bash - How to check if the docker engine and a docker container are running?

Question

In a script, I need to check:

a) Is the docker engine running?
b) Given a container name, is that docker container running?

[the initial wording of this question was ambiguous, with some people interpreting it as "check docker engine", and others as "check docker container"]

Answer 1

If you are looking for a specific container, you can run:

if [ "$( docker container inspect -f '{{.State.Running}}' $container_name )" == "true" ]; then ...

To avoid issues with a container that is in a crash loop and constantly restarting from showing that it's up, the above can be improved by checking the Status field:

if [ "$( docker container inspect -f '{{.State.Status}}' $container_name )" == "running" ]; then ...

If you want to know if dockerd is running itself on the local machine and you have systemd installed, you can run:

systemctl show --property ActiveState docker

You can also connect to docker with docker info or docker version and they will error out if the daemon is unavailable.