Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 (Tek) 9/28/84 based on 9/17/84; site daemon.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!vax135!cornell!uw-beaver!tektronix!daemon!richl
From: richl@daemon.UUCP (Rick Lindsley)
Newsgroups: net.unix-wizards
Subject: Re: 4.2 C Shell does *not* kill stopped jobs on logout.
Message-ID: <567@daemon.UUCP>
Date: Sun, 31-Mar-85 14:31:11 EST
Article-I.D.: daemon.567
Posted: Sun Mar 31 14:31:11 1985
Date-Received: Tue, 2-Apr-85 05:48:15 EST
References: <126@mcc-db.UUCP> <12244@watmath.UUCP>
Reply-To: richl@daemon.UUCP (Rick Lindsley)
Distribution: net
Organization: Tektronix, Beaverton OR
Lines: 28
Summary: 

Let's try to disseminate the correct information. The kernel does not
indiscriminately kill orphan processes. The process only receives a SIGKILL
when a) it is a child of init, and b) when it receives a "keyboard generated"
stop signal (SIGTTOU, SIGTTIN, SIGTSTP). It can be made a child of init by
orphaning it, true, but the given example

	% (date&)&

only fails if the user has tostop set to prevent terminal writes. In that
case it will receive a SIGTTOU as an orphan and be killed. Otherwise it
works fine.

Upon logout, all processes in the terminal process group will receive a
SIGCONT and a SIGHUP. If you are using csh, the only process in the
terminal process group will likely be the csh itself, because csh manipulates
process groups. However, if you had ^Z'ed (SIGTSTP) any processes, then
when you log out they become orphans and are thus SIGKILLed. If a process
is running and its output will not cause a SIGTTOU (because it either
produces none or the output has been redirected into a file) then it will
continue running, untouched. If it were stopped with a SIGSTOP (not a
keyboard generated stop), it will remain stopped.

I might add that this is contrary to the information in tty(4), which states
that orphans are allowed to write to a terminal without fear of a SIGTTOU,
but that is a different story for a different time.

Rick Lindsley
...{allegra,decvax,ihnp4}!tektronix!richl