Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!mcvax!ukc!kl-cs!jonathan
From: jonathan@cs.keele.ac.uk (Jonathan Knight)
Newsgroups: comp.mail.misc
Subject: Re: Mail locking...
Message-ID: <548@kl-cs.UUCP>
Date: 22 Mar 89 14:54:42 GMT
References: <588@dtscp1.UUCP>
Organization: University of Keele, England
Lines: 29

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.

I would like to see this posted as its a problem I just bumped into.  I
was installing 'mush' which has just appeared in comp.sources.unix and
I noted that it would lock the mail files by using the *.lock method
and by using flock().  I wanted it to work the same way the BSD 'mail'
worked so I read up on the manual pages.  The manual for /bin/mail said
it used the *.lock method but the manual for '/usr/ucb/mail' didn't
mention any method of mailbox locking.  Seeing as /usr/ucb/mail isn't
a setuid program I assume that it doesn't perform the same locking as
/bin/mail as users don't have write access to /usr/spool/mail.  If
this is the case how does /usr/ucb/mail and /bin/mail avoid writing
to the users mailbox at the same time?

This is an Ultrix 1.2 machine.  (BSD 4.2 ish)


-- 
  ______    JANET :jonathan@uk.ac.keele.cs     Jonathan Knight,
    /       BITNET:jonathan%cs.kl.ac.uk@ukacrl Department of Computer Science
   / _   __ other :jonathan@cs.keele.ac.uk     University of Keele, Keele,
(_/ (_) / / UUCP  :...!ukc!kl-cs!jonathan      Staffordshire.  ST5 5BG.  U.K.