From: utzoo!decvax!decwrl!sun!megatest!fortune!hpda!hplabs!hao!seismo!rlgvax!guy
Newsgroups: net.unix-wizards
Title: Re: mutual exclusion between processes
Article-I.D.: rlgvax.173
Posted: Thu Mar 31 11:52:13 1983
Received: Sun Apr  3 03:53:20 1983
References: sri-arpa.745

USG UNIX (and, I believe, 4.2BSD)has a cute trick for this; if you do an "open"
with the O_CREAT and O_EXCL bits on in the second argument (note; you can do
a create and have the resulting descriptor open for writing *and* reading -
it's about time!), if the file already exists an EEXIST error will be returned,
and the file will be untouched - even if you are the super-user.

					Guy Harris
					RLG Corporation
					{seismo,mcnc,we13}!rlgvax!guy