setsid(2)                 SYSTEM CALLS                  setsid(2)



NAME
     setsid - set session ID

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

     pidt setsid(void);

DESCRIPTION
     If the calling  process  is  not  already  a  process  group
     leader,  setsid  sets the process group ID and session ID of
     the calling process to the process ID of  the  calling  pro-
     cess, and releases the process's controlling terminal.

     setsid will fail and return an error  if  the  following  is
     true:

     EPERM          The calling  process  is  already  a  process
                    group  leader,  or  there are processes other
                    than the calling process whose process  group
                    ID  is equal to the process ID of the calling
                    process.

SEE ALSO
     intro(2), exec(2), exit(2), fork(2), getpid(2),  getpgid(2),
     getsid(2), setpgid(2), setpgrp, signal(2), sigsend(2).

WARNING
     If the calling process is the  last  member  of  a  pipeline
     started  by a job control shell, the shell may make the cal-
     ling process a process group leader.  The other processes of
     the  pipeline  become members of that process group. In this
     case, the call to setsid will fail.  For this reason, a pro-
     cess  that calls setsid and expects to be part of a pipeline
     should always first fork; the parent  should  exit  and  the
     child  should call setsid, thereby insuring that the process
     will work reliably when started by both job  control  shells
     and non-job control shells.

DIAGNOSTICS
     Upon  successful  completion,  setsid  returns  the  calling
     process's  session  ID. Otherwise, a value of -1 is returned
     and errno is set to indicate the error.











                                                                1