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 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 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