macOS command-line tools you might not know about

When mentioning `open` they should have noted that `open <file>` will open the given file with its associated app.

It’s indispensable.

Especially

    open .

if you need to drag a file somewhere. One thing that kind of breaks my muscle memory here is the opposite, something like

    firefox file.html

doesn't work and you have to fiddle with the arguments to get open to launch a non-default application.