How Does The Unix `history` Command Work?
As the day is winding down, I have a good hour just to myself. Perfect time to listen to some Billie Joel (it's either Billie Joel or Billie Eilish for me these days) and learn how the Unix history command works. Life is good.
I found this article (it's good etiquette nowadays to warn you that this is a Medium link) and it describes a bit of what's going on.
So let's see. We got a : followed by a timestamp followed by :0, then a separator (;) and finally the command itself. Each new command gets appended to the end of the file. Not too hard to recreate.
It turns out that shells like bash and zsh don't actually call a hook for history. Why should they? When history is a shell builtin, they can just track the commands internally.
Thankfully my editor-in-chief and resident Unix neckbeard Simon Brüggen explained that to me — but only after I sent him the first draft for this article. 😓
As such, the next section is a bit like Lord of the Rings: a sympathetic but naive fellow on a questionable mission with no clue of what he's getting himself into.
