mutual exclusion write access

[Falko Bause]

I want to allow only mutually exclusive write-accesses to a certain file.
I've searched through the manual pages and have only found commands
like lockf. But these commands only allow to establish a mutual
exlusive access for sub-processes of some process.

Let's explain, what I want, through an example:

There is a file (e.g.) named   text. I want that the following commands
getting only exclusive write access:
	du > text
	ls -R > text
	myprog > text        etc.


I think that this a basic problem and therefore UNIX should have some 
buildins. E.g. VAX/VMS and Apollo/Aegis support setting some file
attributes and mutual exclusion is performed by the operating system.
But chmod, I think, doesn't has this possibility.

Is there an easy way to perform mutual exclusion?

Thanks in advance

	Falko