The Unix V6 shell and how control flow worked in it

On Unix, ‘test‘ and ‘[‘ are two names for (almost) the same program and shell builtin. Although today people mostly use it under its ‘[‘ name, when it was introduced in V7 along side the Bourne shell, it only was called ‘test; the ‘[‘ name was only nascent until years later. I don’t know for sure why it was called ‘test‘, but there are interesting hints about its potential genesis in the shell used in V6 Research Unix, the predecessor to V7, and the control flow constructs that shell used.

↫ Chris Siebenmann

I’m fairly sure if I read this about 12 more times, I’ll start to maybe understand some of it.