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Add an example program.

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Michael Kerrisk 2007-06-30 13:03:08 +00:00
parent af4c9a828f
commit 6a2df4ee5e
1 changed files with 51 additions and 1 deletions
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52
man2/chown.2
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@ -1,7 +1,8 @@
.\" Hey Emacs! This file is -*- nroff -*- source.
.\"
.\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
.\" Copyright (c) 1998 Andries Brouwer (aeb@cwi.nl)
.\" and Copyright (c) 1998 Andries Brouwer (aeb@cwi.nl)
.\" and Copyright (c) 2007 Michael Kerrisk <mtk-manpages@gmx.net>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
@ -29,6 +30,7 @@
.\" Modified 1996-11-06 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 1997-05-18 by Michael Haardt <michael@cantor.informatik.rwth-aachen.de>
.\" Modified 2004-06-23 by Michael Kerrisk <mtk-manpages@gmx.net>
.\" 2007-07-08, mtk, added an example program; updated SYNOPSIS
.\"
.TH CHOWN 2 2007-07-08 "Linux" "Linux Programmer's Manual"
.SH NAME
@ -187,6 +189,54 @@ as the old
has got the same syscall number, and
.BR chown ()
got the newly introduced number.
.SH EXAMPLE
.PP
The following program changes the ownership of the file named in
its second command-line argument to the value specified in its
first command-line arguemnt.
The new owner can be specified either as a numeric user ID,
or as a username (which is converted to a user ID by using
.BR getpwnam (3)
to perform a lookup in the system password file).
.nf
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int
main(int argc, char *argv[])
{
uid_t uid;
struct passwd *pwd;
char *endptr;
if (argc != 3 || argv[1][0] == '\\0') {
fprintf(stderr, "%s <owner> <file>\\n", argv[0]);
exit(EXIT_FAILURE);
}
uid = strtol(argv[1], &endptr, 10); /* Allow a numeric string */
if (*endptr != '\\0') { /* Was not pure numeric string */
pwd = getpwnam(argv[1]); /* Try getting UID for username */
if (pwd == NULL) {
perror("getpwnam");
exit(EXIT_FAILURE);
}
uid = pwd\->pw_uid;
}
if (chown(argv[2], uid, \-1) == \-1) {
perror("chown");
exit(EXIT_FAILURE);
} /* if */
exit(EXIT_SUCCESS);
} /* main */
.fi
.SH "SEE ALSO"
.BR chmod (2),
.BR fchownat (2),