Sender:	nate AT cartsys DOT com
Message-ID:	<370B9C88.1E9C0005@cartsys.com>
Date:	Wed, 07 Apr 1999 10:57:28 -0700
From:	Nate Eldredge <nate AT cartsys DOT com>
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To:	djgpp AT delorie DOT com
Subject:	Re: file locking
References:	<Pine DOT SUN DOT 3 DOT 91 DOT 990406092755 DOT 6187I-100000 AT is> <ugX21aKg#GA DOT 184 AT rpc1284 DOT daytonoh DOT ncr DOT com>
Reply-To:	djgpp AT delorie DOT com

Tanes Sriviroolchai wrote:
> 
> Eli Zaretskii wrote in message ...
> >
> >
> >> second of all, if you lock a file and another instance tries to write to
> >> it, what happens? how can you see if a file or region is locked?
> >
> >On DOS/Windows or on Unix?
> >
> >On Unix, the other process which tries to write blocks until the file
> >is unlocked.  On DOS/Windows I think the write call fails, but you'll
> >need to try to make sure.
> 
> It should be "On Unix, the other process which tried to write without test
> lock before will be successful. However, if that process test lock
> (with blocked) before write it will be blocked until that file is unlocked.
> Or it will be failed if that process test lock without block."

Confusion between cooperative (`flock') and mandatory (`fcntl',
sometimes) locking.  Cooperative locking means that the process *should*
acquire the lock before writing, but isn't stopped if it doesn't. 
Mandatory means that attempts to access a locked area are blocked; not
all systems implement this.
-- 

Nate Eldredge
nate AT cartsys DOT com

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