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

Looks like it does not work if you use backrefs.

Following sample does not add a line

- name: add hosts file entry
  lineinfile:
    path: "/etc/hosts"
    regexp: "foohost"
    line:  "10.10.10.10 foohost"
    state: present
    backrefs: yes

After removing backrefs I got my line added to the file

- name: add hosts file entry
  lineinfile:
    path: "/etc/hosts"
    regexp: "foohost"
    line:  "10.10.10.10 foohost"
    state: present

Answer 2

By a long way of "Trials and errors" I come to this:

- name: check existence of line in the target file
  command: grep -Fxq "ip addr add {{ item }}/32 dev lo label lo:{{ app | default('app') }}" /etc/rc.local
  changed_when: false
  failed_when: false
  register: ip_test
  with_items:
    - "{{ list_of_ips }}"

- name: add autostart command
  lineinfile: dest=/etc/rc.local 
              line="ip addr add {{ item.item }}/32 dev lo label lo:{{ app | default('app') }}"
              insertbefore="exit 0"
              state=present
  when: item.rc == 1
  with_items:
    - "{{ ip_test.results }}"

Answer 3

We have tried the below and it worked well. our scenario need to entry "compress" in syslog file if it does not exist.

- name: Checking compress entry present if not add entry   
  lineinfile:
    path: /etc/logrotate.d/syslog
    regexp: "    compress"
    state: present
    insertafter: "    missingok"
    line: "    compress"

Answer 4

- 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'