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