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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 implement-
       ing job control.	  The  TIOCGPGRP  and  TIOCSPGRP  calls	 described  in
       termios(3)  are used to get/set the process group of the	control	termi-
       nal.

       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 per-
	      formed 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  dif-
	      ferent  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 inte-
       ger n larger than or equal to 500.

SEE ALSO
       getuid(2), setsid(2), tcsetpgrp(3), termios(3)

Linux				  1999-09-02			    SETPGID(2)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO

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