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UNIX in a Nutshell: System V Edition

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4. The Bourne Shell and Korn Shell

This chapter presents the following topics:

  • Overview of features

  • Syntax

  • Variables

  • Arithmetic expressions (Korn shell only)

  • Command history (Korn shell only)

  • Job control

  • Invoking the shell

  • Restricted shells

  • Built-in commands

http://www.kornshell.com provides considerable information about the Korn shell. Follow the links there for binaries of ksh93 that can be downloaded for noncommercial and educational use. See also Learning the Korn Shell , which is listed in the Bibliography.

4.1 Overview of Features

The Bourne shell is the standard shell and provides the following features:

  • Input/output redirection

  • Wildcard characters (metacharacters) for filename abbreviation

  • Shell variables for customizing your environment

  • A built-in command set for writing shell programs

  • Job control (beginning in SVR4)

The Korn shell is a backward-compatible extension of the Bourne shell. Features that are valid only in the Korn shell are so indicated:

  • Command-line editing (using the command syntax of either vi or emacs )

  • Access to previous commands (command history)

  • Integer arithmetic

  • More ways to match patterns and substitute variables

  • Arrays and arithmetic expressions

  • Command-name abbreviation (aliasing)

  • More built-in commands

ksh93 adds the following capabilities:

  • Upwards compliance with POSIX

  • Internationalization facilities

  • An arithmetic for loop

  • Floating-point arithmetic and built-in arithmetic functions

  • Structured variable names and indirect variable references

  • Associative arrays

  • Even more ways to match patterns and substitute variables

  • Even more built-in commands

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