SETPGID(2)						     Linux Programmer's Manual							SETPGID(2)

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);
       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(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

       EINVAL pgid is less than 0 (setpgid, setpgrp).

       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 (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  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).

       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), tcsetpgrp(3), termios(3)

Linux								    1999-09-02								SETPGID(2)