From: Brian Candler <B.Candler@...>
Date: 2003-07-26T00:51:34+09:00
Subject: Re: Confused about locking a file via file.flock(File::LOCK_EX)

On Sat, Jul 26, 2003 at 12:40:51AM +0900, Travis Whitton wrote:
> Flock only works within the same process.

Locking works between processes, but in general locks are "advisory". That
means that process A and process B must both agree to use the locking
protocol. If process A locks a file, that doesn't actually prevent process B
going ahead and writing to the file, if it doesn't bother to get a lock
first.

It gets confusing when there are about 3 different locking mechanisms
(flock, lockf, and some ioctl-locking) but I don't have my Stevens book with
me so I can't give you the gory details :-)

Cheers,

Brian.