1/* Duplicate an open file descriptor to a specified file descriptor.
2
3   Copyright (C) 1999, 2004, 2005, 2006, 2007 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
18
19/* written by Paul Eggert */
20
21#include <config.h>
22
23/* Specification.  */
24#include <unistd.h>
25
26#include <errno.h>
27#include <fcntl.h>
28
29#ifndef F_DUPFD
30static int
31dupfd (int fd, int desired_fd)
32{
33  int duplicated_fd = dup (fd);
34  if (duplicated_fd < 0 || duplicated_fd == desired_fd)
35    return duplicated_fd;
36  else
37    {
38      int r = dupfd (fd, desired_fd);
39      int e = errno;
40      close (duplicated_fd);
41      errno = e;
42      return r;
43    }
44}
45#endif
46
47int
48dup2 (int fd, int desired_fd)
49{
50  if (fd == desired_fd)
51    return fd;
52  close (desired_fd);
53#ifdef F_DUPFD
54  return fcntl (fd, F_DUPFD, desired_fd);
55#else
56  return dupfd (fd, desired_fd);
57#endif
58}
59