checking if a docker container is running

The following will return true if the container is running and false otherwise.

docker inspect -f {{.State.Running}} "$container_id"

The following fetches container id based on it's name,

name=alpine  
count=$(docker ps | grep "$name" | wc -l)  
if [ $count == 1 ]; then  
    id=$(docker ps | grep "$name" | cut -d ' ' -f 1)
    echo "$container_id"
elif [ $count == 0 ]; then  
    echo "No container with name $name"
else  
    echo "more than one container with name $name"
fi

note: In the above example we use docker ps and not docker ps -a. So, we can already assume that the containers it returns are in running state.