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.

strings are called associative arrays.

*

For example, to count the number of widgets

you have, you could use the following script:

/widget/ { count["widget"]++ } Count widgets

END { print count["widget"] } Print the count

You can use the special for loop to read all the elements of an associative array:

for (item in array)

process array[item]

The index of the array is available as item, while the value of an element of the

array can be referenced as array[item].

You can use the operator in to test that an element exists by testing to see if its

index exists. For example:

if (index in array)

...

tests that array[index] exists, but you cannot use it to test the value of the

element referenced by array[index].

You can also delete individual elements of the array using the delete statement.

(See also the delete entry in “Alphabetical Summary of awk Functions and

Commands,” later in this chapter.)

Escape sequences

Within string and regular-expression constants, the following escape sequences

may be used.

The \x escape sequence is a common extension; it is not part of

POSIX awk.

Octal and Hexadecimal Constants in gawk

gawk allows you to use octal and hexadecimal constants in your program source

code. The form is as in C: octal constants start with a leading ...