editing a binary file

[ocean]

Anton Shterenlikht wrote:
> 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
>