Andrew Lentvorski wrote:
> Gus Wirth wrote:
>> Andrew Lentvorski wrote:
>>> Is there a quick way to remove the last 10 bytes from a big honking
>>> file?
>>
>> I asked this same question a while ago and the answer is no. Just
>> about every solution you get involves making a copy somewhat along the
>> lines of using dd to copy everything but the last few bytes. My
>> application was to trim the last block off a ISO image obtained by
>> doing a dd of a CDROM/DVD.
>>
>> The problem arises because of the virtualization of file systems. It
>> takes direct intimate relations with the underlying file system to be
>> able to manipulate the file size indicators and to move the last
>> pointer /extent/branch/whatever-they-use-for-the-filesystem.
>>
>> I've seen a reference to a utility for use on ext2 file systems, but I
>> can't remember what I did with it. I think fat and fat32 file systems
>> have simple utilities for trimming files left over from the DOS days
>> that may be "good enough" depending on what you are doing.
>
> FWIW, this works okay:
>
> andrewl$ ls -al junk.txt
> -rw-r--r-- 1 andrewl andrewl 1073741824 Aug 28 01:45 junk.txt
> andrewl$ ipython
> Python 2.5.1 (r251:54863, Aug 19 2007, 00:42:28)
> Type "copyright", "credits" or "license" for more information.
>
> IPython 0.8.1 -- An enhanced Interactive Python.
> ? -> Introduction to IPython's features.
> %magic -> Information about IPython's 'magic' % functions.
> help -> Python's own help system.
> object? -> Details about 'object'. ?object also works, ?? prints more.
>
> In [1]: ff = open("junk.txt", "wb")
>
> In [2]: ff.truncate(500000000)
>
> In [3]: ff.close()
>
> In [4]:
> Do you really want to exit ([y]/n)? y
> andrewl$ ls -al junk.txt
> -rw-r--r-- 1 andrewl andrewl 500000000 Aug 28 01:46 junk.txt
>
Ah, I wondered if it was in python. Of course!
Thanks.
Regards,
..jim
.. are you watching the lunar eclipse? nice big ring effect right now
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