Unix Shell Programming — A 2-Day Course

 Open Public Course Closed In-House Course

Synopsis

This course is designed to give delegates practical experience in developing and writing shell scripts. Most of the built-in Korn shell commands are introduced together with the main program control structures.

The delegates will practise:

• Writing simple scripts to enhance basic command output
• Using the various shell quoting mechanisms appropriately
• Manipulating shell variables and user-defined variables in scripts
• Implementing conditional execution facilities
• Using the shell's built-in loop constructs where appropriate
• Writing scripts to trap user interrupts
• Developing menu-driven shell scripts

Course Objectives

On completion of the course the delegate will have a good working knowledge of how to manipulate the Shell as an environment interface and how to fully utilise the Shell programming language. This course uses the Korn Shell.

Suitable for

• Personnel who need to know the Shell programming language to be able to carry out their daily work
• Programmers, administrators and support personnel who need to understand existing shell scripts, automate procedures and write their own utilities

Prerequisites

• Completion of Unix Introduction course or equivalent knowledge
• Some programming experience may also prove advantageous

Publicly scheduled dates, locations, and prices

Contents:

Unix Command Review

• Basic Unix commands
• Filename generation characters
• Redirection and pipes

Getting Started

• What is a shell script?
• Development guidelines
• Creating and editing shell scripts
• Naming and storing shell scripts
• Executing shell scripts

Using Quotes

• Special characters
• Use of the backslash character
• Single and double quotes
• Backquotes - the command substitution character

Using Variables

• Environment variables
• User-defined variables
• The variable substitution character
• Manipulating and assigning values to variables
• Integer variables and the expr command

Handling Run Time Input

• Writing generic scripts
• User interaction and the read command
• Command line arguments and related variables
• The shift command

Condition Testing

• The if-then-elif-else statement
• Testing strings
• Integer tests
• Filename tests
• Exit status testing

Loop Constructs

• The while loop
• The until loop
• The for loop
• The while true and until false loops
• Loop control commands

Multi-Branch Decisions

• The case statement
• Patterns and actions
• Menu construction

Interrupt Handling

• Interrupt signals
• The trap command
• Abnormal termination of scripts

Additional Features and Facilities

• Scope of variables
• Default and substitute variables
• The && and || constructs
• Functions
• Background loops and loop redirection
• Here Documents