The Korn shell (ksh) is a Unix shell developed by David Korn (AT&T Bell Laboratories). It is compatible with the Bourne shell and includes many features of the C shell as well, such as a command history. For interactive use it provides the ability to edit the command line in a WYSIWYG fashion patterned after the vi and emacs editors. It also includes built-in arithmetic evaluation and advanced scripting functions similar to those used in more powerful programming languages such as awk, sed, and perl.
ksh aims to respect the Shell Language Standard (POSIX 1003.2 "Shell and Utilities Language Committee").
SKsh is an AmigaDOS-specific version and pdksh is a free Unix version.