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.\" Copyright Michael Haardt (michael@cantor.informatik.rwth-aachen.de) Sat Aug 27 20:43:50 MET DST 1994
.\"
.\" 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'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, write to the Free
.\" Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
.\" USA.
.\"
.\" Modified Sun Sep 11 19:19:05 1994 <faith@cs.unc.edu>
.\" Modified Mon Mar 25 10:19:00 1996 <aeb@cwi.nl> (merged a few
.\" tiny changes from a man page by Charles Livingston).
.\" Modified Sun Jul 21 14:45:46 1996 <aeb@cwi.nl>
.\"
.TH SETSID 2 "Aug 27, 1994" "Linux 1.0.0" "Linux Programmer's Manual"
.SH NAME
setsid \- creates a session and sets the process group ID
.SH SYNOPSIS
.ad l
.B #include <unistd.h>
.sp
.B pid_t setsid(void);
.br
.ad b
.SH DESCRIPTION
\fBsetsid()\fP creates a new session if the calling process is not a
process group leader. The calling process is the leader of the new
session, the process group leader of the new process group, and has no
controlling tty. The process group ID and session ID of the calling
process are set to the PID of the calling process. The calling process
will be the only process in this new process group and in this new session.
.SH "RETURN VALUE"
The session ID of the calling process.
.SH ERRORS
On error, \-1 will be returned. The only error which can happen is
EPERM. It is returned when the process group ID of any process
equals the PID of the calling process. Thus, in particular,
.B setsid
fails if the calling process is already a process group leader.
.SH NOTES
A process group leader is a process with process group ID equal
to its PID. In order to be sure that
.B setsid
will succeed, fork and exit, and have the child do
.BR setsid().
.SH "CONFORMING TO"
POSIX, SVr4.
.SH "SEE ALSO"
.BR setpgid (2),
.BR setpgrp (2)
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