Linux® Command Line and Shell Scripting Bible

Chapter 19. Advanced gawk

IN THIS CHAPTER

• Reexamining gawk

• Use variables in gawk

• Structured commands

• Format your printing

• Functions

Chapter 16 introduced the gawk program and demonstrated the basics of using it to produce formatted reports from raw data files. This chapter dives more deeply into customizing gawk to produce reports. The gawk program is a full-fledged programming language, providing features that allow you to write advanced programs to manipulate data. In this chapter, you'll see how to use the gawk programming language to write programs to handle just about any data formatting task you'll run into.

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

There are several built-in variables 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 16 demonstrated one type of built-in variable ...