Re: Stealing a Great Idea from the 6600

On 7/30/2024 6:51 PM, Lawrence D'Oliveiro wrote:

On Mon, 29 Jul 2024 22:40:39 -0500, BGB wrote:
 

If a file has not been modified, and was already confirmed good, you
don't really need to verify it again...

 How do you tell whether it’s been modified or not, without actually
examining its entire contents?

If one is already intercepting every filesystem call, it is possible to keep track of whether a given file was opened for writing, deleted, written to, ...
If a file has not been opened for writing or written to or similar, since the last time it was looked at, it is possible to safely infer that its contents are still the same (assuming a conventional filesystem, like FAT or NTFS or similar).
Alternatively, one could check modification times (like what "make" or similar does), but this is less provable (if there exists any way to modify a file without updating its modification time).