Write to local CSV (or txt) file on iPad -- access via iTunes

I'm trying to figure out how to write to a local CSV (or TXT) text file on the iPad. I've got UIFileSharingEnabled working--iTunes sees the app as available for file sharing. However, via FileStreram, I can't find where to save the file to? I've tried all the options I know of;

* documentsDirectory

* applicationDirectory

* desktopDirectory

* userDirectory

* applicationStorageDirectory

...but the file doesn't show up in iTunes. Anyone have any suggestions? You game developers must have this figured out for 'high-score' and preferences.

Thanks