SETSID(2) Linux Programmer's Manual SETSID(2)
setsid - creates a session and sets the process group ID
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.
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.
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
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().
setsid(1), getsid(2), setpgid(2), setpgrp(2), tcgetsid(3), credentials(7)
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Linux 2013-02-11 SETSID(2)