wp-cli is a set of command-line tools for managing WordPress installations. You can update plugins, set up multisite installs, create posts and much more.
Once installed, you can run commands such as:
wp plugin install hello-dolly
which will output:
Installing Hello Dolly (1.5) Downloading install package from http://downloads.WordPress.org/plugin/hello-dolly.1.5.zip ... Unpacking the package ... Installing the plugin ... Plugin installed successfully.