Effective awk Programming, 3rd Edition

Appendix A. The Evolution of the awk Language

This book describes the GNU implementation of awk, which follows the POSIX specification. Many long-time 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 systems derived from 4.4BSD-Lite, use 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.

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 the Section 1.6 in Chapter 1).

• User-defined functions and the return statement (see the Section 8.2 in Chapter 8).

• The delete statement (see the Section 7.6 in Chapter 7).

• The do-while statement (see the Section 6.4.3 in Chapter 6).

• The built-in functions atan2, cos, sin, rand, and srand (see the Section 8.1.2 in Chapter 8).

• The built-in functions gsub, sub, and match (see the Section 8.1.3 in Chapter 8).

• The built-in functions close and system (see the Section 8.1.4 in Chapter 8).

• The ARGC, ARGV, FNR, RLENGTH, RSTART, and SUBSEP built-in variables ...