Shell Programming: Hands-On

Introduction and Overview

• Role of shell scripting
• Benefits of KornShell and Bash vs. other shells
• Differences and similarities between bash, ksh88 and ksh93
• Integrating scripts with external tools: grep, sed, awk and others
• Customising the login environment

Bash and KornShell Scripting Fundamentals

Shell script elements

• Commands and comments
• Defining exit values

Conditional program execution

• Applying if and case statements
• Simplifying if logic with elif

Program loops and iteration

• Conditional looping with while and until
• Listing for loops

Testing files and directories

• Analysing attributes
• Checking file size and contents

Strings and patterns using [[ ]]

• Comparing strings
• Verifying the existence of a string
• Pattern matching and special characters

Debugging

• Redirecting standard error
• set commands for debugging

Storing and Accessing Data

Positional parameters

• Passing and accessing parameters
• Setting and unsetting parameters
• Manipulating parameters as groups

Shell variables

• Defining environment and local variables
• Specifying default values and error conditions

Arrays

• Creating and indexing arrays
• Processing array contents with special variables

Processing Data

Manipulating strings

• Extracting substrings
• Determining string length
• Find and replace

Mathematics

• Arithmetic for and while loops
• Writing mathematical expressions: (( )), $(( )) and let

Modular Programming with Functions

Function basics

• Functions vs. scripts
• Parameters and variables

Creating a function library

• Finding your library with PATH
• Dot . and source commands

Interacting with the Outside World

Manipulating files and redirecting data

• Scripting file and directory management
• Deciphering redirection order
• Unravelling the secrets of exec: opening and closing multiple files

Interacting with running processes

• Handling errors
• Defining post-termination actions such as notification, cleanup
• Handling and sending signals: trap and kill

Accessing network servers

• Connecting to a network server
• Exchanging data with a network server

Creating "Production Quality" Scripts

Ensuring environmental control

• Checking and modifying environment variables
• Using getopts to process command line options

Handling user interactions

• Setting up error processing
• Employing select to create a menu interface
• Processing keyboard input