Yolinux.com

setpgid manpage

Search topic Section
Get manual page for the search topic
List all commands matching the search topic
List all topics in the manpage index

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 pro-
       cess 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 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 pro-
       cess 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() (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  dif-
	      ferent  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 inte-
       ger n larger than or equal to 500.

SEE ALSO
       getuid(2),  setsid(2),  tcgetpgrp(3),  tcsetpgrp(3),  termios(3),  fea-
       ture_test_macros(7)



Linux				  2003-01-20			    SETPGID(2)
YoLinux.com Home Page
YoLinux Tutorial Index
Privacy Policy | Advertise with us | Feedback Form |
Unauthorized copying or redistribution prohibited.
    Bookmark and Share