login/logwtmp.c

   1 /* Copyright (C) 1996 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <string.h>
  22 #include <unistd.h>
  23 #include <utmp.h>
  24 #include <sys/file.h>
  25 #include <sys/stat.h>
  26
  27 void
  28 logwtmp (const char *line, const char *name, const char *host)
  29 {
  30   struct utmp ut;
  31   struct stat st;
  32   size_t written;
  33   int fd;
  34
  35   /* Open WTMP file.  */
  36   fd = __open (_PATH_WTMP, O_WRONLY | O_APPEND);
  37   if (fd < 0)
  38       return;
  39
  40   /* Set information in new entry.  */
  41   memset (&ut, 0, sizeof (ut));
  42 #if _HAVE_UT_PID - 0
  43   ut.ut_pid = getpid ();
  44 #endif
  45 #if _HAVE_UT_TYPE - 0
  46   ut.ut_type = name[0] ? USER_PROCESS : DEAD_PROCESS;
  47 #endif
  48   strncpy (ut.ut_line, line, sizeof ut.ut_line);
  49   strncpy (ut.ut_name, name, sizeof ut.ut_name);
  50 #if _HAVE_UT_HOST - 0
  51   strncpy (ut.ut_host, host, sizeof ut.ut_host);
  52 #endif
  53
  54 #if _HAVE_UT_TV - 0
  55   __gettimeofday (&ut.ut_tv, NULL);
  56 #else
  57   time (&ut.ut_time);
  58 #endif
  59
  60   /* Try to lock the file.  */
  61   if (__flock (fd, LOCK_EX | LOCK_NB) < 0 && errno != ENOSYS)
  62     {
  63       /* Oh, oh.  The file is already locked.  Wait a bit and try again.  */
  64       sleep (1);
  65
  66       /* This time we ignore the error.  */
  67       __flock (fd, LOCK_EX | LOCK_NB);
  68     }
  69
  70   /* Remember original size of log file: */
  71   if (__fstat (fd, &st) < 0)
  72     goto done;
  73
  74   /* Write the entry.  If we can't write all the bytes, reset the file
  75      size back to the original size.  That way, no partial entries
  76      will remain.  */
  77   written = __write (fd, &ut, sizeof (ut));
  78   if (written > 0 && written != sizeof (ut))
  79     ftruncate (fd, st.st_size);
  80
  81 done:
  82   /* And unlock the file.  */
  83   __flock (fd, LOCK_UN);
  84
  85   /* Close WTMP file.  */
  86   __close (fd);
  87 }