Jon -

Don't the files that grep compares have to be on the machine that's doing the comparison? The problem here is to have a list of the content that's on a bunch of CDs when the CDs are NOT accessible to the computer, in order to find which CD needs to be mounted to retrieve a file.

I casually overlooked that the commands on the OS-X sheet you linked have links to additional explanation, but I'm afraid it didn't help me much. Both "l" and "ls" go to the same web page where switches/variants are shown; but I presume one must have the appropriate vocabulary to fully understand the explanations. The example, that ls lists content of "the current folder" may not get content in subfolders, but of course perhaps the language means something a bit different than I'm accustomed to. I suspect it's actually a lot simpler than it looks.

John