How to process input and output streams in Steel Bank Common Lisp?

“I’m trying to figure out how to use the output stream of one program I start with RUN-PROGRAM so it can be used as the input of another program started with RUN-PROGRAM (i.e., the moral and perhaps literal equivalent of piping). I’ve tried using a number of combinations of the :INPUT, :OUTPUT and :WAIT keyword arguments, but nothing I’ve hit upon has been productive so far. Any tips would be helpful; for example, how would I go about doing something like ls | grep lisp from the shell?…”