Run the last command as the root user
We often see an error when executing a command that requires the root user permission. For example, installing a npm package as global probably requires
$ npm install -g package-name
In order to sudo the previous command, usually we press the Arrow key, append
`sudo` to the beginning of the command and run it again.
It turns out that there is an easier, shorter command:
`!!` references the last command.