From mboxrd@z Thu Jan  1 00:00:00 1970
From: Enache Adrian <enache@rdslink.ro>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] ls, rc question -- proposed change to rc/glob.c
Message-ID: <20040321232928.GA1197@ratsnest.hole>
References: <393a7f63e7c4973e661988f1009f5d7a@vitanuova.com> <Pine.LNX.4.44.0403211446060.22122-100000@maxroach.lanl.gov>
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In-Reply-To: <Pine.LNX.4.44.0403211446060.22122-100000@maxroach.lanl.gov>
Date: Mon, 22 Mar 2004 01:29:28 +0200
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On Sun, Mar 21, 2004 a.d., ron minnich wrote:
> should these yield the same results? If you don't care, then the libc.a 
> approach is fine. If you do want the same results, I think you may be 
> stuck doing the uniqueness tricks in the kernel a la BSD, which to me 
> anyway is unattractive.

I'm afraid the uniqueness tricks are done in library/userland in BSD.
(the McKusick paper referred to in lexnames.html already tells it).
Just try to read a "-o union" mounted directory with open/getdirentries.

The hack is in libc/gen/opendir.c. Quoting from there:
                /*
                 * The strategy here is to read all the directory
                 * entries into a buffer, sort the buffer, and
                 * remove duplicate entries by setting the inode
                 * number to zero.
                 */
Only bloating the kernel with a sort/uniq filter could be worse than that.

Regards,
Adi