I would like to have a shell script that checks if a particular container is running.
For example, I might want to start the container if it's not already running, or query some piece of information about it like what ports are exposed.
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2 Answers
The docker ps command takes a -f / --filter option to locate the desired container. To test if the container is running by name we might try
$ docker ps --filter "name=myapp" --filter "status=running"
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
91959ed76e77 foo/barbaz:latest "/init" 10 minutes ago Up 10 minutes myapp
If we just want the container ID, because we're going to pass it to another command like docker exec, we can use -q / --quiet:
$ docker ps --filter "name=myapp" --filter "status=running" --quiet
91959ed76e77
To just check whether it is running, we can see if the output is non-empty:
if [ -n "$(docker ps -f "name=myapp" -f "status=running" -q )" ]; then
echo "the container is running!"
fi
Or if we want some other piece of information about it, --format:
$ docker ps -f "name=myapp" -f "status=running" --format "{{.Image}}"
foo/barbaz:latest
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You might also try using the docker inspect command which works well with myapp as the container's name ... or the container's id :
if [ "$(docker inspect myapp --format '{{.State.Status}}')" = "running" ]; then
echo "the container is running!"
fi
