I haven't dug into the puzzle very far and it didn't seem to like my experiments, but in bash and zsh `$$` will expand to the shells PID. Edit: Oh, I see what

I haven't dug into the puzzle very far and it didn't seem to like my experiments, but in bash and zsh `$$` will expand to the shells PID. Edit: Oh, I see what you mean now. I think it's just that you're expected to see that there's only a handful of PIDs in /proc and just try them each.