Almquist Shell is a minimal implementation of a POSIX shell, and also a replacement for Bourne Shell. Almquist Shell has more features than Bourne Shell, but fewer features than most other shells. (No arrays!) Almquist Shell only implements POSIX features, plus a few BSD traditions, like its
local command. Almquist Shell is the default shell,
/bin/sh, of some systems.
Almquist Shell filled the need for a free shell to replace Bourne Shell. Kenneth Almquist posted the first version of Ash to Usenet group comp.sources.unix at 30 May 1989. It was a clone of SVR3 Bourne Shell. BSD used Ash for
/bin/sh, added features from POSIX, and put a Berkeley copyright on this shell.
 Almquist variants
Ash has three major variants:
All three variants have similar features. Dash can run on GNU/Linux.