User-Defined Functions describes how to write your own
awk functions. Writing functions is
important, because it allows you to encapsulate algorithms and program tasks
in a single place. It simplifies programming, making program development
more manageable and making programs more readable.
In their seminal 1976 book, Software Tools, Brian Kernighan and P.J. Plauger wrote:
Good Programming is not learned from generalities, but by seeing how significant programs can be made clean, easy to read, easy to maintain and modify, human-engineered, efficient and reliable, by the application of common sense and good programming practices. Careful study and imitation of good programs leads to better writing.
In fact, they felt this idea was so important that they placed this statement on the cover of their book. Because we believe strongly that their statement is correct, this chapter and Chapter 11 provide a good-sized body of code for you to read and, we hope, to learn from.
This chapter presents a library of useful
awk functions. Many of the sample programs
presented later in this book use these functions. The functions are
presented here in a progression from simple to complex.
Extracting Programs from Texinfo Source Files presents a program that you can use to extract the source code for
these example library functions and programs from the Texinfo source for
this book. (This has already been done as part of the
The programs in ...