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Date: Fri, 10 Aug 2007 09:52:53 -0500
From: Erik Osterholm <freebsd-lists-erik@erikosterholm.org>
To: Jerry McAllister <jerrymc@msu.edu>
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Cc: "V.I.Victor" <idmc_vivr@intgdev.com>, freebsd-questions@freebsd.org
Subject: Re: Utility to change a byte in a binary file?
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On Thu, Aug 09, 2007 at 06:02:54PM -0400, Jerry McAllister wrote:
> On Thu, Aug 09, 2007 at 08:25:17PM +0000, V.I.Victor wrote:
> 
> > 
> > It sure seems that this should be simple, but my searches have only 
> > turned up inter-active hex/disk editors.  I'm probably "asking" wrong.
> > 
> > I have a large binary file (>700 meg) and I know that there is a 
> > single wrong byte.  I also know it's exact location in the file.
> > 
> > Is there a command-line utility to write a byte at a specified offset 
> > into a file? 
> 
> You could try 'dd' and manipulate the skip/offset and size arguments.
> 
> ////jerry

If you use vim, you can do this using vim and xxd:

http://www.vim.org/htmldoc/usr_23.html#23.4

Skip down to the section entitled "USING XXD."  Don't forget to
convert it back before you save!

Erik