I was following instructions (https://docs.docker.com/engine/installation/linux/docker-ce/ubuntu/#install-docker-ce-1) to try install Docker CE on VirtualBox running Ubuntu 16.04.3. Then when I tried to set up the stable repository on step 4 by doing:
sudo add-apt-repository \ "deb [arch=amd64] https://download.docker.com/linux/ubuntu \ $(lsb_release -cs) \ stable"
Error: 'deb [arch=amd64] https://download.docker.com/linux/ubuntu \ xenial \ stable' invalid
Can someone please help? I am new to programming but online search doesn't appear to show anything directly relevant.