The first way that comes to mind is to use alias, e.g. `alias ipaddress="ipconfig getifaddr en0"`. Then running `ipaddress` would do what you want. To avoid having to run this again every time you log in, you can add the same line to your `~/.bash_profile`, which configures your shell when you log in before the initial command prompt. You can then type `source ~/.bash_profile` to reload your configuration without having to log out then back in.