Ansible: Insert line if not exists

Question

I\'m trying insert a line in a property file using ansible. I want to add some property if it does not exist, but not replace it if such property already exists in the file.

Answer 1

- name: add couchbase.host to properties, works like add or replace
  lineinfile: 
    state: present
    dest: /database.properties 
    regexp: '^couchbase.host'
    line: 'couchbase.host=127.0.0.1'