+/* Determine the session ID of the controlling terminal of the current process.
+ Copyright (C) 2010 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+
+#include <config.h>
+
+#define USE_OLD_TTY /* needed on OpenBSD 4.5, so that TIOCGSID gets defined */
+
+/* Specification. */
+#include <termios.h>
+
+#include <errno.h>
+#include <sys/ioctl.h>
+
+pid_t
+tcgetsid (int fd)
+{
+#ifdef TIOCGSID /* MacOS X, OpenBSD */
+ int sid;
+
+ if (ioctl (fd, TIOCGSID, &sid) < 0)
+ return -1; /* errno is set here */
+
+ return sid;
+#else /* FreeBSD, Cygwin, mingw */
+ errno = ENOSYS;
+ return -1;
+#endif
+}