KornShell#Variants

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{{cite web|url=https://www.in-ulm.de/~mascheck/bourne/|title=traditional Bourne shell family / history and development|website=In-ulm.de|access-date=10 December 2018}}
• a choice of three command line editing styles based on vi, Emacs, and Gosling Emacs
• associative arrays and built-in floating-point arithmetic operations (only available in the {{mono|ksh93}} version of KornShell)
• dynamic search for functions
• mathematical functions
• process substitution and process redirection
• C-language-like expressions
• enhanced expression-oriented {{mono|for}} and {{mono|while}} loops
• dynamic extensibility of (dynamically loaded) built-in commands (since {{mono|ksh93}})
• reference variables
• hierarchically nested variables
• variables can have member functions associated with them
• object-oriented-programming (since {{mono|ksh93t}})
• variables can be objects with member (sub-)variables and member methods
• object methods are called with the object variable name followed (after a dot character) by the method name
• special object methods are called on: object initialization or assignment, object abandonment ({{mono|unset}})
• composition and aggregation is available, as well as a form of inheritance

File:Korn Shell running on SUA.png]]

KornShell was originally proprietary software. In 2000 the source code was released under a license particular to AT&T, but since the ksh93q release in early 2005 it has been licensed under the Eclipse 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 {{mono|pdksh}}, {{mono|mksh}}, Bash, and Z shell.

The functionality of the original KornShell, {{mono|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 {{mono|ksh88}} variant, sometimes with extensions. {{mono|ksh93}} is maintained on GitHub.{{cite web|url=https://github.com/att/ast|title=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..|date=10 December 2018|access-date=10 December 2018|website=Github.com}}

As "Desktop KornShell" ({{mono|dtksh}}), {{mono|ksh93}} is distributed as part of the Common Desktop Environment.{{cite book|author1=Bill Rosenblatt|author2=Arnold Robbins|title=Learning the Korn Shell|url=https://books.google.com/books?id=5nMCY272chUC&pg=PR8|year=2002|publisher=O'Reilly |isbn=978-0-596-00195-7|pages=viii–ix|edition=2}} This version also provides shell-level mappings for Motif widgets. It was intended as a competitor to Tcl/Tk.{{cite book|first=J. Stephen |last=Pendergrast|title=Desktop KornShell graphical programming|url=https://books.google.com/books?id=O6xQAAAAMAAJ|year=1995|publisher=Addison-Wesley|isbn=978-0-201-63375-7|page=359}}

The original KornShell, {{mono|ksh88}}, became the default shell on AIX in version 4,{{cite book|author1=Casey Cannon|author2=Scott Trent|author3=Carolyn Jones|title=Simply AIX 4.3|year=1999|publisher=Prentice Hall |isbn=978-0-13-021344-0|page=21}}{{cite web|url=https://www.ibm.com/support/knowledgecenter/ssw_aix_61/eos/eos.htm?origURL=api/redirect/aix/v6r1/topic/com.ibm.aix.cmds/doc/aixcmds5/sh.htm|title=IBM Knowledge Center|publisher=IBM|access-date=10 December 2018}} with ksh93 being available separately.{{cite web|url=https://www.ibm.com/support/knowledgecenter/ssw_aix_61/eos/eos.htm?origURL=api/redirect/aix/v6r1/topic/com.ibm.aix.baseadmn/doc/baseadmndita/korn_shell_enhanced.htm|title=IBM Knowledge Center|publisher=IBM|access-date=10 December 2018}}

UnixWare 7 includes both {{mono|ksh88}} and {{mono|ksh93}}. The default Korn shell is {{mono|ksh93}}, which is supplied as {{mono|/usr/bin/ksh}}, and the older version is available as {{mono|/usr/bin/ksh88}}.{{cite web|url=http://uw714doc.sco.com/en/DIFFS/UNIX95_Conformance.html#ksh-93_vs_ksh-88|title=UNIX95 conformance|website=Uw714doc.sco.com|access-date=10 December 2018}} UnixWare also includes {{mono|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 primary authors continued working on a ksh93v- beta branch until around 2014. That work was eventually taken up primarily by Red Hat in 2017 (due to customer requests) and resulted in the eventual initial release of ksh2020{{cite web |title=ksh2020 |url=https://github.com/ksh2020/ksh |website=GitHub |date=26 Feb 2021 |language=en}} in the fall of 2019. That initial release (although fixing several prior stability issues) introduced breakage and compatibility issues.{{cite web |title=ksh2020 changelog |url=https://github.com/att/ast/blob/ksh2020/CHANGELOG.md |website=GitHub |date=29 May 2020 |language=en}} 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.{{cite web |title=Rewinding this repo and encouraging community · Issue #1466 · att/ast |url=https://github.com/att/ast/issues/1466 |website=GitHub |language=en}}{{cite web |title= segfault with extended globs · #1464 · att/ast |url=https://github.com/att/ast/issues/1464#issuecomment-581159703 |website=GitHub |language=en}} ksh2020 {{Cite web|title= 2020.0.0: Stable release of ksh-2020.0.0 |url=https://github.com/att/ast/releases/tag/2020.0.0|access-date=2021-01-29|quote=Note: ksh2020 is not maintained or supported|website=GitHub|language=en}} was released as a "major release for several reasons"{{Cite web|title=ksh 2020.0.0 CHANGELOG|url=https://github.com/att/ast/blob/2020.0.0/CHANGELOG.md |date=2021-01-29|website=GitHub|language=en}} such as removal of EBCDIC support, dropping support for binary plugins written for ksh93u+ and removal of some broken math functions, but has never been maintained or supported by AT&T (not even on its initial release date). The ksh2020 source code has received no commits since February 2020 and it was archived read only in October 2021.

