''gawk'' is GNU awk, the first free AWK implementation. ''gawk'' is compatible with nawk. ''gawk'' also adds several extensions to its language.

Many systems, and most GNU/Linux distros, use ''gawk'' as their default ''awk''. (Older BSD systems also used ''gawk'' as their default ''awk'', until newer BSD systems switched to ''nawk''.) ''gawk'' was the only free ''awk'', until the 1991 release of ''mawk''.

Gawkisms

A "gawkism" is an extension that works with ''gawk'', but not with other AWK variants. Gawk's own manual identifies GNU extensions, so programmers know which features require ''gawk''.

Some gawkisms are

  • GNU-style regular expressions.
  • extra built-in functions, like asort() and gensub().
  • Korn-style coprocesses.
  • TCP and UDP networking with "/inet/".
  • ''(since gawk 4.0.0)'' arrays of arrays, like ary[2][3] = 4.
  • ''(since gawk 4.0.0)'' indirect function calls, like str = "foo"; @str() # calls foo().
  • other GNU extensions in the manual.
  • Home page: [http://www.gnu.org/software/gawk/ gawk]
  • Manual: [http://www.gnu.org/software/gawk/manual/ ''Gawk: Effective AWK Programming'']