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
dupfd(int fd,int desired_fd)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
dup2(int fd,int desired_fd)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 }
62