A simple script to count the containers on a Docker host.

countContainers.sh

#!/bin/bash

function countContainers() {
	docker ps -q $1 | wc -l
}

function countCrashedContainers() {
	docker ps -a | grep -v -F 'Exited (0)' | grep -c -F 'Exited ('
}

TYPE=${1-all}

case $TYPE in
	running) COUNT_FUNCTION="countContainers"; shift;;
	crashed) COUNT_FUNCTION="countCrashedContainers"; shift;;
	all) COUNT_FUNCTION="countContainers -a"; shift;;
esac

$COUNT_FUNCTION