Common Extensions (The GNU Awk User’s Guide)

From Get docs

A.7 Common Extensions Summary

The following table summarizes the common extensions supported by gawk, Brian Kernighan’s awk, and mawk, the three most widely used freely available versions of awk (see section Other Freely Available awk Implementations).

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