First I thought of C because it will also teach him how the Linux he runs was made. But… I hate C. I personnally learned programming with OCaml and Pascal. I still love OCaml (pattern matching FTW), but it didn't really teach me anything about Unix…
I'm looking for a language that would be easy to learn, with a beautiful syntax, and that would gently introduce a 13 year old to the amazing world of Unix/Linux.
Any ideas?