### ksh overview

The KornShell language was designed and developed by David G. Korn at AT&T Bell Laboratories and AT&T Research. It is an interactive command language that provides access to the UNIX system and to many other systems, on the many different computers and workstations on which it is implemented. The KornShell language is also a complete, powerful, high-level programming language for writing applications, often more easily and quickly than with other high-level languages. This makes it especially suitable for prototyping. There are two other widely used shells, the Bourne shell developed by Steven Bourne at AT&T Bell Laboratories, and the C shell developed by Bill Joy at the University of California. ksh has the best features of both, plus many new features of its own. Thus ksh can do much to enhance your productivity and the quality of your work, both in interacting with the system, and in programming. ksh programs are easier to write, and are more concise and readable than programs written in a lower level language such as C.

The new version of ksh has the functionality of other scripting languages such as awk, icon, perl, rexx, and tcl. For this and many other reasons, ksh is a much better scripting language than any of the other popular shells. The code size for ksh is larger than the Bourne shell or C shell programs. The revised version is even larger.

In spite of its increased size, ksh provides better performance. You can write programs to run faster with ksh than with either the Bourne shell or the C shell, sometimes an order of magnitude faster. ksh has evolved and matured with extensive user feedback. It has been used by many thousands of people at AT&T since 1982, and at many other companies and universities. A survey conducted at one of the largest AT&T Bell Laboratories computer centers showed that 80% of their customers, both programmers and non-programmers, use ksh. ksh is compatible with the Bourne shell. Virtually all programs written for the Bourne shell run with ksh. If you are familiar with the Bourne shell, you can use ksh immediately, without retraining. The new version of ksh is compatible with earlier versions of ksh. ksh is readily available. It is sold (source and binary) by AT&T and Novell, and by other companies under license from AT&T both in the USA and abroad. It has been purchased by dozens of major corporations, and by many individuals for use on home computers. ksh is extensible.

The KornShell language uses the same syntax for built-in commands as for non built-in commands. Therefore, system developers can add new commands "transparently" to the KornShell language; that is, with minimum effort and with no differences visible to users other than faster execution. On systems with dynamic linking, it is possible to add new built-in commands at run time. Novell has extended the new version of ksh to enable X-windows programming for their desktop ksh product, dtksh. dtksh is a standard part of CDE, the Common Desktop Environment defined by COSE (Common Operating System Environment), supported by most major UNIX system hardware vendors. An extended version of ksh that enables Tk programming, called tksh, is available as well.

ksh is intended to conform to the Shell Language Standard developed by the IEEE POSIX 1003.2 Shell and Utilities Language Committee.

|  | March 13, 2012