Command completion is not working for me. I followed the steps to the T but getting this output in the final step.
P-M-M1GB:~ JHSbDa6E$ etc=/Applications/Docker.app/Contents/Resources/etc
P-M-M1GB:~ JHSbDa6E$ ln -s $etc/docker.bash-completion $(brew --prefix)/etc/bash_completion.d/docker
ln: /usr/local/etc/bash_completion.d/docker: File exists
P-M-M1GB:~ JHSbDa6E$ ln -s $etc/docker-machine.bash-completion $(brew --prefix)/etc/bash_completion.d/docker-machine
ln: /usr/local/etc/bash_completion.d/docker-machine: File exists
P-M-M1GB:~ JHSbDa6E$ ln -s $etc/docker-compose.bash-completion $(brew --prefix)/etc/bash_completion.d/docker-compose
ln: /usr/local/etc/bash_completion.d/docker-compose: File exists