code used in conjunction with book
http://wiki.ros.org/melodic/Installation/Ubuntu
sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -sc) main" > /etc/apt/sources.list.d/ros-latest.list'
sudo apt-key adv --keyserver hkp://ha.pool.sks-keyservers.net:80 --recv-key 421C365BD9FF1F717815A3895523BAEEB01FA116
sudo apt-get update
sudo apt install ros-melodic-desktop-full
initialise ROS
sudo rosdep init
rosdep update
๐