NB: These days you might prefer inferior-shell for its wider support and richer interface.
Trivial shell is a simple platform independent interface to the underlying Operating System. It forks and builds on the code in Kevin Rosenberg's handy KMRCL tools. More details can be found on its home page at Common-Lisp.net. Presently, the package is quite rudimentary (even for something trivial!) but we all live in hope.