Versions of awk

The awk program was originally developed by Aho, Kernighan, and Weinberger in 1977 as a pattern-scanning language (the name “AWK” comes from their initials). Many new features have been added since then. The version of awk first implemented in UNIX System V, Release 3.1, added many features, such as additional built-in functions. In order to preserve compatibility with programs that were written for the original version, this one was named nawk (new awk). The use of two different commands for the two versions was a temporary step to provide time to convert programs using the older version to the new one. On some systems, including AIX, the awk command actually runs nawk.

On some Linux and UNIX systems, the awk command may actually run the gawk program. gawk is an enhanced, public domain version of awk that is part of the GNU system. It includes some new features and extensions, including the ability to do pattern matching that ignores the distinction between uppercase and lowercase.

For simplicity, this chapter refers to the language as awk and uses the command name awk in the examples. If you want to be sure which version of awk you are using, consult your system manual pages.