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/* Copyright (C) 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
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 <alloca.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <utmp.h>
#include <sys/file.h>
int
pututline_r (const struct utmp *utmp_ptr, struct utmp_data *utmp_data)
{
/* Open utmp file if not already done. */
if (utmp_data->ut_fd == -1)
{
setutent_r (utmp_data);
if (utmp_data->ut_fd == -1)
return -1;
}
/* Seek position to write. */
if (utmp_data->ubuf.ut_type != utmp_ptr->ut_type)
{
/* We must not overwrite the data in UTMP_DATA. */
struct utmp_data *data_tmp = alloca (sizeof (utmp_data));
struct utmp *dummy;
*data_tmp = *utmp_data;
utmp_data = data_tmp;
if (getutid_r (utmp_ptr, &dummy, utmp_data) < 0)
{
if (errno != ESRCH)
return -1;
utmp_data->loc_utmp = lseek (utmp_data->ut_fd, 0, SEEK_END);
if (utmp_data->loc_utmp == -1)
return -1;
}
}
/* Position file correctly. */
if (utmp_data->loc_utmp > 0
&& lseek (utmp_data->ut_fd, utmp_data->loc_utmp - sizeof (struct utmp),
SEEK_SET) < 0)
return -1;
/* XXX An alternative solution would be to call an SUID root program
which write the new value. */
/* Try to lock the file. */
if (flock (utmp_data->ut_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. */
(void) flock (utmp_data->ut_fd, LOCK_EX | LOCK_NB);
}
/* Write the new data. */
if (write (utmp_data->ut_fd, &utmp_data->ubuf, sizeof (struct utmp))
!= sizeof (struct utmp))
return -1;
/* And unlock the file. */
(void) flock (utmp_data->ut_fd, LOCK_UN);
return 0;
}
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