Ansible: using a variable in another variable declaration

Question

I'm stuck trying to use a variable in another variable declaration. Here is the code in my playbook:

- hosts: operate
  roles:
    - { role: dns, vargroup: 'test' }

- hosts: test
  roles:
    - common
    - certbot
    - ...

And now the very first lines of my dns role:

- debug: var=vargroup

- name: Extracting IP(s) {{vargroup}}
  vars:
    extractip: "{{ hostvars[groups['{{ vargroup }}'][0]]['ip'] }}"
  set_fact:
    newip: "{{ item.expose }}"
  with_items: 
    - '{{ extractip }}'

Vargroup is correclty printed in debug and my task name. But in the extractip part, i've got this error:

{
    "msg": "'dict object' has no attribute '{{ vargroup }}'",
    "_ansible_no_log": false
}

Obviously, i've try hardcoding the line like:

    extractip: "{{ hostvars[groups['test'][0]]['ip'] }}"

And it worked like a charm. I really don't know how to use this var in my var declaration :)

Tejas Sarade · Accepted Answer · 2020-04-17 21:06:55Z

1

This is probably caused by the way quotes works in YAML. After variable substitution '{{ extractip }}' will become '{{ hostvars[groups['{{ vargroup }}'][0]]['ip'] }}'. It will try to interprete '{{ vargroup }}' as a plain string instead of variable.

Just use double quotes and it will work

  with_items: 
    - "{{ extractip }}"

Since Ansible doesn't support nesting "{{ }}" construct, but you can simply remove that part and just use "{{ hostvars[groups[vargroup][0]]['ip'] }}".

edited Apr 17, 2020 at 21:06

answered Apr 17, 2020 at 13:09

Tejas Sarade

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5 Comments

djaunz Over a year ago

Hello, thank you for your help ! Unfortunately it is still not working :/

Tejas Sarade Over a year ago

Try this "{{ hostvars[groups[vargroup][0]]['ip'] }}"

djaunz Over a year ago

Worked ! Thank you :) Regarding this doc: docs.ansible.com/ansible/latest/reference_appendices/… I tried: extractip: "{{ hostvars[groups[{{ lookup('vars', 'vargroup') }}][0]]['ip'] }}" Do you know why it is not working ?

Zeitounator Over a year ago

Because, as explained above, you cannot nest jinja2 expression expansion markers (double curly braces). This would work: "{{ hostvars[groups[lookup('vars', 'vargroup')][0]]['ip'] }}". But that is not really following the KISS principle.

djaunz Over a year ago

Thank you guys ! I got it now :)

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