Run command on docker image change

docker-check.sh

#!/bin/bash

set -eo pipefail

usage(){
  echo "Usage: docker-check image [command]"
  exit 1
}

version(){
  docker history -q $1 | head -n 1
  return 0
}

[ $# -eq 0 ] && usage

image=$1
shift 1


before=$(version $image)
docker pull $image 2>&1 > /dev/null
after=$(version $image)

if [ "$before" != "$after" ]; then
  "$@"
fi