- name: Gather facts from host and print variables
  hosts: all
  gather_facts: yes
  tasks:

  - name: Print ansible facts
    tags: facts
    debug:
      var: ansible_facts

  - name: Print all variables
    tags: vars
    debug:
      var: vars

  - name: Print variable value
    tags: var
    when: var_name is defined
    debug:
      msg: "{{ var_name }}: {{ lookup('vars', var_name, default='undefined') }}"