or check out the source to dump- it also efficiently reads around holes 
in files. 
isildur


On Fri, 24 Jan 2003, der Mouse wrote:

> > Is there anything in the kernel that could be used to speed up the
> > dumping of very large, very sparce files?
> 
> > For instance I would like to be able to verify the non-zero parts of
> > the following file:
> 
> > $ ls -ls z
> > 192 -rwxr-xr-x  1 dsl  wheel  14797279232 Jan 24 22:31 z
> 
> > without actually transferring 14Gb of data from kernel to user.
> > (and maybe without filling all of physical memory with 0 bytes).
> 
> Well, it's only a little like what I assume you're looking for, but if
> the file is on an FFS filesystem, I have code that knows how to read
> the disk directly and detect holes in the file that way.
> 
> Drop me a line if you're interested in discussing it further.
> 
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