Date: Fri, 18 Dec 2009 09:33:49 -0700 (MST) From: Warren Block <wblock@wonkity.com> To: perryh@pluto.rain.com Cc: glarkin@freebsd.org, mexas@bristol.ac.uk, freebsd-questions@freebsd.org Subject: Re: editing a binary file Message-ID: <alpine.BSF.2.00.0912180904180.11293@lightning.wonkity.com>
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perryh@pluto.rain.com wrote: > Greg Larkin <glarkin@freebsd.org> wrote: > > ... > > > truncate -4 myfile should get rid of the last four bytes. Maybe > > > there's a similar efficient way to truncate the start of a file. > > > > This should do it: > > > > dd if=oldfile of=newfile bs=1 skip=4 > > Or, perhaps marginally more efficient: > > dd if=oldfile of=newfile bs=4 skip=1 It would be nice to avoid the file copy, but maybe there's no way to do that. The small buffer size for dd will probably make copies of multi-gig files slow. This might be faster: tail -c +5 myfile > outfile truncate -4 outfile (Has anyone mentioned that you can edit binary files interactively with vi yet? No? Well, it's horrific and surely has interesting failure modes. And there are probably disadvantages also.) -Warren Block * Rapid City, South Dakota USA
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