@node progname and getprogname
@section progname and getprogname

@c Copyright (C) 2007, 2009-2019 Free Software Foundation, Inc.

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

Gnulib has two modules for retrieving the name of the currently executing
program: @code{progname} and @code{getprogname}.

@findex progname
@vindex program_name
The @code{progname} module defines a variable @code{program_name}.
It contains the name of the currently executing program, on all platforms.
But it cannot be used implicitly:  It requires that every @code{main}
function be modified to invoke @code{set_program_name (argv[0])} as one
of its first actions.

@findex getprogname
The @code{getprogname} module defines a function @code{getprogname()}.
It returns the name of the currently executing program, on most platforms.
The advantage of this module is that it can be used without prior
initializations.  But it has limitations:  In some rare situations, it
cannot determine the name; then it returns @code{"?"} instead.  And on
some platforms, it returns a truncated program name.

@findex error
The @code{error} function uses the @code{getprogname} module.