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From: BGB <cr88192@gmail.com>
Newsgroups: comp.arch
Subject: Re: Stealing a Great Idea from the 6600
Date: Tue, 30 Jul 2024 19:52:14 -0500
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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).