At the moment, it has most of the ksh88 features, not much of the ksh93 features, and a number of its own features. pdksh was initially created by Eric Gisin using Charles Forsyth's public domain V7 shell as a base as well as parts of the BRL shell. Since then a number of people have maintained and contributed to it

WWW: https://web.archive.org/web/20160918190548/http://www.cs.mun.ca/~michael/pdksh/
