setsid

SYNOPSIS
       #include <unistd.h>

       pid_t setsid(void);


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

RETURN VALUE
       Upon successful completion, setsid() shall return the value of the  new
       process  group  ID  of the calling process.  Otherwise, it shall return
       (pid_t)-1 and set errno to indicate the error.

ERRORS
       The setsid() function shall 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.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       The setsid() function is similar to the setpgrp() function of System V.
       System V, without job control, groups processes into process groups and
       creates new process groups via setpgrp(); only one process group may be
       part of a login session.

       Job  control allows multiple process groups within a login session.  In
       order to limit job control actions so that they can  only  affect  pro-
       cesses  in  the same login session, this volume of IEEE Std 1003.1-2001
       adds the concept of a session that is created via  setsid().  The  set-
       sid()  function also creates the initial process group contained in the
       session.  Additional process groups can be created  via  the  setpgid()
       function.   A System V process group would correspond to a POSIX System
       Interfaces session containing a single POSIX process group.  Note  that
       this  function requires that the calling process not be a process group
       leader. The usual way to ensure this is true is to create a new process
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard
       is  the  referee document. The original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                  2003                            SETSID(P)