It is way to expensive to write the whole file. That's why I proposed
to only write the last byte. This will force the OS to really map the
file on the systems less POSIX compliant.
george.
On Mar 28, 2009, at 13:50 , Jeff Squyres wrote:
How about just write()ing a bunch of 0's instead of using ftruncate?
On Mar 27, 2009, at 11:09 PM, Eugene Loh wrote:
Paul H. Hargrove wrote:
> Quoting from a different manpage for ftruncate:
> [T]he POSIX standard allows two behaviours for ftruncate
> when length exceeds the file length [...]: either
returning an
> error, or
> extending the file.
> So, if that is to be trusted, it is not legal by POSIX to
*silently*
> not extend the file.
On a Solaris system, the ftruncate man page says:
truncate, ftruncate - set a file to a specified length
The truncate() function causes the regular file named by
path to have a size 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.
So, the sense is not of "truncating" (shortening) per se, but of
fixing
a new length, whether that length is longer or shorter.
I guess we could try to track down the ftruncate behavior on the
systems
in question, but (IMHO) this doesn't feel like the correct
explanation.
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Jeff Squyres
Cisco Systems
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