Book Image

Linux Command Line and Shell Scripting Bible - Third Edition

By : Richard Blum, Christine Bresnahan
Book Image

Linux Command Line and Shell Scripting Bible - Third Edition

By: Richard Blum, Christine Bresnahan

Overview of this book

The Linux command line enables you to type specific shell commands directly into the system to manipulate files and query system resources. Command line statements can be combined into short programs called shell scripts, a practice increasing in popularity due to its usefulness in automation. Linux is a robust system with tremendous potential, and Linux Command Line and Shell Scripting Bible opens the door to new possibilities. Linux Command Line and Shell Scripting Bible is your essential Linux guide. It contains new functional examples that are fully updated to align with the latest Linux features. Beginning with command line fundamentals, the book moves into shell scripting and shows you the practical application of commands in automating frequently performed functions. This book is a complete guide providing detailed instruction and expert advice working within this aspect of Linux. Whether used as a tutorial or as a quick reference, this book contains information that every Linux user should know.
Table of Contents (34 chapters)
Part I: The Linux Command Line
Part II: Shell Scripting Basics
Part III: Advanced Shell Scripting
Part IV: Creating Practical Scripts
End User License Agreement

Using Variables

One important feature of any programming language is the ability to store and recall values using variables. The gawk programming language supports two different types of variables:

  • Built-in variables
  • User-defined variables

Several built-in variables are available for you to use in gawk. The built-in variables contain information used in handling the data fields and records in the data file. You can also create your own variables in your gawk programs. The following sections walk you through how to use variables in your gawk programs.

Built-in variables

The gawk program uses built-in variables to reference specific features within the program data. This section describes the built-in variables available for you to use in your gawk programs and demonstrates how to use them.

The field and record separator variables

Chapter 19 demonstrated one type of built-in variable available in gawk: the data field variables. The data field variables allow you to reference individual...