How would you test a developer that claims to have *nix shell experience (just to be clear, we don't want to test if someone can develop on *nix, only that they know their way around the command line).

I was thinking about making them solve a problem of getting information out of log files, which would involve some basics like cat, grep, cut, ... combined with piping.

What other basic knowledge would you ask for? Once again, this isn't for interviewing someone who will develop for *nix systems, and also not for *nix system admins, but just for regular developers that sometimes need to do some work on a *nix system.