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A.6 Common Extensions Summary

This section summarizes the common extensions supported by gawk, Brian Kernighan's awk, and mawk, the three most widely-used freely available versions of awk (see Other Versions).

Feature BWK Awk Mawk GNU Awk
\x’ Escape sequence X X X
RS as regexp X X
FS as null string X X X
/dev/stdin special file X X
/dev/stdout special file X X X
/dev/stderr special file X X X
** and **= operators X X
fflush() function X X X
func keyword X X
nextfile statement X X X
delete without subscript X X X
length() of an array X X
BINMODE variable X X
Time related functions X X

(Technically speaking, as of late 2012, fflush(), ‘delete array’, and nextfile are no longer extensions, since they have been added to POSIX.)