lib/dup-safer.c

   1 /* Invoke dup, 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 #include <errno.h>
  25 #ifndef errno
  26 extern int errno;
  27 #endif
  28
  29 #if HAVE_FCNTL_H
  30 # include <fcntl.h>
  31 #endif
  32
  33 #if HAVE_UNISTD_H
  34 # include <unistd.h>
  35 #endif
  36 #ifndef STDERR_FILENO
  37 # define STDERR_FILENO 2
  38 #endif
  39
  40 #include <unistd-safer.h>
  41
  42 /* Like dup, but do not return STDIN_FILENO, STDOUT_FILENO, or
  43    STDERR_FILENO.  */
  44
  45 int
  46 dup_safer (int fd)
  47 {
  48 #ifdef F_DUPFD
  49   return fcntl (fd, F_DUPFD, STDERR_FILENO + 1);
  50 #else
  51   int f = dup (fd);
  52   if (0 <= f && f <= STDERR_FILENO)
  53     {
  54       int f1 = dup_safer (f);
  55       int e = errno;
  56       close (f);
  57       errno = e;
  58       f = f1;
  59     }
  60   return f;
  61 #endif
  62 }