Monitor changes to a file

[Kurt Granroth]

I need to be able to monitor a file to see when it changes and, more 
importantly, what process is making that change.  Specifically, I run 
the SpiderOak utility every night but *something* (maybe itself) is 
corrupting or rewriting a critical file just before it runs.  I need to 
know what it is that is doing that change.

Tripwire will monitor the file and tell me that it changed... but I 
already know that.  I didn't see any obvious way to get it to tell me 
who changed it.

radmind looks like it might be able to do that... but that's a 
sledgehammer approach that I'd rather avoid.

Maybe incron (cron version of inotify) could trigger a script that runs 
'stat' on the file.  Still wouldn't give me the "who", though.

What am I missing?