You can't trust code that you did not totally create yourself. (Especially code from companies that employ people like me.) No amount of source-level… - Ken Thompson

I think the major good idea in Unix was its clean and simple interface: open, close, read, and write.

I would try out the [C++] language [at AT&T] as it was being developed and make comments on it. It was part of the work atmosphere there. And you'd write something and then the next day it wouldn't work because the language changed. It was very unstable for a very long period of time. At some point, I said, no, no more. In an interview I said exactly that, that I didn't use it because it wouldn't stay still for two days in a row. When Stroustrup read the interview he came screaming into my room about how I was undermining him and what I said mattered and I said it was a bad language.

grep was a private command of mine for quite a while before i made it public.