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Definition of updwtmp function.

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Ulrich Drepper 1997-08-08 00:27:32 +00:00
parent 4a5bd8f420
commit 655224ac2a
1 changed files with 69 additions and 0 deletions
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login/updwtmp.c Normal file
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/* Copyright (C) 1997 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Mark Kettenis <kettenis@phys.uva.nl>, 1997.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <utmp.h>
#include <sys/file.h>
#include <sys/stat.h>
#include "utmp-private.h"
void
updwtmp (const char *wtmp_file, const struct utmp *utmp)
{
struct stat st;
size_t written;
int fd;
/* Open WTMP file. */
fd = __open (wtmp_file, O_WRONLY | O_APPEND);
if (fd < 0)
return;
/* Try to lock the file. */
if (__flock (fd, LOCK_EX | LOCK_NB) < 0 && errno != ENOSYS)
{
/* Oh, oh. The file is already locked. Wait a bit and try again. */
sleep (1);
/* This time we ignore the error. */
__flock (fd, LOCK_EX | LOCK_NB);
}
/* Remember original size of log file: */
if (__fstat (fd, &st) < 0)
goto done;
/* Write the entry. If we can't write all the bytes, reset the file
size back to the original size. That way, no partial entries
will remain. */
written = __write (fd, utmp, sizeof (struct utmp));
if (written > 0 && written != sizeof (struct utmp))
ftruncate (fd, st.st_size);
done:
/* And unlock the file. */
__flock (fd, LOCK_UN);
/* Close WTMP file. */
__close (fd);
}