old_contents: var Docker = require('../lib/docker');
  var fs     = require('fs');
  
  var socket = process.env.DOCKER_SOCKET || '/var/run/docker.sock';
  var stats  = fs.statSync(socket);
  
  if (!stats.isSocket()) {
    throw new Error('Are you sure the docker is running?');
  }
  
  var docker = new Docker({ socketPath: socket });
  
  docker.listContainers({all: true}, function(err, containers) {
    console.log('ALL: ' + containers.length);
  });
  
  docker.listContainers({all: false}, function(err, containers) {
    console.log('!ALL: ' + containers.length);
  });
  
new_contents: var Docker = require('../lib/docker');
  var fs     = require('fs');
  
  var socket = process.env.DOCKER_SOCKET || '/var/run/docker.sock';
  var stats  = fs.statSync(socket);
  
  if (!stats.isSocket()) {
    throw new Error('Are you sure the docker is running?');
  }
  
  var docker = new Docker({ socketPath: socket });
  
  docker.listContainers({all: true}, function(err, containers) {
    console.log('ALL: ' + containers.length);
  });
  
  docker.listContainers({all: false}, function(err, containers) {
    console.log('!ALL: ' + containers.length);
  });
  
  // filter by labels
  var opts = {
    "limit": 3,
    "filters": '{"label": ["staging","env=green"]}'
  };
  
  docker.listContainers(opts, function(err, containers) {
    console.log('Containers labeled staging + env=green : ' + containers.length);
  });
  
subject: add filter by label string example