Where you were not looking was the POSIX module. That is where setsid() is defined.

EDIT
I went and read it closely. Actually it isn't defined there. It just tells you to see your man page.

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 tty. The pro­ cess group ID and session ID of the calling process are set to the PID of the calling process. The calling pro­ cess will be the only process in this new process group and in this new session.
The usage in the code is absolutely identical to what my man page (Debian) has to say in its notes about this function.

BTW I have been amazed lately at how good Google is for picking up information on random technical things. For instance here is a search on setsid.

In reply to RE: Re: I got zombies by tilly
in thread I got zombies by reptile

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