setsid(2)                                                         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 process, 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 calling 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 process 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.












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