+@c safe-ctype.c:25
+@defvr Extension HOST_CHARSET
+This macro indicates the basic character set and encoding used by the
+host: more precisely, the encoding used for character constants in
+preprocessor @samp{#if} statements (the C "execution character set").
+It is defined by @file{safe-ctype.h}, and will be an integer constant
+with one of the following values:
+
+@ftable @code
+@item HOST_CHARSET_UNKNOWN
+The host character set is unknown - that is, not one of the next two
+possibilities.
+
+@item HOST_CHARSET_ASCII
+The host character set is ASCII.
+
+@item HOST_CHARSET_EBCDIC
+The host character set is some variant of EBCDIC. (Only one of the
+nineteen EBCDIC varying characters is tested; exercise caution.)
+@end ftable
+@end defvr
+
+@c pexecute.txh:1
+@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
+
+@c pexecute.txh:161
+@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 @code{pex_init} 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, *@var{status} will
+be set to the exit status of the program.
+
+@end deftypefn
+
+@c pexecute.txh:32
+@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. This
+should not be set 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: 1)
+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;
+2) if @code{PEX_LAST} is set in @var{flags}, and @var{outname} is
+@code{NULL}. 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.
+
+First case: @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}.
+
+Second case: @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.
+
+@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.
+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
+