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Linux 2.6 - man page for setpgid (linux section 2)

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);

       pid_t getpgrp(void);		    /* POSIX.1 version */
       pid_t getpgrp(pid_t pid);	    /* BSD version */

       int setpgrp(void);		    /* System V version */
       int setpgrp(pid_t pid, pid_t pgid);  /* BSD version */

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       getpgid():
	   _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
	   || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L

       setpgrp() (POSIX.1):
	   _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
	   _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

       setpgrp() (BSD), getpgrp() (BSD):
	   _BSD_SOURCE &&
	       ! (_POSIX_SOURCE || _POSIX_C_SOURCE || _XOPEN_SOURCE ||
		  _XOPEN_SOURCE_EXTENDED || _GNU_SOURCE || _SVID_SOURCE)

DESCRIPTION
       All  of	these interfaces are available on Linux, and are used for getting and setting the
       process group ID (PGID) of a process.  The preferred, POSIX.1-specified ways of doing this
       are:  getpgrp(void), for retrieving the calling process's PGID; and setpgid(), for setting
       a process's PGID.

       setpgid() sets the PGID of the process specified by pid to pgid.  If pid is zero, then the
       process	ID of the calling process is used.  If pgid is zero, then the PGID of the process
       specified by pid is made the same as its process ID.  If  setpgid()  is	used  to  move	a
       process	from  one process group to another (as is done by some shells when creating pipe-
       lines), both process groups must be part of the same session (see  setsid(2)  and  creden-
       tials(7)).   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.

       The POSIX.1 version of getpgrp(), which takes no arguments, returns the PGID of the  call-
       ing process.

       getpgid()  returns  the PGID of the process specified by pid.  If pid is zero, the process
       ID of the calling process is used.  (Retrieving the PGID of a process other than the call-
       er is rarely necessary, and the POSIX.1 getpgrp() is preferred for that task.)

       The System V-style setpgrp(), which takes no arguments, is equivalent to setpgid(0, 0).

       The  BSD-specific  setpgrp()  call,  which  takes arguments pid and pgid, is equivalent to
       setpgid(pid, pgid).

       The BSD-specific getpgrp() call, which takes a  single  pid  argument,  is  equivalent  to
       getpgid(pid).

RETURN VALUE
       On  success,  setpgid() and setpgrp() return zero.  On error, -1 is returned, and errno is
       set appropriately.

       The POSIX.1 getpgrp() always returns the PGID of the caller.

       getpgid(), and the BSD-specific getpgrp() return a process group on success.  On error, -1
       is returned, and errno is set appropriately.

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(),  setp-
	      grp()).

       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 ses-
	      sion leader (setpgid(), setpgrp()).

       ESRCH  For getpgid(): pid does not match any process.  For setpgid(): pid is not the call-
	      ing process and not a child of the calling process.

CONFORMING TO
       setpgid() and the version of getpgrp() with no arguments conform to POSIX.1-2001.

       POSIX.1-2001  also  specifies  getpgid()  and the version of setpgrp() that takes no argu-
       ments.  (POSIX.1-2008 marks this setpgrp() specification as obsolete.)

       The version of getpgrp() with one argument and the version of  setpgrp()  that  takes  two
       arguments derive from 4.2BSD, and are not specified by POSIX.1.

NOTES
       A child created via fork(2) inherits its parent's process group ID.  The PGID is preserved
       across an execve(2).

       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.

       A session can have a controlling terminal.  At any time, one (and only one) of the process
       groups in the session can be the foreground process group for the terminal; the	remaining
       process	groups	are in the background.	If a signal is generated from the terminal (e.g.,
       typing the interrupt key to generate SIGINT),  that  signal  is	sent  to  the  foreground
       process	group.	 (See  termios(3)  for a description of the characters that generate sig-
       nals.)  Only the foreground process group may read(2) from the terminal; if  a  background
       process group tries to read(2) from the terminal, then the group is sent a SIGTTIN signal,
       which suspends it.  The tcgetpgrp(3) and tcsetpgrp(3) functions are used  to  get/set  the
       foreground process group of the controlling terminal.

       The  setpgid()  and getpgrp() calls are used by programs such as bash(1) to create process
       groups in order to implement shell job control.

       If a session has a controlling terminal, and the CLOCAL flag for that terminal is not set,
       and  a  terminal  hangup occurs, then the session leader is sent a SIGHUP.  If the session
       leader exits, then a SIGHUP signal will also 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.  An orphaned
       process group is one in which the parent of every member of process group is either itself
       also  a	member of the process group or is a member of a process group in a different ses-
       sion (see also credentials(7)).

SEE ALSO
       getuid(2), setsid(2), tcgetpgrp(3), tcsetpgrp(3), termios(3), credentials(7)

COLOPHON
       This page is part of release 3.55 of the Linux man-pages project.  A  description  of  the
       project,     and    information	  about    reporting	bugs,	 can	be    found    at
       http://www.kernel.org/doc/man-pages/.

Linux					    2013-07-31				       SETPGID(2)


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