Daniel's script doesn't run on Ubuntu out of the box, but a one line change can fix that.  If you look at the top of the script, you'll see that he uses /bin/sh as the environment:

#!/bin/sh

However, for some reason or other, Ubuntu, and various off shoots of it, don't seem to have the 'let' command in /bin/sh (note though that RHEL based systems do, at least the CADE lab itself does, as well as OS X).

Anyway, this can be easily fixed by changing that first line to say:

#!/bin/bash

Hope this information helps any other students who run Ubuntu, or one of it's variants.

~Leif Andersen