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Date:      Fri, 19 Nov 2010 19:16:53 +0100
From:      Hans Petter Selasky <hselasky@c2i.net>
To:        Matthias Apitz <guru@unixarea.de>
Cc:        freebsd-usb@freebsd.org
Subject:   Re: copying /dev/da0 with dd(1) to file: output differs
Message-ID:  <201011191916.53655.hselasky@c2i.net>
In-Reply-To: <20101119173519.GA3933@current.Sisis.de>
References:  <20101119143337.GA3023@current.Sisis.de> <201011191821.09308.hselasky@c2i.net> <20101119173519.GA3933@current.Sisis.de>

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On Friday 19 November 2010 18:35:19 Matthias Apitz wrote:
> El d=EDa Friday, November 19, 2010 a las 06:21:09PM +0100, Hans Petter Se=
lasky=20
escribi=F3:
> > > > Can you dump the data into hex using hexdump -C and show us the
> > > > difference.
> > >=20
> > > Note: the output of the dd(1) is around 3.8 GByte. I compared the 1st
> > > 2.000.000 lines of the hexdump: no diff; any better tool to show the
> > > 1st block which differs?
> > >=20
> > > > Usually you would use bs=3D65536 (Does that change anything)?
> > >=20
> > > Same result: they differ :-(
> > >=20
> > > 	matthias
> >=20
> > bsdiff ?
>=20
> This will not work with such big files (requires 8x memory of the file):
>=20
> I was thinking in a tool just reading each file block by block,
> comparing the blocks and noting the 1st diff with block offset number.
> (some 10 lines of C code :-))
>=20
> 	matthias

Maybe you need to write a small C-program to do that.

You can use bcmp() to compare two buffers.

=2D-HPS



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