Command line WiFi Access in Linux

One of our computers has been installed with a very barebones version of Ubuntu, as such there’s no GUI way to set the wireless so I need to know the command line commands:

iwconfig – configures wireless network interface including specific wireless interface
iwlist [interface] scanning – lists available wireless nodes
iwconfig [interface] essid [essid] – sets wireless point to connect to
sudo dhclient [interface] – DHCP get IP address.