Scsh is a Unix shell embedded in Scheme. It provides full access to 
POSIX as well as extensions common to most Unix implementations. Scsh 
also features many abstractions to ease system programming: process 
abstraction, event-based interrupt handling, sophisticated I/O support 
and enables concurrent system programming.

Scsh is built on top of Scheme 48, a portable R5RS-compliant Scheme 
implementation with byte-code compilation, user-level threads, and 
many useful extensions.