_TIMES
@item PEX_RECORD_TIMES
Record subprocess times if possible.

@vindex PEX_USE_PIPES
@item PEX_USE_PIPES
Use pipes for communication between processes, if possible.

@vindex PEX_SAVE_TEMPS
@item PEX_SAVE_TEMPS
Don't delete temporary files used for communication between
processes.

@end table

@var{pname} is the name of program to be executed, used in error
messages.  @var{tempbase} is a base name to use for any required
temporary files; it may be @code{NULL} to use a randomly chosen name.

@end deftypefn

@deftypefn Extension {const char *} pex_run (struct pex_obj *@var{obj}, int @var{flags}, const char *@var{executable}, char * const *@var{argv}, const char *@var{outname}, const char *@var{errname}, int *@var{err})

Execute one program in a pipeline.  On success this returns
@code{NULL}.  On failure it returns an error message, a statically
allocated string.

@var{obj} is returned by a previous call to @code{pex_init}.

@var{flags} is a bitwise combination of the following:

@table @code

@vindex PEX_LAST
@item PEX_LAST
This must be set on the last program in the pipeline.  In particular,
it should be set when executing a single program.  The standard output
of the program will be sent to @var{outname}, or, if @var{outname} is
@code{NULL}, to the standard output of the calling program.  Do @emph{not}
set this bit if you want to call @code{pex_read_output}
(described below).  After a call to @code{pex_run} with this bit set,
@var{pex_run} may no longer be called with the same @var{obj}.

@vindex PEX_SEARCH
@item PEX_SEARCH
Search for the program using the user's executable search path.

@vindex PEX_SUFFIX
@item PEX_SUFFIX
@var{outname} is a suffix.  See the description of @var{outname},
below.

@vindex PEX_STDERR_TO_STDOUT
@item PEX_STDERR_TO_STDOUT
Send the program's standard error to standard output, if possible.

@vindex PEX_BINARY_INPUT
@vindex PEX_BINARY_OUTPUT
@item PEX_BINARY_INPUT
@itemx PEX_BINARY_OUTPUT
The standard input (output) of the program should be read (written) in
binary mode rather than text mode.  These flags are ignored on systems
which do not distinguish binary mode and text mode, such as Unix.  For
proper behavior these flags should match appropriately---a call to
@code{pex_run} using @code{PEX_BINARY_OUTPUT} should be followed by a
call using @code{PEX_BINARY_INPUT}.
@end table

@var{executable} is the program to execute.  @var{argv} is the set of
arguments to pass to the program; normally @code{@var{argv}[0]} will
be a copy of @var{executable}.

@var{outname} is used to set the name of the file to use for standard
output.  There are two cases in which no output file will be used:

@enumerate
@item
if @code{PEX_LAST} is not set in @var{flags}, and @code{PEX_USE_PIPES}
was set in the call to @code{pex_init}, and the system supports pipes

@item
if @code{PEX_LAST} is set in @var{flags}, and @var{outname} is
@code{NULL}
@end enumerate

@noindent
Otherwise the code will use a file to hold standard
output.  If @code{PEX_LAST} is not set, this file is considered to be
a temporary file, and it will be removed when no longer needed, unless
@code{PEX_SAVE_TEMPS} was set in the call to @code{pex_init}.

There are two cases to consider when setting the name of the file to
hold standard output.

@enumerate
@item
@code{PEX_SUFFIX} is set in @var{flags}.  In this case
@var{outname} may not be @code{NULL}.  If the @var{tempbase} parameter
to @code{pex_init} was not @code{NULL}, then the output file name is
the concatenation of @var{tempbase} and @var{outname}.  If
@var{tempbase} was @code{NULL}, then the output file name is a random
file name ending in @var{outname}.

@item
@code{PEX_SUFFIX} was not set in @var{flags}.  In this
case, if @var{outname} is not @code{NULL}, it is used as the output
file name.  If @var{outname} is @code{NULL}, and @var{tempbase} was
not NULL, the output file name is randomly chosen using
@var{tempbase}.  Otherwise the output file name is chosen completely
at random.
@end enumerate

@var{errname} is the file name to use for standard error output.  If
it is @code{NULL}, standard error is the same as the caller's.
Otherwise, standard error is written to the named file.

On an error return, the code sets @code{*@var{err}} to an @code{errno}
value, or to 0 if there is no relevant @code{errno}.

@end deftypefn

@deftypefn Extension {FILE *} pex_read_output (struct pex_obj *@var{obj}, int @var{binary})

Returns a @code{FILE} pointer which may be used to read the standard
output of the last program in the pipeline.  When this is used,
@code{PEX_LAST} should not be used in a call to @code{pex_run}.  After
this is called, @code{pex_run} may no longer be called with the same
@var{obj}.  @var{binary} should be non-zero if the file should be
opened in binary mode.  Don't call @code{fclose} on the returned file;
it will be closed by @code{pex_free}.

@end deftypefn

@deftypefn Extension int pex_get_status (struct pex_obj *@var{obj}, int @var{count}, int *@var{vector})

Returns the exit status of all programs run using @var{obj}.
@var{count} is the number of results expected.  The results will be
placed into @var{vector}.  The results are in the order of the calls
to @code{pex_run}.  Returns 0 on error, 1 on success.

@end deftypefn

@deftypefn Extension int pex_get_times (struct pex_obj *@var{obj}, int @var{count}, struct pex_time *@var{vector})

Returns the process execution times of all programs run using
@var{obj}.  @var{count} is the number of results expected.  The
results will be placed into @var{vector}.  The results are in the
order of the calls to @code{pex_run}.  Returns 0 on error, 1 on
success.

@code{struct pex_time} has the following fields of the type
@code{unsigned long}: @code{user_seconds},
@code{user_microseconds}, @code{system_seconds},
@code{system_microseconds}.  On systems which do not support reporting
process times, all the fields will be set to @code{0}.

@end deftypefn

@deftypefn Extension void pex_free (struct pex_obj @var{obj})

Clean up and free all data associated with @var{obj}.

@end deftypefn

@deftypefn Extension {const char *} pex_one (int @var{flags}, const char *@var{executable}, char * const *@var{argv}, const char *@var{pname}, const char *@var{outname}, const char *@var{errname}, int *@var{status}, int *@var{err})

An interface to permit the easy execution of a
single program.  The return value and most of the parameters are as
for a call to @code{pex_run}.  @var{flags} is restricted to a
combination of @code{PEX_SEARCH}, @code{PEX_STDERR_TO_STDOUT}, and
@code{PEX_BINARY_OUTPUT}.  @var{outname} is interpreted as if
@code{PEX_LAST} were set.  On a successful return, @code{*@var{status}} will
be set to the exit status of the program.

@end deftypefn

@deftypefn Extension int pexecute (const char *@var{program}, char * const *@var{argv}, const char *@var{this_pname}, const char *@var{temp_base}, char **@var{errmsg_fmt}, char **@var{errmsg_arg}, int flags)

This is the old interface to execute one or more programs.  It is
still supported for compatibility purposes, but is no longer
documented.

@end deftypefn

@deftypefn Extension int pwait (int @var{pid}, int *@var{status}, int @var{flags})

Another part of the old execution interface.

@end deftypefn