Following the issues with the ksh2020 branch and its abandonment, a new repository was created in May 2020 for the ksh93u+m branch, based on the last stable AT&T release (ksh93u+ 2012-08-01) where bugfix development actively continues.{{cite web |title=ksh 93u+m |url=https://github.com/ksh93/ksh |website=GitHub|date=17 November 2021 }}

For the purposes of the lists below, the main software branch of KSH is defined as the original program, dating from July 1983, up and through the release of KSH2020 in late 2019.

Continuing development of follow-on versions (branches) of KSH have split into different groups starting in 2020 and are not elaborated on below.

The following are listed in a roughly ascending chronological order of their contributions:

• David G. Korn (AT&T Bell Laboratories, AT&T Laboratories, and Google; and creator)
• Glenn S. Fowler (AT&T Bell Laboratories, AT&T Laboratories)
• Kiem-Phong Vo (AT&T Bell Laboratories, AT&T Laboratories)
• Adam Edgar (AT&T Bell Laboratories)
• Michael T. Veach (AT&T Bell Laboratories)
• Patrick D. Sullivan (AT&T Bell Laboratories)
• Matthijs N. Melchior (AT&T Network Systems International)
• Karsten-Fleischer (Omnium Software Engineering)
• Boyer-Moore
• Siteshwar Vashisht (Red Hat)
• Kurtis Rader

• Roland Mainz

The following are listed in a roughly ascending chronological order of their contributions:

• AT&T Bell Laboratories
• AT&T Network Systems International
• AT&T Laboratories (now AT&T Labs)
• Omnium Software Engineering
• Oracle Corporation
• Google
• Red Hat

Besides the primary major contributing corporations (listed above), some companies have contributed free resources to the development of KSH. These are listed below (alphabetically ordered):

• Coverity
• GitHub
• Travis CI

There are several forks and clones of KornShell:

• {{mono|dtksh}} – a fork of {{mono|ksh93}} included as part of CDE.
• {{mono|tksh}} – a fork of {{mono|ksh93}} that provides access to the Tk widget toolkit.
• {{mono|oksh}} – a port of OpenBSD's variant of KornShell, intended to be maximally portable{{cite web |title=oksh at GitHub|url=https://github.com/ibara/oksh/blob/master/README.md |website=GitHub |date=1 August 2020 |language=en}} across operating systems. It was used as the default shell in DeLi Linux 7.2.
• {{mono|loksh}} – a Linux port of OpenBSD's variant of KornShell, with minimal changes.{{cite web |title=loksh at GitHub|url=https://github.com/dimkr/loksh/blob/master/README.md |website=GitHub |date=15 October 2021 |language=en}}
• {{mono|mksh}} – a free implementation of the KornShell language, forked from OpenBSD {{mono|pdksh}}. It was originally developed for MirOS BSD and is licensed under permissive (though not public domain) terms; specifically, the MirOS Licence. In addition to its usage on BSD, this variant has replaced {{mono|pdksh}} on Debian,{{Cite web |url=https://people.debian.org/~spaillard/Debian_Release_Notes/mksh.html |title=5.11. The PDKSH to MKSH transition |access-date=2014-07-28 |archive-url=https://web.archive.org/web/20140728110151/https://people.debian.org/~spaillard/Debian_Release_Notes/mksh.html |archive-date=2014-07-28 |url-status=dead }} and is the default shell on Android.
• {{mono|SKsh}} – an AmigaOS variant that provides several Amiga-specific features, such as ARexx interoperability.{{Cite web|url=http://aminet.net/package/util/shell/SKsh21|title = Aminet - util/Shell/SKsh21.LZH}} In this tradition MorphOS uses {{mono|pdksh}} in its SDK.
• 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.{{cite web|url=http://slashdot.org/articles/01/02/06/2030205.shtml |title=David Korn Tells All |date=7 February 2001 |publisher=Slashdot |access-date=2009-10-22}}{{cite web|url=http://lists.blu.org/pipermail/discuss/1998-August/002393.html |title=Jerry Feldman — USENIX NT/LISA NT conference attendee |date=29 August 1998 |publisher=Lists.blu.org |access-date=2009-10-22}} In SFU version 3.0 Microsoft replaced the MKS Korn shell with a new POSIX.2-compliant shell as part of Interix.{{cite web|url=https://technet.microsoft.com/de-de/library/bb463204(en-us).aspx |title=Windows Services for UNIX Version 3.0 |date=5 December 2007 |publisher=Technet.microsoft.com |access-date=2009-10-22}}
• KornShell is included in UWIN, a Unix compatibility package by David Korn.{{cite book|author=Anatole Olczak|title=The Korn shell: Unix and Linux programming manual|url=https://books.google.com/books?id=dCIJv94vXUMC&pg=PA4|year=2001|publisher=Addison-Wesley Professional|isbn=978-0-201-67523-8|pages=4}}
• {{mono|/bin/sh}} in Doug Gwyn's (US Army BRL) System V on BSD package included Ron Natalie's version of the SVR2 {{mono|/bin/sh}} that had both job control and command line editing. This was a contemporary of the original {{mono|ksh}} at a time when it had not escaped AT&T. This was subsequently the {{mono|/bin/sh}} that shipped with all the CMU Mach-derived systems.{{cite web

