On Wed, 11 Feb 1998, Darren Reed wrote:
> if [ ! -e foo ] ; then
> 	touch foo
> fi
> 
> - race condition between test and touch running.

Does this work?

	touch foo.new.$$  # XXX: we hope that this is a unique name
	ln foo.new.$$ foo # atomic operation, fails if foo exists
	rm -f foo.new.$$  # delete temp file unconditionally

--apb (Alan Barrett)