[TUHS] What was your "Aha, Unix!" moment?

[Bakul Shah]

On Sun, 20 Oct 2019 19:31:55 -0700 Ken Thompson via TUHS <tuhs at minnie.tuhs.org> wrote:
> i was writing the small utilities for the first
> pdp-11 unix. (rm ls date ....)
>
> so, cd was next.
>
> % pwd
> /usr/ken
> % cd /tmp
> % pwd
> /usr/ken
>
> Aha!

It was probably more like this:
% pwd
/usr/ken

?
Aha!