lib/fopen-safer.c

   1 /* Invoke fopen, but avoid some glitches.
   2    Copyright (C) 2001 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 Paul Eggert.  */
  19
  20 #if HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 #if HAVE_UNISTD_H
  25 # include <unistd.h>
  26 #endif
  27 #include <unistd-safer.h>
  28
  29 #ifndef STDERR_FILENO
  30 # define STDERR_FILENO 2
  31 #endif
  32
  33 #include <errno.h>
  34 #ifndef errno
  35 extern int errno;
  36 #endif
  37
  38 #include <stdio.h>
  39 #include <stdio-safer.h>
  40
  41 /* Like fopen, but do not return stdin, stdout, or stderr.  */
  42
  43 FILE *
  44 fopen_safer (char const *file, char const *mode)
  45 {
  46   FILE *fp = fopen (file, mode);
  47
  48   if (fp)
  49     {
  50       int fd = fileno (fp);
  51
  52       if (0 <= fd && fd <= STDERR_FILENO)
  53         {
  54           int f = dup_safer (fd);
  55
  56           if (f < 0)
  57             {
  58               int e = errno;
  59               fclose (fp);
  60               errno = e;
  61               return NULL;
  62             }
  63
  64           if (fclose (fp) != 0
  65               || ! (fp = fdopen (f, mode)))
  66             {
  67               int e = errno;
  68               close (f);
  69               errno = e;
  70               return NULL;
  71             }
  72         }
  73     }
  74
  75   return fp;
  76 }