Use dynamic variable name - ansible

Question

I'm trying to get the value of ip_address from the following yaml that I'm including as variables on ansible:
common:
ntp:
- time.google.com
node1:
default_route: 10.128.0.1
dns:
- 10.128.0.2
hostname: ip-10-128-5-17
device_interface: ens5
cluster_interface: ens5
interfaces:
ens5:
ip_address: 10.128.5.17
nat_ip_address: 18.221.63.178
netmask: 255.255.240.0
version: 2
However the network interface (ens5 here) may be named something else, such as eth0. My ansible code is this:
- hosts: all
tasks:
- name: Read configuration from the yaml file
include_vars: "{{ config_yaml }}"
- name: Dump Interface Settings
vars:
msg: node1.interfaces.{{ cvp_device_interface }}.ip_address
debug:
msg: "{{ msg }}"
tags: debug_info
Running the code like this I can get the key's name:
TASK [Dump Interface Settings] *************************************************
│ ok: [18.221.63.178] => {
│ "msg": "node1.interfaces.ens5.ip_address"
│ }
But what I actually need is the value (i.e: something like {{ vars[msg] }}, which should expand into {{ node1.interfaces.ens5.ip_address }}). How can I accomplish this?

Answer 1

Use sqare brackets.
Example: a minimal playbook, which defines a variable called "device". This variable is used to return the active status of the device.
- hosts: localhost
connection: local
vars:
device: enx0050b60c19af
tasks:
- debug: var=device
- debug: var=hostvars.localhost.ansible_facts[device].active
Output:
$ ansible-playbook example.yaml
[WARNING]: provided hosts list is empty, only localhost is available. Note that
the implicit localhost does not match 'all'
PLAY [localhost] *******************************************************************
TASK [Gathering Facts] *************************************************************
ok: [localhost]
TASK [debug] ***********************************************************************
ok: [localhost] => {
"device": "enx0050b60c19af"
}
TASK [debug] ***********************************************************************
ok: [localhost] => {
"hostvars.localhost.ansible_facts[device].active": true
}
PLAY RECAP *************************************************************************
localhost : ok=3 changed=0 unreachable=0 failed=0

Answer 2

see comment
- hosts: all
tasks:
- name: Read configuration from the yaml file
include_vars: "{{ config_yaml }}"
- name: Dump Interface Settings
debug:
msg: "{{ node1['interfaces'][cvp_device_interface]['ip_address'] }}"
debug:
msg: "{{ msg }}"
tags: debug_info