setsid(2)                        UNIX System V                        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).

NOTES
      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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