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Interaction with OpenBSD's default shell, .mw-parser-output .monospaced{font-family:monospace,monospace}pdksh
Interaction with OpenBSD's default shell, pdksh
Original author(s)David Korn
Initial release1983; 38 years ago (1983)[1][2]
Stable release
u+ / August 1, 2012; 8 years ago (2012-08-01)[3]
Written inC
Operating systemUnix
Available inEnglish
TypeUnix shell

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.[1][2] The initial development was based on Bourne shell source code.[7] Other early contributors were Bell Labs developers Mike Veach and Pat Sullivan, who wrote the Emacs and vi-style line editing modes' code, respectively.[8] 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.) Major differences between KornShell and the traditional Bourne shell include:


Korn Shell running on Windows Services for UNIX

KornShell was originally proprietary software. In 2000 the source code was released under a license particular to AT&T, but since the 93q release in early 2005 it has been licensed under the Eclipse Public License.[4] 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, 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 versions of the older ksh88 variant, sometimes with extensions. ksh93 is maintained on GitHub.[10]

As "Desktop KornShell" (dtksh), ksh93 is distributed as part of the Common Desktop Environment.[11] This version also provides shell-level mappings for Motif widgets. It was intended as a competitor to Tcl/Tk.[12]

The original KornShell, ksh88, became the default shell on AIX in version 4,[13][14] with ksh93 being available separately.[15]

UnixWare 7 includes both ksh88 and ksh93. The default Korn shell is ksh93, which is supplied as /usr/bin/ksh, and the older version is available as /usr/bin/ksh88.[16] UnixWare also includes dtksh when CDE is installed.

The ksh93 distribution underwent a less stable fate after the authors left AT&T around 2012 at stable version ksh93u+. The authors continued working on a ksh93v- beta branch until around 2014, when a few community developers essentially "took over" and kept working to produce a heavily refactored "ksh2020".[17] In March 2020, AT&T decided to roll back the community changes, stash them in a branch, and restart from ksh93u+, as the changes were too broad and too ksh-focused for the company to absorb into a project in maintenance mode.[18][19] Debian offers ksh2020[20] in its testing version.[21]


There are several software products related to KornShell:

  • dtksh – a fork of ksh93 included as part of CDE.
  • tksh – a fork of ksh93 that provides access to the Tk widget toolkit.
  • oksh – a port of OpenBSD's flavour of KornShell, intended to be maximally portable[22] across operating systems. It was used as the default shell in DeLi Linux 7.2.
  • mksh – a free implementation of the KornShell language, forked from pdksh. It was originally developed for MirOS BSD and is licensed under permissive (though not public domain) terms; specifically, the MirOS Licence.[6] In addition to its usage on BSD, this variant has replaced pdksh on Debian,[23] and is the default shell on Android.
  • SKsh – an AmigaOS flavour that 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.[24][25] In SFU version 3.0 Microsoft replaced the MKS Korn shell with a new POSIX.2-compliant shell as part of Interix.[26]
  • KornShell is included in UWIN, a Unix compatibility package by David Korn.[27]

See also[edit]


  1. ^ a b Ron Gomes (Jun 9, 1983). "Toronto USENIX Conference Schedule (tentative)". Newsgroupnet.usenix. Retrieved Dec 29, 2010.
  2. ^ a b Guy Harris (Oct 10, 1983). "csh question". Newsgroupnet.flame. Retrieved Dec 29, 2010.
  3. ^ "ksh93u+date=10 February 2020". Retrieved 10 February 2020.
  4. ^ a b "Archived copy". Archived from the original on 2018-11-14. Retrieved 2018-12-10.CS1 maint: archived copy as title (link)
  5. ^ a b "MirBSD Korn Shell". Mirbsd.org. Retrieved 10 December 2018.
  6. ^ Korn, David G. (October 26, 1994), "ksh - An Extensible High Level Language", Proceedings of the USENIX 1994 Very High Level Languages Symposium, USENIX Association, retrieved February 5, 2015, Instead of inventing a new script language, we built a form entry system by modifying the Bourne shell, adding built-in commands as necessary.
  7. ^ 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.
  8. ^ "traditional Bourne shell family / history and development". In-ulm.de. Retrieved 10 December 2018.
  9. ^ "This is the AT&T Software Technology ast software download site from AT&T Research. The AT&T AST OpenSource Software Collection provides an overview and Practical Reusable UNIX Software." Github.com. 10 December 2018. Retrieved 10 December 2018.
  10. ^ Bill Rosenblatt; Arnold Robbins (2002). Learning the Korn Shell (2 ed.). O'Reilly Media, Inc. pp. viii–ix. ISBN 978-0-596-00195-7.
  11. ^ J. Stephen Pendergrast (1995). Desktop KornShell graphical programming. Addison-Wesley. p. 359. ISBN 978-0-201-63375-7.
  12. ^ Casey Cannon; Scott Trent; Carolyn Jones (1999). Simply AIX 4.3. Prentice Hall PTR. p. 21. ISBN 978-0-13-021344-0.
  13. ^ "IBM Knowledge Center". Ibm.com. Retrieved 10 December 2018.
  14. ^ "IBM Knowledge Center". Ibm.com. Retrieved 10 December 2018.
  15. ^ "UNIX95 conformance". Uw714doc.sco.com. Retrieved 10 December 2018.
  16. ^ "ksh2020 changelog". GitHub. 29 May 2020.
  17. ^ "Rewinding this repo and encouraging community · Issue #1466 · att/ast". GitHub.
  18. ^ "segfault with extended globs · #1464 · att/ast". GitHub.
  19. ^ "ksh2020 at GitHub". GitHub. 2 March 2020.
  20. ^ "Debian Package Tracker - ksh". tracker.debian.org.
  21. ^ "oksh at GitHub". GitHub. 1 August 2020.
  22. ^ "Archived copy". Archived from the original on 2014-07-28. Retrieved 2014-07-28.CS1 maint: archived copy as title (link)
  23. ^ "David Korn Tells All". Slashdot. Retrieved 2009-10-22.
  24. ^ "Jerry Feldman — USENIX NT/LISA NT conference attendee". Lists.blu.org. Retrieved 2009-10-22.
  25. ^ "Windows Services for UNIX Version 3.0". Technet.microsoft.com. Retrieved 2009-10-22.
  26. ^ Anatole Olczak (2001). The Korn shell: Unix and Linux programming manual. Addison-Wesley Professional. p. 4. ISBN 978-0-201-67523-8.

Further reading[edit]

External links[edit]