Path: utzoo!attcan!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!evax!utacfd!merch!sneaky!gordon
From: gordon@sneaky.UUCP (Gordon Burditt)
Newsgroups: comp.unix.internals
Subject: Re: How do you find the symbolic links to files.
Message-ID: <44075@sneaky.UUCP>
Date: 19 Dec 90 07:55:22 GMT
References: <6647:Dec619:11:3690@kramden.acf.nyu.edu> <1990Dec7.192441.24778@dg-rtp.dg.com> <2707:Dec1001:26:4290@kramden.acf.nyu.edu>
Organization: Gordon Burditt
Lines: 23

>Sorry. What I meant was that the archiver can just squish the first N
>zero-filled blocks it finds into holes. Then it writes zeros into the
>remaining zero-filled blocks.

There seems to be a prevailing theory that this method is portable.
You take the value of st_blocks, the st_size of the file, any other
portable fields of the stat structure you want, and the somehow-obtained 
block size (I'll grant that there may be a portable way of figuring this
out, if we limit this to systems that have st_blocks), and <handwave> 
<mumble> <black magic> obtain this mysterious value of N by way of
another mysterious value of "number of blocks of holes we need to leave".  

Is there a portable way of computing this, without going to the raw disk
and without write permission on the original file?

You may NOT assume that the number of blocks in an indirect block is known,
how many block numbers an indirect block holds, how many blocks are required
to record the presence of holes ("excavation licenses"), nor that said 
numbers of blocks are independent of the order in which the file was filled 
in.

					Gordon L. Burditt
					sneaky.lonestar.org!gordon