From: Jeremy Henty <jeremy@...>
Date: 2006-01-25T00:45:53+09:00
Subject: Re: file locking

On 2006-01-22, Mark Volkmann <r.mark.volkmann@gmail.com> wrote:

> I'm trying to understand usage of file.flock(File::LOCK_SH)
> ... What's the point of a lock if it isn't locking anybody else out?

A shared lock locks out anyone who wants an exclusive lock.  Typically
you want an exclusive lock for writing to a file and a shared lock for
reading it.  That's because it's OK for several people to read a file
simultaneously, but if someone wants to write to it then no-one else
should be allowed to read *or* write, otherwise hilarity may ensue.

Cheers, 

Jeremy Henty