KornShell

KornShell

Original author(s)	David Korn
Initial release	1983[1][2]
Stable release	ksh93v / June 1, 2013[3]
Development status	Active
Written in	C
Operating system	Unix
Available in	English
Type	Unix shell
License	AT&T KornShell: Eclipse Public License[4] pdksh: Public domain with some ISC-like code[5] mksh: MirOS Licence[6] dtksh: Eclipse Public License with some LGPL
Website	www.kornshell.org

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.

Design

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:

• Job control, command aliasing, and command history designed after the corresponding C shell features. Job control was added to the Bourne Shell in 1989.^[9]
• A choice of three command line editing styles based on vi, Emacs, and 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).

History

Interaction with OpenBSD's default shell, pdksh

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, 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 versions of the older ksh88 variant, 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.^[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 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.

Variants

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 Linux-based fork of OpenBSD's flavour of KornShell. It is used as the default shell in DeLi Linux.
• 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.^[17]
• 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.^[18][19] in SFU version 3.0 Microsoft replaced the MKS Korn shell with a new POSIX.2-compliant shell as part of Interix.^[20]
• KornShell is included in UWIN, a Unix compatibility package by David Korn.^[21]

See also

• Comparison of computer shells
• List of Unix utilities
• The test program

References

1. Ron Gomes (Jun 9, 1983). "Toronto USENIX Conference Schedule (tentative)". Newsgroup: net.usenix. Retrieved Dec 29, 2010.
2. Guy Harris (Oct 10, 1983). "csh question". Newsgroup: net.flame. Retrieved Dec 29, 2010.
3. http://www2.research.att.com/~astopen/download/notes.html
4. http://www2.research.att.com/~astopen/download/gen/ast-open.html
5. http://www.cs.mun.ca/~michael/pdksh/LEGAL
6. https://www.mirbsd.org/mksh.htm
7. 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.
8. 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.
9. http://www.in-ulm.de/~mascheck/bourne/#variants Bourne Shell evolvement
10. http://lists.research.att.com/pipermail/ast-users/2014q2/004548.html
11. Bill Rosenblatt; Arnold Robbins (2002). Learning the Korn Shell (2 ed.). O'Reilly Media, Inc. pp. viii–ix. ISBN 978-0-596-00195-7.
12. J. Stephen Pendergrast (1995). Desktop KornShell graphical programming. Addison-Wesley. p. 359. ISBN 978-0-201-63375-7.
13. Casey Cannon; Scott Trent; Carolyn Jones (1999). Simply AIX 4.3. Prentice Hall PTR. p. 21. ISBN 978-0-13-021344-0.
14. http://publib.boulder.ibm.com/infocenter/aix/v6r1/index.jsp?topic=/com.ibm.aix.cmds/doc/aixcmds5/sh.htm
15. http://publib.boulder.ibm.com/infocenter/aix/v6r1/index.jsp?topic=/com.ibm.aix.baseadmn/doc/baseadmndita/korn_shell_enhanced.htm
16. http://uw714doc.sco.com/en/DIFFS/UNIX95_Conformance.html#ksh-93_vs_ksh-88
17. https://people.debian.org/~spaillard/Debian_Release_Notes/mksh.html
18. "David Korn Tells All". Slashdot. Retrieved 2009-10-22.
19. "Jerry Feldman — USENIX NT/LISA NT conference attendee". Lists.blu.org. Retrieved 2009-10-22.
20. "Windows Services for UNIX Version 3.0". Technet.microsoft.com. Retrieved 2009-10-22.
21. Anatole Olczak (2001). The Korn shell: Unix and Linux programming manual. Addison-Wesley Professional. p. 4. ISBN 978-0-201-67523-8.

Further reading

• 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

External links

• Korn shell home page (AT&T ksh)
• github for AT&T open source software (AT&T research github)
• ksh93 man page at the Wayback Machine (archived June 5, 2013)
• ksh88 man page
• Public Domain Korn shell (pdksh)
• MirBSD Korn Shell (mksh)
• mksh(1) – MirOS BSD i386 General Commands Manual