Note: This quesiton is NOT show me which files are in use. The file is not currently in use. The file will be in use at some unknown point in the future. At that point, I want to know what process accessed the file.
I would like to be able to track a file and see which process is touching that file. Is that possible? I know that I can see the list of open processes in activity monitor but I think it's happening to quickly for me to see it. The reason for this is I'm using a framework and I think the system version of the framework is being used instead of the debug version and I'd like to see which process is touching it.
lsof will list open files, but it can be a bit awkward for momentary touches (eg, if the file isn't open when lsof runs, it doesn't show).
I think your best bet would be fernLightning's fseventer.app. It's "nagware", and allows you to watch (graphically) the fsevents API in real-time.