Ancient History? RTFM

Just as our bodies have little, atavistic features that recapitulate our phylogeny, so does the shell. Back when dinosaurs roamed the earth, there was a shell called the "C shell" (cute name, eh?), that had a clumsy-but-complex history mechanism built around the ! key. Bash retains that mechanism, alongside its more modern one.

About the only useful thing left from it is !!, which means "redo the last command."

If you want to read about it, though, see the man page.

man bash

Impressive, huh?

I don't just mean the HISTORY EXPANSION section, which is 120 lines, starting around line 3172 on my machine. I mean the fact that the man page is over 3000 lines long. (Mine's close to 5000). There's a lot there.

It's usually easier to read a man page this big in a text editor, so stash a copy somewhere. Send it through col first, to remove funny characters.

man bash | col -b > /tmp/bash.man
vi /tmp/bash.man +/"^HISTORY EXPANSION"

On tomorrow, the seventh day, you should rest. The day after, I'll start to grade insensibly into more advanced topics: I'll talk a bit about processes, and how to handle them in the shell.