Say I have two drives, with files like so:
|Drive 01||Drive 02|
|File A||File A|
|File C||File B|
|File D||File C|
|File F||File D|
How do I search in the Finder, or Spotlight, or on the Darwin command line, to locate those files on Drive 02 which are not also on Drive 01? Ie, in the above array, I want to detect that Drive 02\File B exists, and is not present on Drive 01. I don't care about Drive 1\File F...I already know where it is.
(Yes, I messed up a backup-and-restore a while back. I caught it before I'd wiped the now-displaced data, but I'm finally getting to the point where I need to retrieve it from the idled backup disk so I can put that back into service.)