History summary (The GNU Awk User’s Guide)

The awk language has evolved over time. The first release was with V7 Unix, circa 1978. In 1987, for System V Release 3.1, major additions, including user-defined functions, were made to the language. Additional changes were made for System V Release 4, in 1989. Since then, further minor changes have happened under the auspices of the POSIX standard.
Brian Kernighan’s awk provides a small number of extensions that are implemented in common with other versions of awk.
gawk provides a large number of extensions over POSIX awk. They can be disabled with either the --traditional or --posix options.
The interaction of POSIX locales and regexp matching in gawk has been confusing over the years. Today, gawk implements Rational Range Interpretation, where ranges of the form ‘[a-z]’ match only the characters numerically between ‘a’ through ‘z’ in the machine’s native character set. Usually this is ASCII, but it can be EBCDIC on IBM S/390 systems.
Many people have contributed to gawk development over the years. We hope that the list provided in this chapter is complete and gives the appropriate credit where credit is due.