To list all currently running docker containers run
docker ps
If no containers are running, this will give you this output:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
In case some containers are running, there will be additional lines listing the container like
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 1bd0a1461b38 bitnami/mariadb:latest "/entrypoint.sh /run…" 6 minutes ago Up 6 minutes 3306/tcp mydb