Path: utzoo!mnetor!uunet!husc6!bloom-beacon!tut.cis.ohio-state.edu!mailrus!ames!pasteur!ucbvax!CPSWH.CPS.MSU.EDU!rang%cps45x
From: rang%cps45x@CPSWH.CPS.MSU.EDU (Anton Rang)
Newsgroups: comp.os.vms
Subject: TPU question (really reading directories directly)
Message-ID: <8804061157.AA19573@cps45x>
Date: 6 Apr 88 11:57:10 GMT
References: <880402024902.1e3b@CitHex.Caltech.Edu>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
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  Directories *are* very version-dependent.  When a new version of VMS
comes out, it will always be able to read directories produced by an
earlier version, for compatibility.  This doesn't mean that its
directories will be in the same format (compare VMS 3.x with VMS 4.x,
for example--the filename length changed, for one thing).
  In any case (whether you can find a workable definition of the
directory format or not), it is not a good idea to bypass RMS for
directory management.  RMS attempts to maintain directories in a
consistent state across concurrent access, and its routines will
correctly handle changing directories.  It can also handle directories
across the network--the other machine can change the directory at any
time, and RMS won't get confused.  The low-level file locking routines
which do this are user-accessible, but RMS gets very confused if you
use them--it doesn't distinguish between its own locks and yours, and
all kinds of bugchecks start occurring.  In the worst case, at least.
  Moral: If you want to read a directory file directly, make sure that
nobody else is using it--and don't expect it to work right all the
time.

						Anton Rang