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 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 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