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From: guy@sun.uucp (Guy Harris)
Newsgroups: net.sources.games
Subject: Re: problems with galaxy/robots/others on Sys V Rel 2
Message-ID: <2319@sun.uucp>
Date: Tue, 18-Jun-85 04:11:35 EDT
Article-I.D.: sun.2319
Posted: Tue Jun 18 04:11:35 1985
Date-Received: Thu, 20-Jun-85 07:46:55 EDT
References: <739@burl.UUCP> <338@cuae2.UUCP>
Organization: Sun Microsystems, Inc.
Lines: 20

> > The problems mentioned compiling galaxy, robots, and others are
> > due to the use of the flock() utility of BSD, which Sys V does
> > not have.  flock() is a general-purpose advisory lock routine...

> UNIX System V Rel. 2 does support file locking through the fcntl system
> call.

UNIX S5R2V2 (for the VAX, anyway) supports file locking, but S5R2V1 doesn't.
This caused a problem when a "System V compatible" version of one of the
aforementioned games didn't build on a System V system.

Until such time as every UNIX system out there supports file locking, you
might want to consider the "old reliable" link mechanism.  Each file to be
locked has a file associated with it (which can be the file itself).  To
lock the file, make a link to the associated file (which has a well-known
name) with another well-known name.  If the link already exists (i.e., the
file is locked), the link will fail.  "unlink" unlocks the file.  Crude, but
effective, and it works on every UNIX out there.

	Guy Harris