Effective awk Programming, 4th Edition

Appendix A. The Evolution of the awk Language

This book describes the GNU implementation of awk, which follows the POSIX specification. Many longtime awk users learned awk programming with the original awk implementation in Version 7 Unix. (This implementation was the basis for awk in Berkeley Unix, through 4.3-Reno. Subsequent versions of Berkeley Unix, and, for a while, some systems derived from 4.4BSD-Lite, used various versions of gawk for their awk.) This chapter briefly describes the evolution of the awk language, with cross-references to other parts of the book where you can find more information.

To save space, we have omitted information on the history of features in gawk from this edition. You can find it in the online documentation.

Major Changes Between V7 and SVR3.1

The awk language evolved considerably between the release of Version 7 Unix (1978) and the new version that was first made generally available in System V Release 3.1 (1987). This section summarizes the changes, with cross-references to further details:

• The requirement for ‘;’ to separate rules on a line (see awk Statements Versus Lines)

• User-defined functions and the return statement (see User-Defined Functions)

• The delete statement (see The delete Statement)

• The do-while statement (see The do-while Statement)

• The built-in functions atan2(), cos(), sin(), rand(), and srand() (see Numeric Functions)

• The built-in functions gsub(), sub(), and match() (see String-Manipulation Functions)

• The built-in functions close() ...