# HG changeset patch
# User Jim Meyering <jim@meyering.net>
# Date 925532036 0
# Node ID b0ce344d4fda37095890ad00fa0009822d230bef
# Parent  e182ba5dd68fdf5c2ebcb78852fc11ce239193a2
*** empty log message ***

diff --git a/lib/dup2.c b/lib/dup2.c
new file mode 100644
--- /dev/null
+++ b/lib/dup2.c
@@ -0,0 +1,66 @@
+/* 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
+}
diff --git a/m4/ChangeLog b/m4/ChangeLog
--- a/m4/ChangeLog
+++ b/m4/ChangeLog
@@ -1,3 +1,7 @@
+1999-04-30  Paul Eggert  <eggert@twinsun.com>
+
+	* jm-macros.m4 (AC_REPLACE_FUNCS): Add dup2.
+
 1999-04-20  Jim Meyering  <meyering@ascend.com>
 
 	* xstrtoumax.m4: Require jm_AC_TYPE_UNSIGNED_LONG_LONG.