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 #include <sys/cdefs.h>
18 __RCSID("$NetBSD: dup2.c,v 1.2 2016/05/17 14:00:09 christos Exp $");
19
20
21 /* written by Paul Eggert */
22
23 #ifdef HAVE_CONFIG_H
24 # include <config.h>
25 #endif
26
27 #include <errno.h>
28
29 #include <fcntl.h>
30
31 #if HAVE_UNISTD_H
32 # include <unistd.h>
33 #endif
34
35 #ifndef F_DUPFD
36 static int
dupfd(int fd,int desired_fd)37 dupfd (int fd, int desired_fd)
38 {
39 int duplicated_fd = dup (fd);
40 if (duplicated_fd < 0 || duplicated_fd == desired_fd)
41 return duplicated_fd;
42 else
43 {
44 int r = dupfd (fd, desired_fd);
45 int e = errno;
46 close (duplicated_fd);
47 errno = e;
48 return r;
49 }
50 }
51 #endif
52
53 int
dup2(int fd,int desired_fd)54 dup2 (int fd, int desired_fd)
55 {
56 if (fd == desired_fd)
57 return fd;
58 close (desired_fd);
59 #ifdef F_DUPFD
60 return fcntl (fd, F_DUPFD, desired_fd);
61 #else
62 return dupfd (fd, desired_fd);
63 #endif
64 }
65