Print all variables for all hosts from the command line:

 $ ansible -i inventory/local -m debug -a "var=hostvars" all

Replace hostvars with any of the following to print:

• ansible_locals
• groups
• group_names
• environment
• vars
• ansible_sucks

Print all variables for all hosts from a playbook:

- hosts: all
  tasks:
    -  debug:
        var: hostvars[inventory_hostname]
        # -vvv to debug !!!!
        # verbosity: 4

Print all variables:

- name: print ansible_local
  debug: var=ansible_local