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
33static int
34dupfd (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
50int
51dup2 (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}
62