1ffdcdadf6
It shows the difference between getprogname() and argv[0]. Reviewed by: yuripv Approved by: yuripv (src) MFC after: 2 weeks Differential Revision: https://reviews.freebsd.org/D27204
121 lines
3.6 KiB
Groff
121 lines
3.6 KiB
Groff
.\"
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.\" Copyright (c) 2001 Christopher G. Demetriou
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed for the
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.\" NetBSD Project. See http://www.netbsd.org/ for
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.\" information about NetBSD.
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.\" 4. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd April 18, 2021
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.Dt GETPROGNAME 3
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.Os
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.Sh NAME
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.Nm getprogname ,
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.Nm setprogname
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.Nd get or set the program name
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdlib.h
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.Ft const char *
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.Fn getprogname "void"
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.Ft void
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.Fn setprogname "const char *progname"
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.Sh DESCRIPTION
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The
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.Fn getprogname
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and
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.Fn setprogname
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functions manipulate the name of the current program.
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They are used by error-reporting routines to produce
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consistent output.
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.Pp
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The
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.Fn getprogname
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function returns the name of the program.
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If the name has not been set yet, it will return
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.Dv NULL .
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.Pp
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The
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.Fn setprogname
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function sets the name of the program to be the last component of the
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.Fa progname
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argument.
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Since a pointer to the given string is kept as the program name,
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it should not be modified for the rest of the program's lifetime.
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.Pp
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In
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.Fx ,
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the name of the program is set by the start-up code that is run before
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.Fn main ;
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thus,
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running
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.Fn setprogname
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is not necessary.
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Programs that desire maximum portability should still call it;
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on another operating system,
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these functions may be implemented in a portability library.
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Calling
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.Fn setprogname
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allows the aforementioned library to learn the program name without
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modifications to the start-up code.
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.Sh EXAMPLES
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The following example presents a simple program, which shows the difference
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between
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.Fn getprogname
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and
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.Va "argv[0]" .
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.Bd -literal -offset indent
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#include <stdio.h>
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#include <stdlib.h>
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int
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main(int argc, char** argv)
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{
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printf("getprogname(): %s\en", getprogname());
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printf("argv[0]: %s\en", argv[0]);
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return (0);
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}
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.Ed
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.Pp
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When compiled and executed (e.g., with
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.Ql ./a.out )
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the output of the program is going to look like this:
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.Bd -literal -offset indent
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getprogname(): a.out
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argv[0]: ./a.out
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.Ed
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.Sh SEE ALSO
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.Xr err 3 ,
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.Xr setproctitle 3
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.Sh HISTORY
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These functions first appeared in
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.Nx 1.6 ,
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and made their way into
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.Fx 4.4 .
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