So one calls setsid to avoid getting signals from the keyboard. But that can't be all; the OP's question doesn't involve sending signals from the keyboard.

Update: http://en.wikipedia.org/wiki/Process_group answers the question.

In reply to Re^5: Keep a "system" process running if script is prematurely exited? by ikegami
in thread Keep a "system" process running if script is prematurely exited? by westrock2000

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