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Date:      Tue, 1 Aug 2006 14:26:28 -0400
From:      Mike Meyer <mwm-keyword-freebsdhackers2.e313df@mired.org>
To:        rick-freebsd@kiwi-computer.com
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: [PATCH] adding two new options to 'cp'
Message-ID:  <17615.40148.872008.53973@bhuda.mired.org>
In-Reply-To: <20060801171150.GB3413@megan.kiwi-computer.com>
References:  <200607271150.k6RBoM9p031745@lurza.secnetix.de> <44C8FB65.9020102@FreeBSD.org> <44CE03D2.2050803@centtech.com> <17614.4005.407223.621637@bhuda.mired.org> <44CE199C.2020500@centtech.com> <17614.8289.134373.387558@bhuda.mired.org> <96b30c400607310847s1d2f845eo212b234d03f51e9a@mail.gmail.com> <17614.10982.499561.139268@bhuda.mired.org> <ealpn1$lan$1@sea.gmane.org> <20060801072611.GA717@turion.vk2pj.dyndns.org> <20060801171150.GB3413@megan.kiwi-computer.com>

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In <20060801171150.GB3413@megan.kiwi-computer.com>, Rick C. Petty <rick-freebsd@kiwi-computer.com> typed:
> On Tue, Aug 01, 2006 at 05:26:11PM +1000, Peter Jeremy wrote:
> > On Mon, 2006-Jul-31 22:42:49 +0200, Ivan Voras wrote:
> > >I agree with this, and while you're in there, can you add -s to copy 
> > >sparse files (via the usual "if the buffer is all nulls, seek beyond eof 
> > >instead of writing" trick)?
> > 
> > Note that it isn's possible to accurately distinguish between a block
> > of NULs and a hole in the file through the filesystem.  The only way
> > to accurately copy a sparse file is with dump/restore.
> 
> Sure it is-- in a number of ways.  The most useful way is to do something
> of the sort:

[code elided]

> Obviously, I didn't add the error checking/handling, but AFAIK this is
> essentially what the -S option to gnu's tar does.

Yes, but gnu tar doesn't do this accurately, so you're not doing what
Peter said you couldn't do. You are doing what Ivan asked, though.

I always think of cp as a tool for making *copies of files*, not for
creating an archive of a directory tree. We've got lots of tools that
do the latter. Do we really need another one?

	<mike
-- 
Mike Meyer <mwm@mired.org>		http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.



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