NAME

       setsid - creates a session and sets the process group ID

SYNOPSIS

       #include <unistd.h>

       pid_t setsid(void);

DESCRIPTION

       setsid()  creates a new session if the calling process is not a process group leader.  The
       calling process is the leader of the new session, the process  group  leader  of  the  new
       process  group,  and  has no controlling terminal.  The process group ID and session ID of
       the calling process are set to the PID of the calling process.  The calling  process  will
       be the only process in this new process group and in this new session.

RETURN VALUE

       On success, the (new) session ID of the calling process is returned.  On error, (pid_t) -1
       is returned, and errno is set to indicate the error.

ERRORS

       EPERM  The process group ID of any process equals the PID of the calling  process.   Thus,
              in  particular,  setsid()  fails  if the calling process is already a process group
              leader.

CONFORMING TO

       SVr4, POSIX.1-2001.

NOTES

       A child created via fork(2) inherits its parent's session ID.  The session ID is preserved
       across an execve(2).

       A  process  group leader is a process with process group ID equal to its PID.  In order to
       be sure that setsid() will succeed, fork(2) and _exit(2), and have the child do setsid().

SEE ALSO

       setsid(1), getsid(2), setpgid(2), setpgrp(2), tcgetsid(3), credentials(7)

COLOPHON

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