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From: zwicky@erg.sri.com (Elizabeth Zwicky)
Newsgroups: comp.unix.internals
Subject: Re: How do you find the symbolic links to files.
Message-ID: <1990Dec10.191522.2757@erg.sri.com>
Date: 10 Dec 90 19:15:22 GMT
References: <6647:Dec619:11:3690@kramden.acf.nyu.edu> <1990Dec7.192441.24778@dg-rtp.dg.com> <2469:Dec1001:13:4390@kramden.acf.nyu.edu>
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In article <2469:Dec1001:13:4390@kramden.acf.nyu.edu> brnstnd@kramden.acf.nyu.edu (Dan Bernstein) writes:
>Elizabeth said that ``you have to get pretty intimate with the disk'' to
>tell that a file has holes, or something like that. She concluded that
>an archiver can with good conscience restore files with as many holes as
>possible, hence saving as much space as possible.

No, actually, Elizabeth didn't say either of those things. And doesn't
believe the latter at all and requested counter examples.

What I did say is that you cannot tell the difference between a hole
and an equivalent number of nulls without reading raw blocks.
st_blocks at best tells you how many holes there are; it doesn't tell
you *where*. Just as programs may, conceivably, care what st_blocks is
(care to name one that does?), they may also care where the holes are
(I have no examples of this one either, but it's equally imaginable).

I conclude from this that good archivers are not portable. One can
arguably conclude that if you want a portable program, you can in good
conscience restore files with as many holes as possible, since you
can't get it right.

	Elizabeth Zwicky