Re: Script to set up sparse device for testing

On Thu, Jul 06, 2006 at 05:36:56AM -0600, Matthew Wilcox wrote:
> On Thu, Jul 06, 2006 at 12:05:41PM +0200, Erik Mouw wrote:
> > (IIRC truncate() isn't required to work this way according to
> > POSIX/SUSv3, but it works under Linux).
> 
> The truncate() function shall cause the regular file named by path to
> have a size which shall be equal to length bytes.
> 
> If the file previously was larger than length, the extra data is
> discarded. If the file was previously shorter than length, its size is
> increased, and the extended area appears as if it were zero-filled.
> 
> http://www.opengroup.org/onlinepubs/000095399/functions/truncate.html

Ah, the gory details :)

So truncate shall increase the file and zero fill it, but it doesn't
say it should be a sparse file. I suppose that's left to the
implementation.


Erik

-- 
+-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 --
| Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands

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