> -----Original Message-----
> From: Dave Thomas [mailto:Dave / PragmaticProgrammer.com]

> 
> I don't believe there's a way to do this on most conventional file
> systems without sing some temporary storage, either memory [or] a
> file.

I figured that memory of some kind would be required.
 
> There are other issues with editing in place: if it blows up half way
> through, you're left with a half-changed file.

A 'rollback' option then. :)
 
> So, the conventional way to do this is to copy the original to a new
> file, then when you're done rename the new file to have the same name
> as the original.

Guy's mmap alternative looks interesting.  I would have thought this was
possible via seek and/or sysread & syswrite.  I was also intrigued by
Mark Jason-Dominus's Tie::File module which appears to cache the file
(up to 2 mb or so by default) into memory.  For those interested, you can
find that module at http://search.cpan.org/search?dis=Tie-File.

Regards,

Dan