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SETPGID(2)

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NAME    [Toc]    [Back]

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

SYNOPSIS    [Toc]    [Back]

       #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    [Toc]    [Back]

       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
       process 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
       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 implementing
 job control.   The  TIOCGPGRP  and  TIOCSPGRP  calls  described  in
       termios(4)  are used to get/set the process group of the control terminal.


       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
       process in the newly-orphaned process group.

RETURN VALUE    [Toc]    [Back]

       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    [Toc]    [Back]

       EINVAL pgid is less than 0.

       EPERM  Various permission violations.

       ESRCH  pid does not match any process.

CONFORMING TO    [Toc]    [Back]

       The functions setpgid and getpgrp conform  to  POSIX.1.	 The  function
       setpgrp is from BSD 4.2.  The function getpgid conforms to SVr4.

NOTES    [Toc]    [Back]

       POSIX  took  setpgid  from  the	BSD function setpgrp.  Also SysV has a
       function with the same name, but it is identical to setsid(2).

SEE ALSO    [Toc]    [Back]

      
      
       getuid(2), setsid(2), tcsetpgrp(3), termios(4)



Linux				  1999-09-02			    SETPGID(2)
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