login/getutline_r.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
  17 not, 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 <unistd.h>
  22 #include <utmp.h>
  23
  24
  25 /* For implementing this function we don't use the getutent_r function
  26    because we can avoid the reposition on every new entry this way.  */
  27 int
  28 getutline_r (const struct utmp *line, struct utmp **utmp,
  29              struct utmp_data *utmp_data)
  30 {
  31   /* Open utmp file if not already done.  */
  32   if (utmp_data->ut_fd == -1)
  33     {
  34       setutent_r (utmp_data);
  35       if (utmp_data->ut_fd == -1)
  36         return -1;
  37     }
  38
  39   /* Position file correctly.  */
  40   if (lseek (utmp_data->ut_fd, utmp_data->loc_utmp, SEEK_SET) == -1)
  41     return -1;
  42
  43   do
  44     {
  45       /* Read the next entry.  */
  46       if (read (utmp_data->ut_fd, &utmp_data->ubuf, sizeof (struct utmp))
  47           != sizeof (struct utmp))
  48         {
  49           errno = ESRCH;
  50           return -1;
  51         }
  52
  53       /* Update position pointer.  */
  54       utmp_data->loc_utmp += sizeof (struct utmp);
  55     }
  56   while (strncmp (line->ut_line, utmp_data->ubuf.ut_line,
  57                   sizeof line->ut_line));
  58
  59   *utmp = &utmp_data->ubuf;
  60
  61   return 0;
  62 }