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| Chapter 4 |

# 4. The Bourne Shell and Korn Shell

Contents:
Overview of Features
Syntax
Variables
Arithmetic Expressions
Command History
Built-in Commands (Bourne and Korn Shell)
Job Control
Invoking the Shell
Restricted Shells

This section presents the following topics:

- Overview of features

- Syntax

- Variables

- Arithmetic expressions (Korn shell only)

- Command history (Korn shell only)

- Built-in commands

- Job control

- Invoking the shell

- Restricted shells

## 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 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).

3.5 Differing Features |  | 4.2 Syntax