Summary of Korn Shell Features

The Korn shell is the most advanced of the shells that are "officially" distributed with UNIX systems. It's a backward-compatible evolutionary successor to the Bourne shell that includes most of the C shell's major advantages as well as a few new features of its own.

Features appropriated from the C shell include:

• Job control , including the fg and bg commands and the ability to stop jobs with CTRL-Z.

• Aliases , which allow you to define shorthand names for commands or command lines.

• Functions (included in some C shell versions), which increase programmability and allow you to store your own shell code in memory instead of files.

• Command history , which lets you recall previously entered commands.

The Korn shell's major new features include:

• Command-line editing , allowing you to use vi or emacs -style editing commands on your command lines.

• Integrated programming features : the functionality of several external UNIX commands, including test , expr , getopt , and echo , has been integrated into the shell itself, enabling common programming tasks to be done more cleanly and without creating extra processes.

• Control structures , especially the select construct, which enables easy menu generation.

• Debugging primitives that make it possible to write tools that help programmers debug their shell code.

• Regular expressions , well known to users of UNIX utilities like grep and awk , have been added to the standard set of filename wildcards and to the shell variable facility.

• Advanced I/O features , including the ability to do two-way communication with concurrent processes (coroutines ).

• New options and variables that give you more ways to customize your environment.

• Increased speed of shell code execution.

• Security features that help protect against "Trojan horses" and other types of break-in schemes.