Path: utzoo!utgpu!water!watmath!clyde!rutgers!mcnc!decvax!decwrl!sun!pitstop!sundc!seismo!uunet!mcvax!ukc!its63b!simon
From: simon@its63b.ed.ac.uk (ECSC68 S Brown CS)
Newsgroups: comp.unix.questions
Subject: Re: setting the control terminal (how?)
Message-ID: <876@its63b.ed.ac.uk>
Date: 11 Jan 88 00:32:38 GMT
References: <435@picuxa.UUCP> <232@sortac.UUCP>
Reply-To: simon@lfcs.ed.ac.uk (Simon Brown)
Organization: LFCS, University of Edinburgh
Lines: 29

In article <232@sortac.UUCP> pls@sortac.UUCP (Pat Sullivan) writes:
>The setpgrp system calls in all versions of System V that I've seen
>contain the same bug (feature??), which is actually rooted in the
>tty drivers.  The tty drivers do not always completely release their
>controlling terminal when they are supposed to; this often prevents
>"setpgrp" from functioning as one would expect.

A setpgrp() will fail to work in a process which has already done a setgprp().
This happens most if a login-shell tries to grab a new terminal; it's doomed
to failure, because a login-shell is exec'd by the getty program which has
already done a setpgrp(). [It might be init that actually does it - I forget].

The really annoying part is that it doesn't *completely* release the control
tty - it might be just about bearable if it left the original tty in place,
but oh no, it has to leave you hanging in limbo instead.

	--Simon.


-- 
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| Simon Brown                                    |
| Laboratory for Foundations of Computer Science |
| Department of Computer Science                 |
| University of Edinburgh, Scotland, UK.         |
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