external/gpl2/xcvs/dist/lib/dup2.c

   1 /* Duplicate an open file descriptor to a specified file descriptor.
   2    Copyright (C) 1999, 2004 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 <errno.h>
  25
  26 #include <fcntl.h>
  27
  28 #if HAVE_UNISTD_H
  29 # include <unistd.h>
  30 #endif
  31
  32 #ifndef F_DUPFD
  33 static int
  34 dupfd (int fd, int desired_fd)
  35 {
  36   int duplicated_fd = dup (fd);
  37   if (duplicated_fd < 0 || duplicated_fd == desired_fd)
  38     return duplicated_fd;
  39   else
  40     {
  41       int r = dupfd (fd, desired_fd);
  42       int e = errno;
  43       close (duplicated_fd);
  44       errno = e;
  45       return r;
  46     }
  47 }
  48 #endif
  49
  50 int
  51 dup2 (int fd, int desired_fd)
  52 {
  53   if (fd == desired_fd)
  54     return fd;
  55   close (desired_fd);
  56 #ifdef F_DUPFD
  57   return fcntl (fd, F_DUPFD, desired_fd);
  58 #else
  59   return dupfd (fd, desired_fd);
  60 #endif
  61 }