Almquist Shell: Difference between revisions
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Ash has three major variants: |
Ash has three major variants: |
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* [[Debian Almquist Shell]] (Dash), which adds support for |
* [[Debian Almquist Shell]] (Dash), which adds support for <tt>echo -n</tt> and <tt>test -a</tt>/<tt>-o</tt> |
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* [http://svnweb.freebsd.org/base/head/bin/sh/ FreeBSD /bin/sh] |
* [http://svnweb.freebsd.org/base/head/bin/sh/ FreeBSD /bin/sh] |
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* [http://cvsweb.netbsd.org/bsdweb.cgi/src/bin/sh/?only_with_tag=MAIN NetBSD /bin/sh] |
* [http://cvsweb.netbsd.org/bsdweb.cgi/src/bin/sh/?only_with_tag=MAIN NetBSD /bin/sh] |
Revision as of 20:03, 20 September 2022
Almquist Shell is a minimal implementation of an almost-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 local
variables in functions. Almquist Shell is the default shell, /bin/sh
, of some systems. However, it does not have any of the internationalization/localization or multi-byte character encoding support required by the POSIX standard, so it is not a POSIX-compliant shell.
If a script works with Almquist Shell, it will probably also work with bash, pdksh and zsh. Further, it will probably work with ksh93 unless it uses local
, which ksh93 lacks.
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:
- Debian Almquist Shell (Dash), which adds support for echo -n and test -a/-o
- FreeBSD /bin/sh
- NetBSD /bin/sh
All three variants have similar features. Dash can run on GNU/Linux.
Ash is also the shell provided by BusyBox.
See also
- Almquist shell, Wikipedia's article
- Ash (Almquist Shell) Variants, a history of many Ash versions and their features