contrib/tar/lib/readutmp.c

   1 /* GNU's read utmp module.
   2    Copyright (C) 1992-2000 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 <stdio.h>
  23
  24 #include <sys/types.h>
  25 #include <sys/stat.h>
  26 #if defined(STDC_HEADERS) || defined(HAVE_STRING_H)
  27 # include <string.h>
  28 #else
  29 # include <strings.h>
  30 #endif /* STDC_HEADERS || HAVE_STRING_H */
  31
  32 #include "readutmp.h"
  33
  34 char *xmalloc ();
  35 char *realloc ();
  36
  37 /* Copy UT->ut_name into storage obtained from malloc.  Then remove any
  38    trailing spaces from the copy, NUL terminate it, and return the copy.  */
  39
  40 char *
  41 extract_trimmed_name (const STRUCT_UTMP *ut)
  42 {
  43   char *p, *trimmed_name;
  44
  45   trimmed_name = xmalloc (sizeof (UT_USER (ut)) + 1);
  46   strncpy (trimmed_name, UT_USER (ut), sizeof (UT_USER (ut)));
  47   /* Append a trailing space character.  Some systems pad names shorter than
  48      the maximum with spaces, others pad with NULs.  Remove any spaces.  */
  49   trimmed_name[sizeof (UT_USER (ut))] = ' ';
  50   p = strchr (trimmed_name, ' ');
  51   if (p != NULL)
  52     *p = '\0';
  53   return trimmed_name;
  54 }
  55
  56 /* Read the utmp entries corresponding to file FILENAME into freshly-
  57    malloc'd storage, set *UTMP_BUF to that pointer, set *N_ENTRIES to
  58    the number of entries, and return zero.  If there is any error,
  59    return non-zero and don't modify the parameters.  */
  60
  61 #ifdef UTMP_NAME_FUNCTION
  62
  63 int
  64 read_utmp (const char *filename, int *n_entries, STRUCT_UTMP **utmp_buf)
  65 {
  66   int n_read;
  67   STRUCT_UTMP *u;
  68   STRUCT_UTMP *utmp = NULL;
  69
  70   /* Ignore the return value for now.
  71      Solaris' utmpname returns 1 upon success -- which is contrary
  72      to what the GNU libc version does.  In addition, older GNU libc
  73      versions are actually void.   */
  74   UTMP_NAME_FUNCTION (filename);
  75
  76   SET_UTMP_ENT ();
  77
  78   n_read = 0;
  79   while ((u = GET_UTMP_ENT ()) != NULL)
  80     {
  81       ++n_read;
  82       utmp = (STRUCT_UTMP *) realloc (utmp, n_read * sizeof (STRUCT_UTMP));
  83       if (utmp == NULL)
  84         return 1;
  85       utmp[n_read - 1] = *u;
  86     }
  87
  88   END_UTMP_ENT ();
  89
  90   *n_entries = n_read;
  91   *utmp_buf = utmp;
  92
  93   return 0;
  94 }
  95
  96 #else
  97
  98 int
  99 read_utmp (const char *filename, int *n_entries, STRUCT_UTMP **utmp_buf)
 100 {
 101   FILE *utmp;
 102   struct stat file_stats;
 103   size_t n_read;
 104   size_t size;
 105   STRUCT_UTMP *buf;
 106
 107   utmp = fopen (filename, "r");
 108   if (utmp == NULL)
 109     return 1;
 110
 111   fstat (fileno (utmp), &file_stats);
 112   size = file_stats.st_size;
 113   if (size > 0)
 114     buf = (STRUCT_UTMP *) xmalloc (size);
 115   else
 116     {
 117       fclose (utmp);
 118       return 1;
 119     }
 120
 121   /* Use < instead of != in case the utmp just grew.  */
 122   n_read = fread (buf, 1, size, utmp);
 123   if (ferror (utmp) || fclose (utmp) == EOF
 124       || n_read < size)
 125     return 1;
 126
 127   *n_entries = size / sizeof (STRUCT_UTMP);
 128   *utmp_buf = buf;
 129
 130   return 0;
 131 }
 132
 133 #endif