Plan 9 from User Space Plan 9 from User Space (aka plan9port) is a port of many Plan 9 programs from their native Plan 9 environment to Unix-like operating systems.

Plan 9 offered a fascinating service-oriented extension of the UNIX "Everything is a file" metaphor, treating the keyboard, the mouse, services on the network, and even individual UI elements in windows as pipe-able files. See also http://plan9.bell-labs.com/plan9/index.html .