How to loop over Ansible variable names

user_4742108 0
Viewed 77

I'd like to find all variables with the myvar_ prefix and make a shell script that uses their names and contents.

---
- set_fact:
   myvar_a: "a"
   myvar_b: "b"
   myvar_c: "c"

- name: Format Django webapp parameters
  shell: |
    truncate -s0 out.txt
    {% for param in lookup('ansible.builtin.varnames', '^myvar_.+') %}
    echo {{ param }}  >> out.txt
    {% endfor %}

The output is:

m
y
v
a
r
_
a
,
m
y
v
a
r
_
b
,
m
y
v
a
r
_
c

It iterates a string character by character for some reason.

How to get variable names into out.txt?
How to get the contents of these variables to out.txt? (ok, it'll be {{ lookup("vars", param) }})

ansible jinja2
1 Answers

This happens because the lookup return you a comma separated list of variable names, not a list.

As demonstrated by the task:

- debug:
    var: lookup('ansible.builtin.varnames', '^myvar_.+')
  vars:
    myvar_a: a
    myvar_b: b
    myvar_c: c

Which yields:

ok: [localhost] => 
  lookup('ansible.builtin.varnames', '^myvar_.+'): myvar_a,myvar_b,myvar_c

There are three fixes possible:

  1. use the wantlist=true named argument of the lookup: 
    {% for param in lookup(
     'ansible.builtin.varnames', 
     '^myvar_.+', 
     wantlist=true
   ) 
%}
  2. use a query instead of a lookup, as query always returns a list: 
    {% for param in query(
     'ansible.builtin.varnames', 
     '^myvar_.+'
   ) 
%}
  3. split the string: 
    {% for param in lookup(
     'ansible.builtin.varnames', 
     '^myvar_.+'
   ).split(',') 
%}
user_21235300
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