plumb is a shell with focus on pipes: instead of pipelines, it can build large graphs of processes (nodes) and pipes (edges). Pipes are simple unidirectional streams without side effects. Traffic can be controlled by virtual processes (which are nodes just like real processes, but are implemented in plumb for minimal overhead). Virtual processes can split, merge, regex filter/alter, and shape the streams. Timers and starting/stopping processes or even rewiring the script on the fly are also supported. It is portable (using libporty) and behaves exactly the same way on Linux, Windows, Mac OS X, many BSD variants, and older UNIX systems.
