How to Write Custom Ansible Filters?

let’s talk a bit about ansible filters.

A Simple Function or Set of Functions can transform a given input into the desired output.

Ansible Docs: docs.ansible.com/ansible/playbooks_filters.html

Create a folder called: filter_plugins

Create a .py file with any name: test.py with the below content.

import os
class FilterModule(object):
    def filters(self):
        return {'lastFolder': self.lastFolder}
    def lastFolder(self, path):
        if os.path.isdir(path):
            return path.split('/')[-1]
        else:
            return path.split('/')[-2]

please do keep in mind that Class Name & method filters should be there as exactly mentioned above otherwise it won’t work.

Create Sample Playbook to Test it: filter.yml

---
- hosts: localhost
  become: false
  gather_facts: false
  vars:
    - p1: /tmp/t1.txt
    - p2: /tmp/t2/
    - p3: /tmp/t3/t2/t1.txt
  tasks:
    - debug:
        msg: "{{ p1 | lastFolder }}"
    - debug:
        msg: "{{ p2 | lastFolder }}"
    - debug:
        msg: "{{ p3 | lastFolder }}"

Output from Playbook

Sample Structure of Folder

$ tree .
.
├── filter.yml
└── filter_plugins
    └── test.py
1 directory, 2 files

It is quite amazing that you can run native python 3 code for something if ansible can’t support it.

Hopefully, It will help you in the worse case!