3

I try to understand what the following codeblock does inside an Ansible-Playbook

environment: '{{ inventory__environment | d({})
                   | combine(inventory__group_environment | d({}))
                   | combine(inventory__host_environment  | d({})) }}'

From my understanding the environment: Keyword sets environment variables on the target host. The double-moustaches {{ xxx }} mark a jinja2 expression - Correct me if Im wrong. So there happens some kind of evaluation of what is inside those brackets. An Expression of the following format {{ x | y }} is called a 'filter' in Ansible. It works like a pipe in Bash.

So what does this special function called d() do?

geets
  • 55

1 Answers1

4

Q: "What does this special function called d() do?"

A: d() is alias for default(). For example, the tasks below

    - set_fact:
        dictX: "{{ dict1 | d({})
                   | combine(dict2 | d({}))
                   | combine(dict3 | d({})) }}"
    - debug:
        var: dictX

,where dict1, dict2, and dict3 are not defined, give

    dictX: {}

The filter combine combines the dictionaries. Let's test it. For example,

- hosts: localhost

vars:


dict1:
  key1: value1



dict2:


key2: value2


dict3:
  key3: value3




tasks:


- set_fact:
    dictX: "{{ dict1 | d({})
               | combine(dict2 | d({}))
               | combine(dict3 | d({})) }}"
- debug:
    var: dictX

give

  dictX:
    key1: value1
    key3: value3
Vladimir Botka
  • 6,212