Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!cbmvax!vu-vlsi!dsinc!syd
From: syd@dsinc.UUCP (Syd Weinstein)
Newsgroups: comp.mail.misc
Subject: Re: Mail locking...
Summary: Its best to do both
Message-ID: <98@dsinc.UUCP>
Date: 23 Mar 89 13:12:05 GMT
References: <588@dtscp1.UUCP> <548@kl-cs.UUCP>
Reply-To: syd@dsinc.UUCP (Syd Weinstein)
Organization: Datacomp Systems, Inc., Huntingdon Valley, PA 19006
Lines: 29

In article <548@kl-cs.UUCP> jonathan@cs.keele.ac.uk (Jonathan Knight) writes:
>From article <588@dtscp1.UUCP>, by scott@dtscp1.UUCP (Scott Barman):
>> I am trying to write some software for mail that will interact with our
>> internal network and must co-exist with the mailers on our bsd-based
>> systems (actually, SunOS 3.5 and SunOS 4.0) and with a System V Release
>> 3.2 system.  I need to know how these systems lock the mail file.
>> Does /usr/.../*.lock work on both of these?  I know that our v7-like
>> system uses the execute bit, but I do not have the sources to the other
>> systems.

Ok, here's a quick overview of locking for mail systems:
Systems that don't use flock() on the spool file itself, use a .lock
file.  Where that file resides depends on the system.

It's difficult to tell which systems use flock and which use .lock if
the system has the flock system call, so most mail user agents use
both to be sure.   You never know when someone puts an older style
user agent on an flock machine, so it doesn't hurt to do both.

BSD and Sys V.2 put the lock file in the mail directory.  Xenix puts
it in /tmp and Sys V.3 puts it in the locks directory.

Elm uses both flock and .lock files whenever possible, and .lock
files if flock is not available.
-- 
=====================================================================
Sydney S. Weinstein, CDP, CCP                   Elm Coordinator
Datacomp Systems, Inc.				Voice: (215) 947-9900
{allegra,bpa,vu-vlsi}!dsinc!syd	                FAX:   (215) 938-0235