The -p option in the bash history command?

Question

From man bash,

history -p arg [arg ...]

...

-p

Perform history substitution on the following args and display the result on the standard output.

What does 'history substitution' mean here? Can you provide an example of its use?

Thanks.

---

I understand command line history substitution, and already tried things like this:

history -p "!23:1"

But this is not dependent on -p, as xx "!23:1" does the same thing.

Answer 1

If you have history expansion enabled, and run history -p "!23:1", the expansion happens before the history builtin sees the designator !23:1, since history expansion takes place even within double-quotes.

However, if you either disable history expansion, or protect the exclamation mark with single quotes or a backslash, so that the builtin gets to handle it, you'll see that history -p outputs the result of that history expansion:

$ true
$ history -p '!!'
true

I assume the purpose of it is to be able to script history expansions.