Path: utzoo!attcan!uunet!mcsun!ukc!stc!root44!gwc
From: gwc@root.co.uk (Geoff Clare)
Newsgroups: comp.unix.questions
Subject: Re: Killing the correct process
Summary: which signal to use?
Message-ID: <1813@root44.co.uk>
Date: 1 Mar 90 15:22:49 GMT
References: <22332@adm.BRL.MIL> <5312@star.cs.vu.nl> <1212@root44.co.uk> <5352@star.cs.vu.nl> <1221@root44.co.uk> <5448@star.cs.vu.nl> <1381@root44.co.uk> <5669@star.cs.vu.nl>
Reply-To: gwc@root.co.uk (Geoff Clare)
Organization: UniSoft Ltd, London, England
Lines: 37

In article <5669@star.cs.vu.nl> maart@cs.vu.nl (Maarten Litmaath) writes:
>
>You're right again!  I've posted another script to alt.sources, which does
>things your way (at last! :-), but having a few extras too.

Glad to hear you've seen the light (at last :-).

Your new script is the same as mine with one worthwhile addition and a
few rather less useful (IMHO) ones.  Thanks for saving me the effort of
implementing my suggested method for tidying up the leftover sleep.

>)>Another plus of timeout 5.0: the signal is now a parameter too.
>)
>)Another unnecessary frill.  SIGTERM is the right signal to use - that's
>)why it's the default for the "kill" command.
>
>Again I don't agree; first there's the generality, then there's the fact
>that SIGHUP is used to signal exceptions too, and lastly both SIGALRM and
>SIGXCPU seem normal to send on a *timeout*.

Sorry, all three signals you mention are not right for this purpose.

SIGHUP:  you might want to do a "nohup timeout somecommand ... &"

SIGALRM: is not for "timing out" a process, it's for use by a process, e.g.
	 for timing out a system call or for sleeping.  If the process is
	 using SIGALRM, all your "time out" will do is wake it up early.

SIGXCPU: is for limiting resource usage, and in any case is non-standard.

The phrase "time out" when applied to a process really means "terminate
before normal completion".  When you want to *TERM*inate a process you use
SIG*TERM*.  Need I say more?
-- 
Geoff Clare, UniSoft Limited, Saunderson House, Hayne Street, London EC1A 9HH
gwc@root.co.uk  (Dumb mailers: ...!uunet!root.co.uk!gwc)  Tel: +44-1-315-6600
                                         (from 6th May 1990): +44-71-315-6600