getpgid

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.

       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 pro-
       cess 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
       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)