| url=https://tuhs.org/mailman3/hyperkitty/list/tuhs@tuhs.org/thread/L6YV554T3DNXIKKUPKX2UFC473TT7B6E/

| url-status=live

| title="Job Control and other terminal fun"

| first=Ron

| last=Natalie

| date=2023-01-30

| others=From the TUHS ("The Unix Heritage Society") mailing list

| quote=... The Berkeley job control was an interesting hack. For us at BRL the problem was I absolutely detested the C shell syntax. The Korn shell hadn’t escaped from AT&T yet, so, I spent time figuring out how that really worked in the C shell (not really well documented), mostly by inspection, and then reimplemented it in the Bourne Shell (we were using the System V source code version for that). I still couldn’t get traction at BRL for using the Bourne shell because by that time, tcsh had come out with command line editing. So back to the shell sources I went. By this time, 5R2 had come out so I grabbed the shell source form[sic] that. [...] I reworked emacs-ish command line editing into the shell. Subsequently, I had a nice conversation with David Korn at USENIX, being probably at that point the two most familiar with Bourne shell job control internals. I also sat down with the guys writing either bash or the pdksh (can’t remember which) and explained all how this work[sic]. ... Years later I, had left the BRL, spent three years as a Rutgers administrator and was working for a small startup in Virginia. There was a MIPS workstation there. I was slogging along using ed... Not thinking about it, I attempted to retrieve a backgrounded job by typing “fg.” To my surprise the shell printed “Job control not enabled.” Hmm, I say. That sounds like my error message. “set -J” I type. “Job control enabled.” Hey! This is my shell. Turns out Doug Gwyn put my mods into his “System V on BSD” distribution tape and it had made its way into the Mach code base and so every Mach-derived system ended up with it.

| access-date=2024-07-07

| archive-url=https://web.archive.org/web/20240707205154/https://www.tuhs.org/mailman3/hyperkitty/list/tuhs@tuhs.org/thread/L6YV554T3DNXIKKUPKX2UFC473TT7B6E/

| archive-date=2024-07-07

}}

{{Portal|Free and open-source software}}

• Comparison of computer shells
• List of Unix commands
• test (Unix)

{{Reflist|30em}}

• {{cite book|author1=Morris I. Bolsky|author2=David G. Korn|title=The new KornShell command and programming language|year=1995|publisher=Prentice Hall PTR|isbn=978-0-13-182700-4|url=https://archive.org/details/newkornshellcomm00bols}}
• {{cite journal

|author1=David G. Korn

|author2=Charles J. Northrup

|author3=Jeffery Korn

|url=http://www.linuxjournal.com/article/1273

|url-status=live

|title=The New KornShell—ksh93

|journal=Linux Journal

|number=27

|date=July 1996

|archive-date=2015-10-11

|archive-url=https://archive.today/20151011155538/http://www.linuxjournal.com/article/1273

}}

• {{webarchive |url=https://web.archive.org/20130605160033/http://www.research.att.com/~gsf/man/man1/ksh.html |date=June 5, 2013 |title=ksh93 man page }}
• {{webarchive |url=https://web.archive.org/20151105130220/http://www2.research.att.com/sw/download/man/man1/ksh88.html |date=November 5, 2015 |title = ksh88 man page}}
• {{webarchive |url=https://web.archive.org/20161021105605/http://web.cs.mun.ca/~michael/pdksh/ |date=October 21, 2016 |title=Public Domain Korn shell (pdksh)}}
• [http://www.mirbsd.org/mksh.htm MirBSD Korn Shell (mksh)]
• {{man|1|mksh|MirOS BSD}}

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