Idiom for shelling out to $EDITOR/$PAGER?

[Steven D'Aprano]

On Fri, 23 Dec 2011 09:44:31 +0000, Steven D'Aprano wrote:

> On Fri, 23 Dec 2011 09:28:52 +0100, Peter Otten wrote:
> 
>>> -proper & efficient detection of file-change, to know whether the user
>>> actually did anything
>> 
>> Just read the whole thing back into memory and compare the string to
>> the original data. The file has to be quite long for the checksum
>> calculation to be worthwhile.
> 
> I don't think so. No matter how long the file is, the checksum is always
> going to do far more work than a simple string comparison. A string
> comparison can short-circuit on the first difference; the checksum must
> always process both files in their entirety.

Wait... the above only holds assuming you keep both the before-editing 
and after-editing versions. If you don't, then Peter is right, there 
comes a point where keeping a checksum saves enough memory for the 
additional effort to be worth while.

Sorry for the noise.


-- 
Steven