About 35 years ago, I did some embedded development on a 68k platform running OS-9 (ported to 68k from 6809). I was really impressed with the POSIX-like environment, but thoroughly disgusted with the very poor documentation. I found that I had to write a lot of stub code to fully determine and understand the behavior of the system calls.

This was after I had purchased and fully digested the only documentation I could find: "OS-9 Insights"

https://www.amazon.com/OS-9-insights-advanced-programmers-gu...