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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>
#include <sys/stat.h>
/* XXX An alternative solution would be to call a SUID root program
which write the new value. */
int
pututline_r (const struct utmp *id, struct utmp_data *utmp_data)
{
struct stat st;
int result = 0;
#if _HAVE_UT_TYPE - 0
/* Test whether ID has any of the legal types because we have to
prevent illegal entries. */
if (id->ut_type != RUN_LVL && id->ut_type != BOOT_TIME
&& id->ut_type != OLD_TIME && id->ut_type != NEW_TIME
&& id->ut_type != INIT_PROCESS && id->ut_type != LOGIN_PROCESS
&& id->ut_type != USER_PROCESS && id->ut_type != DEAD_PROCESS)
/* No, using '<' and '>' for the test is not possible. */
{
errno = EINVAL;
return -1;
}
#endif
/* 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;
}
#if _HAVE_UT_ID - 0
/* Check whether we need to reposition. Repositioning is necessary
either if the data in UTMP_DATA is not valid or if the ids don't
match: */
if (id->ut_id[0]
&& (utmp_data->loc_utmp < (off_t) sizeof (struct utmp)
|| strncmp(utmp_data->ubuf.ut_id, id->ut_id, sizeof (id->ut_id)) != 0))
{
/* We must not overwrite the data in UTMP_DATA since ID may be
aliasing it. */
struct utmp_data *data_tmp = alloca (sizeof (*data_tmp));
struct utmp *dummy;
*data_tmp = *utmp_data;
utmp_data = data_tmp;
if (getutid_r (id, &dummy, utmp_data) < 0)
{
if (errno != ESRCH)
/* Some error occured. If no entry was found, the position
pointer now is at the end of the file. */
return -1;
/* Set position pointer to position behind the record. */
utmp_data->loc_utmp += sizeof (struct utmp);
}
}
#endif
/* 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);
}
/* Find out how large the file is. */
result = fstat (utmp_data->ut_fd, &st);
if (result >= 0)
/* Position file correctly. */
if (utmp_data->loc_utmp < (off_t) sizeof (struct utmp))
/* Not located at any valid entry. Add at the end. */
{
result = lseek (utmp_data->ut_fd, 0L, SEEK_END);
if (result >= 0)
/* Where we'll be if the write succeeds. */
utmp_data->loc_utmp = st.st_size + sizeof (struct utmp);
}
else if (utmp_data->loc_utmp <= st.st_size)
result =
lseek (utmp_data->ut_fd, utmp_data->loc_utmp - sizeof (struct utmp),
SEEK_SET);
if (result >= 0)
/* Write the new data. */
if (write (utmp_data->ut_fd, id, sizeof (struct utmp))
!= sizeof (struct utmp))
{
/* If we appended a new record this is only partially written.
Remove it. */
if (utmp_data->loc_utmp > st.st_size)
{
(void) ftruncate (utmp_data->ut_fd, st.st_size);
utmp_data->loc_utmp = st.st_size;
}
result = -1;
}
/* And unlock the file. */
(void) flock (utmp_data->ut_fd, LOCK_UN);
return result;
}
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