path: root/man2/setpgid.2

.\" Copyright (c) 1983, 1991 Regents of the University of California.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)getpgrp.2	6.4 (Berkeley) 3/10/91
.\"
.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
.\" Modified 1995-04-15 by Michael Chastain <mec@shell.portal.com>:
.\"   Added 'getpgid'.
.\" Modified 1996-07-21 by Andries Brouwer <aeb@cwi.nl>
.\" Modified 1996-11-06 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 1999-09-02 by Michael Haardt <michael@moria.de>
.\" Modified 2002-01-18 by Michael Kerrisk <mtk16@ext.canterbury.ac.nz>
.\" Modified 2003-01-20 by Andries Brouwer <aeb@cwi.nl>
.\"
.TH SETPGID 2 2003-01-20 "Linux" "Linux Programmer's Manual"
.SH NAME
setpgid, getpgid, setpgrp, getpgrp \- set/get process group
.SH SYNOPSIS
.B #include <unistd.h>
.sp
.BI "int setpgid(pid_t " pid ", pid_t " pgid );
.br
.BI "pid_t getpgid(pid_t " pid );
.br
.B int setpgrp(void);
.br
.B pid_t getpgrp(void);
.SH DESCRIPTION
.B setpgid
sets the process group ID of the process specified by
.I pid
to
.IR pgid .
If
.I pid
is zero, the process ID of the current process is used.  If
.I pgid
is zero, the process ID of the process specified by
.I pid
is used.  If \fBsetpgid\fP is used to move a process from one process
group to another (as is done by some shells when creating pipelines),
both process groups must be part of the same session.  In this case,
the \fIpgid\fP specifies an existing process group to be joined and the
session ID of that group must match the session ID of the joining process.

.B getpgid
returns the process group ID of the process specified by
.IR pid .
If
.I pid
is zero, the process ID of the current process is used.

The call
.B setpgrp()
is equivalent to
.BR setpgid(0,0) .

Similarly,
.B getpgrp()
is equivalent to
.BR getpgid(0) .
Each process group is a member of a session and each process is a
member of the session of which its process group is a member.

Process groups are used for distribution of signals, and by terminals to
arbitrate requests for their input: Processes that have the same process
group as the terminal are foreground and may read, while others will
block with a signal if they attempt to read.
These calls are thus used by programs such as
.BR csh (1)
to create process groups in implementing job control.  The
.B TIOCGPGRP
and
.B TIOCSPGRP
calls described in
.BR termios (3)
are used to get/set the process group of the control terminal.

If a session has a controlling terminal, CLOCAL is not set and a hangup
occurs, then the session leader is sent a SIGHUP.  If the session leader
exits, the SIGHUP signal will be sent to each process in the foreground
process group of the controlling terminal.

If the exit of the process causes a process group to become orphaned,
and if any member of the newly-orphaned process group is stopped, then a
SIGHUP signal followed by a SIGCONT signal will be sent to each process
in the newly-orphaned process group.

.SH "RETURN VALUE"
On success,
.BR setpgid " and " setpgrp
return zero.  On error, \-1 is returned, and
.I errno
is set appropriately.

.B getpgid
returns a process group on success.
On error, \-1 is returned, and
.I errno
is set appropriately.

.B getpgrp
always returns the current process group.
.SH ERRORS
.TP
.B EACCES
An attempt was made to change the process group ID
of one of the children of the calling process and the child had
already performed an \fBexecve\fP
(\fBsetpgid\fP, \fBsetpgrp\fP).
.TP
.B EINVAL
.I pgid
is less than 0
(\fBsetpgid\fP, \fBsetpgrp\fP).
.TP
.B EPERM
An attempt was made to move a process into a process group in a 
different session, or to change the process 
group ID of one of the children of the calling process and the 
child was in a different session, or to change the process group ID of
a session leader
(\fBsetpgid\fP, \fBsetpgrp\fP).
.TP
.B ESRCH
For
.BR getpgid :
.I pid
does not match any process.
For
.BR setpgid :
.I pid
is not the current process and not a child of the current process.
.SH "CONFORMING TO"
The functions
.B setpgid
and
.B getpgrp
conform to POSIX.1.
The function
.B setpgrp
is from BSD 4.2.
The function
.B getpgid
conforms to SVr4.
.SH NOTES
POSIX took
.B setpgid
from the BSD function
.BR setpgrp .
Also SysV has a function with the same name, but it is identical to
.BR setsid (2).
.LP
To get the prototypes under glibc, define both _XOPEN_SOURCE and
_XOPEN_SOURCE_EXTENDED, or use "#define _XOPEN_SOURCE \fIn\fP"
for some integer \fIn\fP larger than or equal to 500.
.SH "SEE ALSO"
.BR getuid (2),
.BR setsid (2),
.BR tcgetpgrp (3),
.BR tcsetpgrp (3),
.BR termios (3)