editing a binary file

[Anton Shterenlikht]

On Fri, Dec 18, 2009 at 09:33:49AM -0700, Warren Block wrote:
> perryh at pluto.rain.com wrote:
> > Greg Larkin <glarkin at 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.)

Vim, yes. I tried, but failed. At the moment dd/truncate combination
seems the most appealing. But I'll look at C/perl/python proposed
solutions as well.

many thanks

-- 
Anton Shterenlikht
Room 2.6, Queen's Building
Mech Eng Dept
Bristol University
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