``Locking'' Files

[INGRIA@g.bbn.com]

	I would like to be able to lock a data file so that when one
user is editing it, no one else can edit it (although they might be
able to visit it in read-only mode).  Are there built-in facilities
that allow one to do this?  (There doesn't seem to be any documented
way to do this and my searches for likely sounding candidates haven't
turned up anything).  Has anybody out there already written such a
mechanism?

Thanks in advance.

-30-
Bob Ingria
INGRIA@G.BBN.COM
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