# -*- coding: utf-8 -*-
-
# Public Domain
#
# Copyright 2007, 2009 Sander Marechal <s.marechal@jejik.com>
for details (ISBN 0201563177)
Short explanation:
- Unix processes belong to "process group" which in turn lies within a "session".
- A session can have a controlling tty.
+ Unix processes belong to "process group" which in turn lies within a
+ "session". A session can have a controlling tty.
Forking twice allows to detach the session from a possible tty.
The process lives then within the init process.
"""