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From: McGuire_Ed@GRINNELL.MAILNET.UUCP
Newsgroups: mod.computers.vax
Subject: RE: One way to detect aliased files
Message-ID: <8704081631.AA02136@ucbvax.Berkeley.EDU>
Date: Tue, 7-Apr-87 13:46:00 EST
Article-I.D.: ucbvax.8704081631.AA02136
Posted: Tue Apr  7 13:46:00 1987
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> Date: 6 APR 87 17:15-PDT
> From: JWHITNEY%UWARITA.BITNET@wiscvm.wisc.edu
> Subject: One way to detect aliased files
>
> The best way I have found to detect aliases is to do a DIRECTORY/FILE_ID.
> Two entries with the same file id are duplicate-link files.  As for detecting
> which is the original, I am unsure.

The file has a backlink to its parent directory.  When you enter a file in a
second directory, the backlink can still only point to one directory.  The
backlink is not changed by SET FILE/ENTER.

To see the backlink, use DUMP/HEADER.  It will tell you the file id of the
parent directory.  Note that it does not tell you the _name_ of the directory.

So, if you have a file entered in multiple directories whose names you know,
compare the backlink id with the id of the .DIR files to see which one was
the original.

Caveat: When you run ANALYZE/DISK/REPAIR, the utility notices that the file
is not backlinked to the second and succeeding directories.  It `repairs'
this condition by changing the file's backlink to point to a different
directory.  So, the info you get from DUMP/HEADER only tells you about the
original directory if you haven't yet run ANALYZE/DISK/REPAIR.

And everyone runs ANALYZE/DISK/REPAIR regularly, right?  :-)

Ed McGuire
Grinnell College
MCGUIRE@GRIN2.BITNET