Creating huge data in very less time.

Dave Angel davea at
Tue Mar 31 21:38:16 CEST 2009

The FAT file system does not support sparse files.  They were added in 
NTFS, in the Windows 2000 timeframe, to my recollection.

Don't try to install NTFS on a floppy.

Grant Edwards wrote:
> On 2009-03-31, Dave Angel <davea at> wrote:
>> I wrote a tiny DOS program called resize that simply did a
>> seek out to a (user specified) point, and wrote zero bytes.
>> One (documented) side effect of DOS was that writing zero
>> bytes would truncate the file at that point.  But it also
>> worked to extend the file to that point without writing any
>> actual data.  The net effect was that it adjusted the FAT 
>> table, and none of the data.  It was used frequently for file
>> recovery, unformatting, etc.  And it was very fast.
>> Unfortunately, although the program still ran under NT (which includes 
>> Win 2000, XP, ...), the security system insists on zeroing all the 
>> intervening sectors, which takes much time, obviously.
> Why would it even _allocate_ intevening sectors?  That's pretty
> brain-dead.
>>> Is there a way to create a file to big withouth actually writing
>>> anything in python (just give me the garbage that is already on the
>>> disk)?
> No.  That would be a monstrous security hole.

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