It's been a few years since I was a sysadmin, but I believe either his DNS system or qmail system will show it. When I first read them, I thought they were very annoying, because it's not one monolithic program, and there are a lot of one-line shell scripts that do sequential operations using exec. The way he describes it, he's getting rid of a lot of parsing by using the directory tree instead of text files following. But this use of directories can also be good for some of the more degenerate uses of databases. Mostly I recall the "aha" moment of "So, this is the Unix philosophy in action." The design is very elegant.