lib/readutmp.c

   1 /* GNU's read utmp module.
   2    Copyright (C) 92, 93, 94, 95, 96, 1997 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 /* Written by jla; revised by djm */
  19
  20 #include <config.h>
  21
  22 #include <sys/stat.h>
  23 #if defined(STDC_HEADERS) || defined(HAVE_STRING_H)
  24 # include <string.h>
  25 #else
  26 # include <strings.h>
  27 #endif /* STDC_HEADERS || HAVE_STRING_H */
  28
  29 #include "readutmp.h"
  30
  31 char *xmalloc ();
  32
  33 /* Copy UT->ut_name into storage obtained from malloc.  Then remove any
  34    trailing spaces from the copy, NUL terminate it, and return the copy.  */
  35
  36 char *
  37 extract_trimmed_name (ut)
  38   const STRUCT_UTMP *ut;
  39 {
  40   char *p, *trimmed_name;
  41
  42   trimmed_name = xmalloc (sizeof (ut->ut_name) + 1);
  43   strncpy (trimmed_name, ut->ut_name, sizeof (ut->ut_name));
  44   /* Append a trailing space character.  Some systems pad names shorter than
  45      the maximum with spaces, others pad with NULs.  Remove any spaces.  */
  46   trimmed_name[sizeof (ut->ut_name)] = ' ';
  47   p = strchr (trimmed_name, ' ');
  48   if (p != NULL)
  49     *p = '\0';
  50   return trimmed_name;
  51 }
  52
  53 /* Read the utmp file FILENAME into *UTMP_BUF, set *N_ENTRIES to the
  54    number of entries read, and return zero.  If there is any error,
  55    return non-zero and don't modify the parameters.  */
  56
  57 int
  58 read_utmp (filename, n_entries, utmp_buf)
  59   const char *filename;
  60   int *n_entries;
  61   STRUCT_UTMP **utmp_buf;
  62 {
  63   FILE *utmp;
  64   struct stat file_stats;
  65   size_t n_read;
  66   size_t size;
  67   STRUCT_UTMP *buf;
  68
  69   utmp = fopen (filename, "r");
  70   if (utmp == NULL)
  71     return 1;
  72
  73   fstat (fileno (utmp), &file_stats);
  74   size = file_stats.st_size;
  75   if (size > 0)
  76     buf = (STRUCT_UTMP *) xmalloc (size);
  77   else
  78     {
  79       fclose (utmp);
  80       return 1;
  81     }
  82
  83   /* Use < instead of != in case the utmp just grew.  */
  84   n_read = fread (buf, 1, size, utmp);
  85   if (ferror (utmp) || fclose (utmp) == EOF
  86       || n_read < size)
  87     return 1;
  88
  89   *n_entries = size / sizeof (STRUCT_UTMP);
  90   *utmp_buf = buf;
  91
  92   return 0;
  93 }