Section (1) setsid
setsid — run a program in a new session
setsid [options] program
a program in a new session. The command calls fork(2) if already a
process group leader. Otherwise, it executes a program in the
current process. This default behavior is possible to
override by the
Set the controlling terminal to the current one.
Always create a new process.
Wait for the execution of the program to end, and return the exit value of this program as the return value of setsid.
Display version information and exit.
Display help text and exit.
Rick Sladkey <[email protected]>
Section (2) setsid
setsid — creates a session and sets the process group ID
#include <sys/types.h> #include <unistd.h>
setsid() creates a new
session if the calling process is not a process group leader.
The calling process is the leader of the new session (i.e.,
its session ID is made the same as its process ID). The
calling process also becomes the process group leader of a
new process group in the session (i.e., its process group ID
is made the same as its process ID).
The calling process will be the only process in the new process group and in the new session.
Initially, the new session has no controlling terminal. For details of how a session acquires a controlling terminal, see credentials(7).
On success, the (new) session ID of the calling process is
returned. On error, (pid_t)
−1 is returned, and
errno is set to indicate the error.
The process group ID of any process equals the PID of the calling process. Thus, in particular,
setsid() fails if the calling process is already a process group leader.
A process group leader is a process whose process group ID
equals its PID. Disallowing a process group leader from
setsid() prevents the
possibility that a process group leader places itself in a
new session while other processes in the process group remain
in the original session; such a scenario would break the
strict two-level hierarchy of sessions and process groups. In
order to be sure that
will succeed, call fork(2) and have the parent
_exit(2), while the child
(which by definition can_zsingle_quotesz_t be a process group leader) calls
If a session has a controlling terminal, and the
CLOCAL flag for that terminal
is not set, and a terminal hangup occurs, then the session
leader is sent a
If a process that is a session leader terminates, then a
SIGHUP signal is sent to each
process in the foreground process group of the controlling
This page is part of release 4.16 of the Linux
man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
Copyright Michael Haardt (michaelcantor.informatik.rwth-aachen.de)
Sat Aug 27 20:43:50 MET DST 1994
and Copyright (C) 2014, Michael Kerrisk <mtk.manpagesgmail.com>
This is free documentation; 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 of
the License, or (at your option) any later version.
The GNU General Public License_zsingle_quotesz_s references to object code
and executables are to be interpreted as the output of any
document formatting or typesetting system, including
intermediate and printed output.
This manual 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 manual; if not, see
Modified Sun Sep 11 19:19:05 1994 <faithcs.unc.edu>
Modified Mon Mar 25 10:19:00 1996 <aebcwi.nl> (merged a few
tiny changes from a man page by Charles Livingston).
Modified Sun Jul 21 14:45:46 1996 <aebcwi.nl>