mpsh is an experimental command interpreter for Unix systems written by Dave Fischer at the Center for Computational Aesthetics and distributed under the 3-clause BSD license.

"mpsh" stands for "multi-processor shell", because one of its core features is the ability to split certain jobs into multiple processes.

The major interesting features are:

Job Handlers
Multiprocess Jobs
Environment Variable Command Aliases
Set Theory Operators

mpsh command history and job control features provide access to much more than just command repetition and process ID. See the command history section and jobs section for details.