Thinking that the BSDs have been left behind is to erroneously presume that the BSDs ran System 5 rc in the first place. They did not. Most of them use Mewburn rc (or their own reinvented version thereof), which was invented almost a decade after van Smoorenburg rc, which itself was invented about half a decade after System 5 rc.

Here's a "portable" script for van Smoorenburg rc that ports to 4 Linux families, complete with the sort of case statements that I described in https://news.ycombinator.com/item?id=10357589 :

* http://conman.googlecode.com/svn/trunk/etc/conman.init.in

Here's a Mewburn rc script:

* http://cvsweb.netbsd.org/bsdweb.cgi/~checkout~/src/etc/rc.d/...