fopen-safer.c revision 98038 
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
35extern 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
43FILE *
44fopen_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}
77