lib/open-safer.c

   1 /* Invoke open, but avoid some glitches.
   2
   3    Copyright (C) 2004 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 2, or (at your option)
   8    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, write to the Free Software Foundation,
  17    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  18
  19 /* Written by Paul Eggert.  */
  20
  21 #if HAVE_CONFIG_H
  22 # include <config.h>
  23 #endif
  24
  25 #include <fcntl-safer.h>
  26
  27 #include <unistd-safer.h>
  28
  29 #include <errno.h>
  30 #include <stdarg.h>
  31
  32 #if HAVE_FCNTL_H
  33 # include <fcntl.h>
  34 #endif
  35
  36 #if HAVE_UNISTD_H
  37 # include <unistd.h>
  38 #endif
  39 #ifndef STDERR_FILENO
  40 # define STDERR_FILENO 2
  41 #endif
  42
  43 /* Like open, but do not return STDIN_FILENO, STDOUT_FILENO, or
  44    STDERR_FILENO.  */
  45
  46 int
  47 open_safer (char const *file, int oflag, ...)
  48 {
  49   int fd;
  50   mode_t mode = 0;
  51
  52   if (oflag & O_CREAT)
  53     {
  54       va_list args;
  55       va_start (args, oflag);
  56       if (sizeof (int) <= sizeof (mode_t))
  57         mode = va_arg (args, mode_t);
  58       else
  59         mode = va_arg (args, int);
  60       va_end (args);
  61     }
  62
  63   fd = open (file, oflag, mode);
  64
  65   if (0 <= fd && fd <= STDERR_FILENO)
  66     {
  67       int f = dup_safer (fd);
  68       int e = errno;
  69       close (fd);
  70       errno = e;
  71       fd = f;
  72     }
  73
  74   return fd;
  75 }