From: Steven L Baur <steve@miranova.com>
Date: Mon, 15 Jul 1996 06:30:09 +0800
To: mcarpent@mailhost.tcs.tulane.edu
Subject: Re: Execution of signed scripts received by e-mail
In-Reply-To: <199607141042.FAA01300@Dusk.obscure.net>
Message-ID: <m2pw5yu10s.fsf@deanna.miranova.com>
MIME-Version: 1.0
Content-Type: text/plain


>>>>> "Matt" == Matt Carpenter <mcarpent@Dusk.obscure.net> writes:
>>>>> "Hal" == Hal <hfinney@shell.portal.com> writes:

Hal> That sounds very impressive!  The one problem I've run into with
Hal> mail filtering software is that each message asynchronously
Hal> spawns a separate filter process.  This can cause some conflicts
Hal> with accessing disk files.

Matt> If I am reading the procmail docs correctly, then the following
Matt> recipe should create a lockfile called 'emscrypt.lock' which
Matt> will prevent more than one instance of the script from being run
Matt> at a time

Matt> :0:emscrypt
Matt> ^ Subject.*SQUEAMISH OSSIFRAGE
Matt> |/PATH/emscrypt

That is half correct.  It will only create emscrypt.lock if you have
configured procmail for that kind of locking, otherwise it will use
lockf or flock to make the lock.

As Hal pointed out, you will still have one process per message, but
they will be processed one at a time.

Matt> I agree it would be better if emscrypt used its own locks on the
Matt> timestamp files.  However, it is my understanding (someone
Matt> please correct me if I am wrong) that there is no simple way to
Matt> provide file locking in Perl that is portable across the various
Matt> flavours of Unix (see the descriptions of the fcntl and flock
Matt> functions on p. 144-145 of the Camel book).

Another possibility is to call lockfile (a program included with
procmail which performs compatible locking).

You're better off using procmail's locking as it does what you're
looking for, and many people have beat on the code over the years.

-- 
steve@miranova.com baur
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