[Samba] Cases where Samba modifies a file without changing the timestamp?

Logan Shaw lshaw at emitinc.com
Mon Sep 18 23:13:25 GMT 2006

On Tue, 19 Sep 2006, Marc SCHAEFER wrote:
> apart from the mmap(2)ed DBM files that Samba uses, are they any cases
> where Samba will *modify* data files without setting the mtime ?
> I have issues with rsync not seeing changes to Samba exported files
> (md5sum don't match). The mtime is however in the very distant past (say
> 2004), but the content seems to have changed.

Let me guess:  these files' names end in the string ".XLS", right?

>From what I've heard, apparently MS, in their infinite wisdom,
decided it would be neat if Excel wrote things into files and
then set their modification time back to what it was before
modifying the files.  To me, the intent behind "modification
time" seems fairly obvious, but apparently some bright person
at MS has a different interpretation[1].

I'm not sure if MS has any documentation about this phenomenon,
but the Unison folks do mention it in a changelog[2]:

           + Excel files are now handled specially, so that the fastcheck
             optimization is skipped even if the fastcheck flag is set.
             (Excel does some naughty things with modtimes, making this
             optimization unreliable and leading to failures during change

   - Logan

[1] My guess is that Excel writes lock information into
     the document's file, and the MS person decided that
     "modification time" should be interpreted to apply to the
     conceptual document rather than the file, but that's just
     a guess.  Or maybe they were somehow forced into it because
     of http://support.microsoft.com/kb/324491/ .

[2] at https://svn.cis.upenn.edu/svnroot/unison/trunk/src/NEWS .

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