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 #include <string.h>
  24
  25
  26 /* For implementing this function we don't use the getutent_r function
  27    because we can avoid the reposition on every new entry this way.  */
  28 int
  29 getutline_r (const struct utmp *line, struct utmp **utmp,
  30              struct utmp_data *utmp_data)
  31 {
  32   /* Open utmp file if not already done.  */
  33   if (utmp_data->ut_fd == -1)
  34     {
  35       setutent_r (utmp_data);
  36       if (utmp_data->ut_fd == -1)
  37         return -1;
  38     }
  39
  40   /* Position file correctly.  */
  41   if (lseek (utmp_data->ut_fd, utmp_data->loc_utmp, SEEK_SET) == -1)
  42     return -1;
  43
  44   do
  45     {
  46       /* Read the next entry.  */
  47       if (read (utmp_data->ut_fd, &utmp_data->ubuf, sizeof (struct utmp))
  48           != sizeof (struct utmp))
  49         {
  50           errno = ESRCH;
  51           return -1;
  52         }
  53
  54       /* Update position pointer.  */
  55       utmp_data->loc_utmp += sizeof (struct utmp);
  56     }
  57   while (strncmp (line->ut_line, utmp_data->ubuf.ut_line,
  58                   sizeof line->ut_line));
  59
  60   *utmp = &utmp_data->ubuf;
  61
  62   return 0;
  63 }