Name
setpgid, getpgid, setpgrp, getpgrp — set/get process
group
Synopsis
#include <unistd.h>
int
setpgid( |
pid_t |
pid, |
| |
pid_t |
pgid); |
pid_t
getpgid( |
pid_t |
pid); |
DESCRIPTION
setpgid() sets the process
group ID of the process specified by pid to pgid. If pid is zero, the process ID of
the current process is used. If pgid is zero, the process ID of
the process specified by pid is used. If setpgid() 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 pgid specifies an existing
process group to be joined and the session ID of that group
must match the session ID of the joining process.
getpgid() returns the
process group ID of the process specified by pid. If pid is zero, the process ID of
the current process is used.
The call setpgrp() is
equivalent to setpgid(0,0).
Similarly, getpgrp() is
equivalent to 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 csh(1) to create process groups
in implementing job control. The TIOCGPGRP and TIOCSPGRP calls described in 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.
RETURN VALUE
On success, setpgid() and
setpgrp() return zero. On
error, −1 is returned, and errno is set appropriately.
getpgid() returns a process
group on success. On error, −1 is returned, and
errno is set appropriately.
getpgrp() always returns the
current process group.
ERRORS
- 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 execve(2)
(setpgid(), setpgrp()).
- EINVAL
-
pgid is less
than 0 (setpgid(),
setpgrp()).
- 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 (setpgid(), setpgrp()).
- ESRCH
-
For getpgid():
pid does not
match any process. For setpgid(): pid is not the current
process and not a child of the current process.
CONFORMING TO
The functions setpgid() and
getpgrp() conform to
POSIX.1-2001. The function setpgrp() is from 4.2BSD. The function
getpgid() conforms to SVr4.
NOTES
A child created via fork(2) inherits its
parent's process group ID. The process group ID is preserved
across an execve(2).
POSIX took setpgid() from
the BSD function setpgrp().
Also System V has a function with the same name, but it is
identical to setsid(2).
To get the prototypes under glibc, define both
_XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED, or use "#define
_XOPEN_SOURCE n"
for some integer n
larger than or equal to 500.
SEE ALSO
getuid(2), setsid(2), tcgetpgrp(3), tcsetpgrp(3), termios(3), feature_test_macros(7)
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 <mtk-manpages@gmx.net>
Modified 2003-01-20 by Andries Brouwer <aeb@cwi.nl>
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