23 Feb
2005
23 Feb
'05
7:47 a.m.
Do you think
the cmp command reads the files up to the end, even if
they have unequal length or a difference at the beginning ???
I am not talking about compare, but about md5. You MUST read it all to
calculate it, no choice. I though about
the first or last kB. Unfortunately, it exist files
having the same beginning (think about zip files containing about the
same content: the beginning is likely to contain the list of
contained files, so is likely to be the same. Think about CD iso
images: the first kB is likely to be the same... I have less examples
with last kB, but CD or floppies images are highly likely to share
the same content. So I think taking the kB closest to the middle of
the file is a good idea, and the entire file content if the file is
less than 1kB in length. Let's call the md5sum of this block the
'signature' of the file.
Beginning, middle, end - statistically, they should be equal, no ?