#!/bin/bash
# Get active containers
ACTIVE_CONTAINERS="$(docker ps -q --no-trunc 2>/dev/null)"

# Exit if no containers are active and return zero
if [ -z "${ACTIVE_CONTAINERS}" ]; then
  echo "0"
  exit
fi

# Get all relevant memory entries from containers
for container in ${ACTIVE_CONTAINERS} ; do
  CONT_MEMORY="$(cat /sys/fs/cgroup/docker/${container}/memory.stat 2>/dev/null | grep -Ew "anon|kernel|kernel_stack|pagetables|sec_pagetables|percpu|sock|vmalloc|shmem" | awk '{print $2}')"
  # Add up memory values
  for value in ${CONT_MEMORY} ; do
    if [[ ${value} =~ ^[0-9]+$ ]]; then
      ((MEMORY_USAGE += value))
    fi
  done
  unset CONT_MEMORY
done

# Check if value is a integer and return the value otherwiese return zero
if [[ ${MEMORY_USAGE} =~ ^[0-9]+$ ]]; then
  echo "${MEMORY_USAGE}"
else
  echo "0"
fi