Home / server / Questions / 1004989
Accepted
geets
Asked: 2020-02-29 07:22:05 +0800 CST

what does this jinja2 Filter do in Ansible? d({})

  • 772

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?

ansible jinja

1 Answers

  1. Best Answer

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

    A: d() is shortcut 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 fiter combine combines the dictionaries. Let's test it. For example

      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"
    }
    • 3