View Source: setpgid(2) - Waikato Linux Users Group

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SETPGID
!!!SETPGID
NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
NOTES
SEE ALSO
----
!!NAME


setpgid, getpgid, setpgrp, getpgrp - set/get process group
!!SYNOPSIS


__#include __


__int setpgid(pid_t__ ''pid''__, pid_t__
''pgid''__);
pid_t getpgid(pid_t__ ''pid''__);
int setpgrp(void);
pid_t getpgrp(void);__
!!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.


In the Linux DLL 4.4.1 library, __setpgrp__ simply calls
__setpgid(0,0)__.


__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(4) 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


__EINVAL__


''pgid'' is less than 0.


__EPERM__


Various permission violations.


__ESRCH__


''pid'' does not match any process.
!!CONFORMING TO


The functions __setpgid__ and __getpgrp__ conform to
POSIX.1. The function __setpgrp__ is from BSD 4.2. The
function __getpgid__ conforms to SVr4.
!!NOTES


POSIX took __setpgid__ from the BSD function
__setpgrp__. Also SysV has a function with the same name,
but it is identical to setsid(2).
!!SEE ALSO


getuid(2), setsid(2), tcsetpgrp(3),
termios(4)
----
4 pages link to setpgid(2):
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Last edited on Tuesday, June 4, 2002 12:23:46 am by "perry"
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