mirror of https://github.com/mkerrisk/man-pages
88 lines
2.7 KiB
Groff
88 lines
2.7 KiB
Groff
.\" Copyright Michael Haardt (michael@cantor.informatik.rwth-aachen.de)
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.\" Sat Aug 27 20:43:50 MET DST 1994
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.\"
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, write to the Free
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.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
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.\" USA.
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.\"
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.\" Modified Sun Sep 11 19:19:05 1994 <faith@cs.unc.edu>
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.\" Modified Mon Mar 25 10:19:00 1996 <aeb@cwi.nl> (merged a few
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.\" tiny changes from a man page by Charles Livingston).
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.\" Modified Sun Jul 21 14:45:46 1996 <aeb@cwi.nl>
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.\"
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.TH SETSID 2 1994-08-27 "Linux" "Linux Programmer's Manual"
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.SH NAME
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setsid \- creates a session and sets the process group ID
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.SH SYNOPSIS
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.ad l
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.B #include <unistd.h>
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.sp
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.B pid_t setsid(void);
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.br
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.ad b
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.SH DESCRIPTION
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.BR setsid ()
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creates a new session if the calling process is not a
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process group leader.
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The calling process is the leader of the new
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session, the process group leader of the new process group, and has no
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controlling tty.
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The process group ID and session ID of the calling
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process are set to the PID of the calling process.
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The calling process will be the only process in
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this new process group and in this new session.
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.SH "RETURN VALUE"
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The session ID of the calling process.
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.SH ERRORS
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On error, \-1 is returned, and
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.I errno
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is set.
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The only error which can happen is
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.BR EPERM .
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It is returned when the process group ID of any process
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equals the PID of the calling process.
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Thus, in particular,
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.BR setsid ()
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fails if the calling process is already a process group leader.
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.SH "CONFORMING TO"
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SVr4, POSIX.1-2001.
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.SH NOTES
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A child created via
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.BR fork (2)
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inherits its parent's session ID.
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The session ID is preserved across an
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.BR execve (2).
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A process group leader is a process with process group ID equal
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to its PID.
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In order to be sure that
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.BR setsid ()
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will succeed,
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.BR fork (2)
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and
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.BR _exit (2),
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and have the child do
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.BR setsid ().
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.SH "SEE ALSO"
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.BR getsid (2),
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.BR setpgid (2),
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.BR setpgrp (2),
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.BR tcgetsid (3),
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.BR credentials (7)
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