ansible/examples/playbooks/register_logic.yml

# here's a cool advanced topic about how to perform conditional logic in ansible without resorting
# to writing your own module that defines facts.  You can do that too, and it's easy to do, but
# often you just want to run a command and then decide whether to run some steps or not.  That's
# easy to do, and here we'll show you how.

- name: test playbook
  user: root
  hosts: all

  tasks:

      # it is possible to save the result of any command in a named register.  This variable will be made
      # available to tasks and templates made further down in the execution flow.  Here we save the result
      # of a simple 'cat' command in a variable called 'motd_contents'

      - action: shell cat /etc/motd
        register: motd_contents

      # and here we access the register.  Note that motd_contents as a variable is structured data because
      # it is a return from the command module.   The shell module makes available variables such as
      # as 'stdout', 'stderr', and 'rc'.  Here's a rather trivial example that runs an arbitrary step
      # if and only if the motd file contained the word 'hi'.   Remember that only_if statements are
      # Python expressions.  This is as complicated as Ansible syntax is going to get, and the only
      # time python really seeps into ansible's language.
 
      - action: shell echo "motd contains the word hi"
        only_if: "'${motd_contents.stdout}'.find('hi') != -1"