What does mkdir -p flag do?

Question

What does the mkdir -p flag do? i.e the '-p' part?

Answer 1

-p Will create nested directories, but only if they don't exist already.

For example: suppose you have a directory /foo already that you have write permissions for.

mkdir -p /foo/bar/baz  # creates bar and baz within bar under existing /foo

It is also an idempotent operation, because if you run the same command over again, you will not get an error, but nothing will be created.