NAME

     setsid - creates a session and sets the process group ID


SYNOPSIS

     #include <unistd.h>

     pid_t setsid(void);


DESCRIPTION

     setsid() creates a new session if the calling process is not
     a  process  group leader.  The calling process is the leader
     of the new session, the process group leader of the new pro-
     cess  group,  and has no controlling tty.  The process group
     ID and session ID of the calling process are set to the  PID
     of  the  calling  process.   The calling process will be the
     only process in this new process group and in this new  ses-
     sion.


RETURN VALUE

     The session ID of the calling process.


ERRORS

     On error, -1 will be returned.  The  only  error  which  can
     happen is EPERM. It is returned when the process group ID of
     any process equals the PID of the calling process. Thus,  in
     particular, setsid fails if the calling process is already a
     process group leader.


NOTES

     A process group leader is a process with  process  group  ID
     equal  to  its  PID.  In  order  to be sure that setsid will
     succeed, fork and exit, and have the child do setsid().


CONFORMING TO

     POSIX, SVr4.


SEE ALSO

     setpgid(2), setpgrp(2)