Ansible variable interpolation

Question

Clearly I am missing something (obvious?) here :-( Dictionary is correctly resolved as var in debug, but I can't get it into a message (msg). How do I trigger interpolation in this case correctly? (The actual usecase is not debug, but this is a most simple example I could construct).

---
- name: Setup based on subnet
  hosts: 
    - localhost
  vars:
    siteVars:
      10.128.0.0:
        ServerName:  "AServ"
      10.0.0.0:
        ServerName:  "BServ"
 
  tasks:
  - name: Do we get the right Network
    debug: 
      msg: "{{ ansible_default_ipv4.network }}"

  - name: Var works
    debug: 
      var: siteVars[ {{ 'ansible_default_ipv4.network' }} ].ServerName

  - name: Msg does not work interpolate
    debug:
       msg: "siteVars[ {{ 'ansible_default_ipv4.network' }} ].ServerName"

Gives:

TASK [Do we get the right Network] ******************************************************************************************ok: [localhost] => {
    "msg": "10.0.0.0"
}

TASK [Var works] ******************************************************************************************ok: [localhost] => {
    "siteVars[ ansible_default_ipv4.network ].ServerName": "BServ"
}

TASK [Msg does not work interpolate] ******************************************************************************************ok: [localhost] => {
    "msg": "siteVars[ ansible_default_ipv4.network ].ServerName"
}

U880D · Accepted Answer · 2022-01-09T13:00:49.650

1

How do I trigger interpolation in this case correctly?

Since siteVars and ServerName are part of the data structure (variable) too, the curly braces needs to surround them also.

- name: Msg work interpolate too
  debug:
    msg: "{{ siteVars[ansible_default_ipv4.network].ServerName }}"

Resulting into an output of

TASK [Msg work interpolate too] ***
ok: [localhost] =>
  msg: BServ

Other related questions here

Documentation

Ansible FAQ: When should I use {{ }}? How to interpolate variables or dynamic variable names?

edited Jan 09 '22 at 13:00

answered Jan 09 '22 at 12:39

U880D

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1

Note that, although a bit confusing for a beginner, the following option to `debug` works: `var: siteVars["{{ ansible_default_ipv4.network }}"].ServerName` – Zeitounator Jan 09 '22 at 13:00
Thanks a lot for getting me on the right track. Much appreciated. – user2179360 Jan 09 '22 at 18:53

Ansible variable interpolation

1 Answers1