Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!decwrl!sun!pitstop!sundc!seismo!uunet!mcvax!ukc!warwick!cudcv
From: cudcv@warwick.ac.uk (Rob McMahon)
Newsgroups: comp.mail.elm
Subject: Re: newmail also displays on console (bug)
Message-ID: <117@titania.warwick.ac.uk>
Date: 6 Mar 89 21:29:00 GMT
References: <316@wubios.wustl.edu> <890001@hpausla.HP.COM> <5142@b-tech.ann-arbor.mi.us> <4774@pbhyf.PacBell.COM> <2918@epimass.EPI.COM>
Reply-To: cudcv@warwick.ac.uk (Rob McMahon)
Organization: Computing Services, Warwick University, UK
Lines: 34

In article <2918@epimass.EPI.COM> jbuck@epimass.EPI.COM (Joe Buck) writes:
>In article <4774@pbhyf.PacBell.COM> rob@pbhyf.PacBell.COM (Rob$Bernardo) writes:
>>Newmail already obeys SIGHUP. This particular user's environment is such that
>>the SIGHUP is not being sent to newmail and that's the problem.
>
>This particular user's environment is quite common: under the Bourne shell,
>background processes don't ingnore hangup unless you use the "nohup" command,
>but under the C shell they do by default.

No, this is the wrong problem, Rob Bernado was correct.  When you log out (at
least Berkeley) Unix sends a SIGHUP to the process group of the terminal.  With
the Bourne shell this means all processes run from that shell, because it does
no process group manipulation.  The C-Shell, however, puts each `job' in it's
own process group, so that the shell can manipulate who's allowed to talk to
the terminal.  It does not cause SIGHUPs to be ignored when you background a
job, it's just that the jobs never get a SIGHUP, because they're not in the
process group of the terminal.  Presumably other shells with job control must
do the same.

>One solution is to define AUTO_BACKGROUND and have people run newmail without
>doing ampersands.

Right.

>Another is to explicitly catch SIGHUP instead of keeping the default behavior,
>which, as you say, depends on the environment.

No, the process never gets a SIGHUP.

Rob
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Rob McMahon, Computing Services, Warwick University, Coventry CV4 7AL, England