Mounts Node node_modules directories within Vagrant so apps can run

mount_node_vagrant.rb

config.vm.provision "node_modules mounting", type: "shell", run: "always" do |shell|
  shell.privileged = false
  shell.args = "'#{app_name}'"
  shell.inline = <<-SHELL
  echo "Mounting node_modules directories"
    for directory in /$1/*; do
      if [ -f $directory/package.json ]; then
        mkdir -p $directory/node_modules
        mkdir -p /home/vagrant$directory/node_modules
        sudo mount --bind /home/vagrant$directory/node_modules $directory/node_modules
      fi
    done
  echo "Directories created"
  SHELL
end

What's '#{app_name}'
I am getting an error undefined local variable or method 'app_name'