|Original author(s)||David Korn|
|Stable release||ksh93u / February 8, 2011|
|License||Eclipse Public License (AT&T KornShell)
Mostly public domain with some GPL (pdksh)
three-clause BSD license and ISC License (mksh)
KornShell (ksh) is a Unix shell which was developed by David Korn at Bell Labs in the early 1980s and announced at USENIX on July 14, 1983. Other early contributors were Bell Labs developers Mike Veach and Pat Sullivan, who wrote the Emacs- and vi-style line editing modes′ code, respectively. KornShell is backward-compatible with the Bourne shell and includes many features of the C shell, inspired by the requests of Bell Labs users.
KornShell complies with POSIX.2, Shell and Utilities, Command Interpreter (IEEE Std 1003.2-1992.)
The Korn shell pioneered the practice of consultative user interface design, with input from Unix shell users, and from mathematical and cognitive psychologists. The user interface, which included a choice of editing styles (the choices included styles based on vi and on two variants of Emacs) was incorporated into, or copied by, most subsequent Unix shells.
Major differences between KornShell and the traditional Bourne shell include:
- Job control, command aliasing, and command history designed after the corresponding C shell features;
- Three WYSIWYG-style line editing modes designed to make an interactive shell session behave like vi, Emacs, or XEmacs;
- Associative arrays and built-in floating point arithmetic operations (only available in the ksh93 version of KornShell);
- Dynamic extensibility of built-in commands (as of ksh93).
Until 2000, KornShell remained AT&T′s proprietary software. Since then it has been open source software, originally under a license particular to AT&T but, since the 93q release in early 2005, it has been licensed under the Common Public License. KornShell is available as part of the AT&T Software Technology (AST) Open Source Software Collection. As KornShell was initially only available through a proprietary license from AT&T, a number of free and open source alternatives were created. These include pdksh, mksh, GNU bash, and zsh.
The functionality of the original KornShell, ksh88, was used as a basis for the standard POSIX.2, Shell and Utilities, Command Interpreter (IEEE Std 1003.2-1992.)
Some vendors still ship their own version of the older ksh88, sometimes with extensions. ksh93 is still maintained by its author. Releases of ksh93 are versioned by appending a letter to the name; the current version is ksh93u, following ksh93t+ (which followed ksh93t); ksh93v is in the beta phase.
UnixWare 7 includes both ksh88 and ksh93. The default Korn shell is ksh93 supplied as /usr/bin/ksh, and the older version is available as /usr/bin/ksh88. UnixWare also includes dtksh when CDE is installed.
There are several software products related to KornShell:
- dtksh — a fork of ksh93, which is part of CDE.
- tksh — a fork of ksh93, which provides access to the Tk widget toolkit.
- oksh — a fork of OpenBSD′s flavour of KornShell, which supports GNU/Linux only; it is used as the default shell in DeLi Linux.
- mksh — a free implementation of the KornShell language, forked from pdksh, from MirOS BSD licensed under permissive (though not public domain) terms; specifically, the three-clause BSD License and the ISC License. Outside of BSD, this variant has replaced pdksh on Debian.
- SKsh — an AmigaOS flavour, which provides several Amiga-specific features, such as ARexx interoperability.
- MKS Inc.′s MKS Korn shell — a proprietary implementation of the KornShell language from Microsoft Windows Services for UNIX (SFU) up to version 2.0; according to David Korn, the MKS Korn shell was not fully compatible with KornShell in 1998. in SFU version 3.0 Microsoft replaced the MKS Korn shell with a new POSIX.2-compliant shell as part of Interix.
- KornShell is included in UWIN, a Unix compatibility package by David Korn.
- Ron Gomes (Jun 9, 1983). "Toronto USENIX Conference Schedule (tentative)". Newsgroup: net.usenix. Retrieved Dec 29, 2010.
- Guy Harris (Oct 10, 1983). "csh question". Newsgroup: net.flame. Retrieved Dec 29, 2010.
- Bolsky, Morris I.; Korn, David G. (1989). "Acknowledgements". The KornShell Command and Programming Language. Englewood Cliffs, NJ: Prentice Hall. pp. xii. ISBN 0-13-516972-0.
- Bill Rosenblatt; Arnold Robbins (2002). Learning the Korn Shell (2 ed.). O'Reilly Media, Inc. pp. viii–ix. ISBN 978-0-596-00195-7.
- J. Stephen Pendergrast (1995). Desktop KornShell graphical programming. Addison-Wesley. p. 359. ISBN 978-0-201-63375-7.
- Casey Cannon; Scott Trent; Carolyn Jones (1999). Simply AIX 4.3. Prentice Hall PTR. p. 21. ISBN 978-0-13-021344-0.
- "David Korn Tells All". Slashdot. Retrieved 2009-10-22.
- "Jerry Feldman — USENIX NT/LISA NT conference attendee". Lists.blu.org. Retrieved 2009-10-22.
- "Windows Services for UNIX Version 3.0". Technet.microsoft.com. Retrieved 2009-10-22.
- Anatole Olczak (2001). The Korn shell: Unix and Linux programming manual. Addison-Wesley Professional. p. 4. ISBN 978-0-201-67523-8.
- Morris I. Bolsky; David G. Korn (1995). The new KornShell command and programming language. Prentice Hall PTR. ISBN 978-0-13-182700-4.
- David G. Korn, Charles J. Northrup and Jeffery Korn The New KornShell—ksh93, Linux Journal, Issue 27, July 1996
- Korn shell home page (AT&T ksh)
- ksh93 man page
- ksh88 man page
- Public Domain Korn shell (pdksh)
- MirBSD Korn Shell (mksh)
- mksh man page (also as PDF in DIN A4 paper size)