How to write dynamic variable in Ansible playbook

Question

Based on extra vars parameter I Need to write variable value in ansible playbook

ansible-playbook playbook.yml -e "param1=value1 param2=value2 param3=value3" 

If only param1 passed

myvariable: 'param1'   

If only param1,param2 passed

myvariable: 'param1,param2'  

If param1,param2,param3 are passed then variable value will be

myvariable: 'param1,param2,param3'  

When I try to create variable dynamically through template then my playbook always takes previous variable value. But inside dest=roles/myrole/vars/main.yml its writing correct value.

What I make a try here

- hosts: local   user: roop   gather_facts: yes   connection: local    tasks:     - template: src=roles/myrole/templates/myvar.j2 dest=roles/myrole/vars/main.yml    - debug: var=myvariable    roles:         - { role: myrole } 

So inside myrole directory I have created template and vars

- roles   - myrole     - vars/main.yml     - templates/myvar.j2  

templates/myvar.j2

{% if param1 is defined and param2 is defined and param3 is defined %}   myvariable: 'param1,param2,param3' {% elif param1 is defined and param2 is defined %}   myvariable: 'param1,param2' {% elif param1 is defined %}   myvariable: 'param1' {% else %}   myvariable: 'default-param' {% endif %}  

As I know if only two condition then I can do this using inline expression like below

{{ 'param1,param2' if param1 is defined and param2 is defined else 'default-param' }} 

<do something> if <something is true> else <do something else>

Is it possible if - elif - else in inline expression like above. Or any other way to assign value dynamically in ansible playbook?

Answer 1

I am sure there is a smarter way for doing what you want but this should work:

- name         : Test var   hosts        : all   gather_facts : no   vars:     myvariable : false   tasks:     - name: param1       set_fact:         myvariable: "{{param1}}"       when: param1 is defined      - name: param2       set_fact:         myvariable: "{{ param2 if not myvariable else myvariable + ',' + param2 }}"       when: param2 is defined      - name: param3       set_fact:         myvariable: "{{ param3 if not myvariable else myvariable + ',' + param3 }}"       when: param3 is defined      - name: default       set_fact:         myvariable: "default"       when: not myvariable      - debug:        var=myvariable 

Hope that helps. I am not sure if you can construct variables dynamically and do this in an iterator. But you could also write a small python code or any other language and plug it into ansible

Answer 2

my_var: the variable declared

VAR: the variable, whose value is to be checked

param_1, param_2: values of the variable VAR

value_1, value_2, value_3: the values to be assigned to my_var according to the values of my_var

my_var: "{{ 'value_1' if VAR == 'param_1' else 'value_2' if VAR == 'param_2' else 'value_3' }}"