getpgid(0)



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)

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