fopen-safer.c revision b7f2b4d529ee03ee0e4172cc06e7cd973bd9bef5 
1/* Invoke fopen, but avoid some glitches.
2   Copyright (C) 2001, 2004, 2005 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
17
18/* Written by Paul Eggert.  */
19
20#ifdef HAVE_CONFIG_H
21# include <config.h>
22#endif
23
24#include "stdio-safer.h"
25
26#include <errno.h>
27#include <unistd.h>
28#include "unistd-safer.h"
29
30#ifndef STDERR_FILENO
31# define STDERR_FILENO 2
32#endif
33
34/* Like fopen, but do not return stdin, stdout, or stderr.  */
35
36FILE *
37fopen_safer (char const *file, char const *mode)
38{
39  FILE *fp = fopen (file, mode);
40
41  if (fp)
42    {
43      int fd = fileno (fp);
44
45      if (0 <= fd && fd <= STDERR_FILENO)
46	{
47	  int f = dup_safer (fd);
48
49	  if (f < 0)
50	    {
51	      int e = errno;
52	      fclose (fp);
53	      errno = e;
54	      return NULL;
55	    }
56
57	  if (fclose (fp) != 0
58	      || ! (fp = fdopen (f, mode)))
59	    {
60	      int e = errno;
61	      close (f);
62	      errno = e;
63	      return NULL;
64	    }
65	}
66    }
67
68  return fp;
69}
70