03-shell recording

The various things I demoed in the shell in lecture 3. I first show the commands for managing processes: ps to see what processes you are running, kill to terminate a process, and top to see usage of system resources. Then I show a few of the features of the emacs editor (guide here). Finally, I demo some aspects of programming in the shell: how to declare and reference variables, how to compute mathematical expressions, how to use shell commands as part of other commands, and the for loop syntax.