Re: fileutils `snapshot' extension

[Russell Senior]

>>>>> "Bob" == Bob Proulx <address@hidden> writes:

Russell> I have run into some issues about what to do in certain
Russell> cases:

Russell> a) what should be the test for "sameness"?  It would be nice
Russell> to rely on stat() information, like: mode, owner, group,
Russell> size, mtime.  What is a reasonably robust set of things to
Russell> check?  I am planning to provide a --pedantic option that
Russell> will also compare data before assuming "sameness", but for
Russell> performance reasons I'd rather that not be the default mode.
Russell> Advice?

Bob> I believe comparing only st_dev and st_ino is sufficient to tell
Bob> if two files are the same.  

Thanks for the reply!

I think I was insufficiently complete in my description of the
problem.

In the usual case (at least as I intend to use this), the two files
being compared will be on different filesystems, so just looking at
st_dev and st_ino won't work.  Part of the idea here is to make *one*
(and hopefully only one) independent copy of data to guard against
hardware failure or mutation of the linked data.  So, what I am
looking for is a predicate that will tell me if two independent copies
of a file are otherwise indistinguishable (as in: `cp -p foo bar').

This desire for an independent copy has some implications for the
symlink problem also.


-- 
Russell Senior         ``The two chiefs turned to each other.        
address@hidden      Bellison uncorked a flood of horrible       
                         profanity, which, translated meant, `This is
                         extremely unusual.' ''