As you have already seen, each awk statement consists of
a pattern with an associated action. This chapter describes how
you build patterns and actions, what kinds of things you can do within
actions, and awk’s predefined variables.
The pattern–action rules and the statements available for use
within actions form the core of awk programming.
In a sense, everything covered
up to here has been the foundation
that programs are built on top of. Now it’s time to start
building something useful.