Linux in a Nutshell, Fifth Edition

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Chapter 11: The gawk Programming Language

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

--source='program text'

Use program text as the awk source code. Use this option with -f to mix

command-line programs with awk library files.

--traditional

Disable all gawk-specific extensions, but allow common extensions (e.g., the

** operator for exponentiation).

--version

Print the version of gawk on standard error and exit.

Patterns and Procedures

awk scripts consist of patterns and procedures:

pattern { procedure }

Both pattern and { procedure } are optional. If pattern is missing, { procedure } is

applied to all lines. If { procedure } is missing, the matched line is printed.

Patterns

A pattern can be any of the following:

general expression

/regular expression/

relational expression

pattern-matching expression

BEGIN

END

• General expressions can be composed of quoted strings, numbers, operators,

function calls, user-defined variables, or any of the predefined variables

described later in this chapter in “Built-in Variables.”

• Regular expressions use the extended set of metacharacters, as described in

Chapter 7.

• The ^ and $ metacharacters refer to the beginning and end of a string (such

as the fields), respectively, rather than the beginning and end of a line. In par-

ticular, these metacharacters will not match at a newline embedded in the