sunos man page for setsid

setsid(2)							   System Calls 							 setsid(2)

NAME
       setsid - create session and set process group ID

SYNOPSIS
       #include <sys/types.h>
       #include <unistd.h>

       pid_t setsid(void);

DESCRIPTION
       The  setsid() function creates a new session, if the calling process is not a process group leader. Upon return the calling process will be
       the session leader of this new session, will be the process group leader of a new process group, and will have no controlling terminal. The
       process	group	ID of the calling process will be set equal to the process ID of the calling process. The calling process will be the only
       process in the new process group and the only process in the new session.

RETURN VALUES
       Upon successful completion, setsid() returns the value of the process group  ID of the calling process. Otherwise it returns (pid_t)-1  and
       sets errno to indicate the error.

ERRORS
       The setsid() function will fail if:

       EPERM	       The calling process is already a process group leader, or the process group  ID of a process other than the calling process
		       matches the process  ID of the calling process.

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Async-Signal-Safe 	   |
       +-----------------------------+-----------------------------+

SEE ALSO
       getsid(2), setpgid(2), setpgrp(2), attributes(5), standards(5)

WARNINGS
       A call to setsid() by a process that is a process group leader will fail. A process can become a process group leader  by  being  the  last
       member of a pipeline started by a job control shell. Thus, a process that expects to be part of a pipeline, and that calls setsid(), should
       always first fork; the parent should exit and the child should call setsid(). This will ensure that the calling process will work  reliably
       when started by both job control shells and non-job control shells.

SunOS 5.10							    21 Aug 2002 							 setsid(2)