--- /dev/null
+/* Duplicate an open file descriptor to a specified file descriptor.
+ Copyright 1999 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2, or (at your option)
+ any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software Foundation,
+ Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+
+/* written by Paul Eggert */
+
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <errno.h>
+#ifndef errno
+extern int errno;
+#endif
+
+#if HAVE_FCNTL_H
+# include <fcntl.h>
+#endif
+
+#if HAVE_UNISTD_H
+# include <unistd.h>
+#endif
+
+#ifndef F_DUPFD
+static int
+dupfd (int fd, int desired_fd)
+{
+ int duplicated_fd = dup (fd);
+ if (duplicated_fd < 0 || duplicated_fd == desired_fd)
+ return duplicated_fd;
+ else
+ {
+ int r = dupfd (fd, desired_fd);
+ int e = errno;
+ close (duplicated_fd);
+ errno = e;
+ return r;
+ }
+}
+#endif
+
+int
+dup2 (int fd, int desired_fd)
+{
+ if (fd == desired_fd)
+ return fd;
+ close (desired_fd);
+#ifdef F_DUPFD
+ return fcntl (fd, F_DUPFD, desired_fd);
+#else
+ return dupfd (fd, desired_fd);
+#endif
+}