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

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

NAME         top

       setpgid, getpgid, setpgrp, getpgrp - set/get process group

SYNOPSIS         top

       #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
               || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L

       setpgrp() (POSIX.1):
           _XOPEN_SOURCE >= 500
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* Glibc versions <= 2.19: */ _SVID_SOURCE

       setpgrp() (BSD), getpgrp() (BSD):
           [These are available only before glibc 2.19]
           _BSD_SOURCE &&
               ! (_POSIX_SOURCE || _POSIX_C_SOURCE || _XOPEN_SOURCE ||
                   _GNU_SOURCE || _SVID_SOURCE)

DESCRIPTION         top

       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 pipelines), both process groups must be part of the same
       session (see setsid(2) and credentials(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 calling 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 caller 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 a wrapper function that calls

           setpgid(pid, pgid)

       Since glibc 2.19, the BSD-specific setpgrp() function is no longer
       exposed by <unistd.h>; calls should be replaced with the setpgid()
       call shown above.

       The BSD-specific getpgrp() call, which takes a single pid argument,
       is a wrapper function that calls

           getpgid(pid)

       Since glibc 2.19, the BSD-specific getpgrp() function is no longer
       exposed by <unistd.h>; calls should be replaced with calls to the
       POSIX.1 getpgrp() which takes no arguments (if the intent is to
       obtain the caller's PGID), or with the getpgid() call shown above.

RETURN VALUE         top

       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         top

       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(), 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
              different 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 calling process and not a child of the calling
              process.

CONFORMING TO         top

       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 arguments.  (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         top

       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 signals.)  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 session (see also
       credentials(7)).

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 4.07 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

Linux                            2016-03-15                       SETPGID(2)