The Almquist shell (ash) is Kenneth Almquist's clone of the Bourne shell. It is a fast, small, POSIX-compatible Unix shell. Ash is useful for running shell scripts, but it does not feature job control or other features that other interactive shells such as bash and ksh offer. The Bourne shell, or sh, was the default Unix shell of Unix Version 7, and replaced the Thompson shell, whose executable file had the same name, sh. ... POSIX is the collective name of a family of related standards specified by the IEEE to define the application program interface for software designed to run on variants of the Unix OS. They are formally designated as IEEE 1003 and the international standard name is ISO/IEC 9945. ... A Unix shell, also called the command line, provides the traditional user interface for the Unix operating system. ... A shell script is a script written for the shell, or command interpreter, of an operating system. ... This article is about the UNIX shell named Bash. ... The Korn shell (ksh) is a Unix shell which was developed by David Korn (AT&T Bell Laboratories) in the mid 1980s. ...

The following is extracted from the Slackware package information: Slackware logo Slackware is a Linux distribution created by Patrick Volkerding of Slackware Linux, Inc. ...

ash (Kenneth Almquist's ash shell)

A lightweight (92K) Bourne compatible shell. Great for machines with low memory, but does not provide all the extras of shells like bash, tcsh, and zsh. Runs most shell scripts compatible with the Bourne shell. Note that under Linux, most scripts seem to use at least some bash-specific syntax. The Slackware setup scripts are a notable exception, since ash is the shell used on the install disks. NetBSD uses ash as its /bin/sh.