sparsify - utility to punch out blocks of 0s in a file

Eric Sandeen sandeen at
Sun Feb 5 11:21:26 CST 2012

On 2/5/12 11:19 AM, Ron Yorston wrote:
> OK, I tried it out for my use case of flinging VM filesystem images around
> on ext4 and it seems to do the job.  I don't have any 64-bit systems
> here at home so I used my feeble 32-bit netbook.  Since sizeof(off_t) !=
> sizeof(long long) the debug output was all wrong:
>    punching at 8989607068975104 len -4635819229210214401

whoops, I'll fix that thanks.

This is the problem when I start something as a hack and then expose it
to the light of day.  ;)


> but the image file and the host filesystem both survived the ordeal.
> Ron

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