1  /* Invoke fopen, but avoid some glitches.
       2  
       3     Copyright (C) 2001, 2004-2006, 2009-2022 Free Software Foundation, Inc.
       4  
       5     This program is free software: you can redistribute it and/or modify
       6     it under the terms of the GNU General Public License as published by
       7     the Free Software Foundation, either version 3 of the License, or
       8     (at your option) any later version.
       9  
      10     This program is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      13     GNU General Public License for more details.
      14  
      15     You should have received a copy of the GNU General Public License
      16     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
      17  
      18  /* Written by Paul Eggert.  */
      19  
      20  #include <config.h>
      21  
      22  #include "stdio-safer.h"
      23  
      24  #include <errno.h>
      25  #include <unistd.h>
      26  #include "unistd-safer.h"
      27  
      28  /* Like fopen, but do not return stdin, stdout, or stderr.  */
      29  
      30  FILE *
      31  fopen_safer (char const *file, char const *mode)
      32  {
      33    FILE *fp = fopen (file, mode);
      34  
      35    if (fp)
      36      {
      37        int fd = fileno (fp);
      38  
      39        if (0 <= fd && fd <= STDERR_FILENO)
      40          {
      41            int f = dup_safer (fd);
      42  
      43            if (f < 0)
      44              {
      45                int e = errno;
      46                fclose (fp);
      47                errno = e;
      48                return NULL;
      49              }
      50  
      51            if (fclose (fp) != 0
      52                || ! (fp = fdopen (f, mode)))
      53              {
      54                int e = errno;
      55                close (f);
      56                errno = e;
      57                return NULL;
      58              }
      59          }
      60      }
      61  
      62    return fp;
      63  }