Developing Advanced Automation with Red Hat Ansible Automation Platform

Ansible uses the file plug-in to load the contents of a local file into a variable. If you provide a relative path, the plug-in looks for files in the playbook's files directory.

The following example reads the contents of the user's public key file and uses the ansible.posix.authorized_key module to add the authorized key to the managed host. The example uses a loop and the + operator to append strings in the template to look up the files/fred.key.pub and files/naoko.key.pub files.

- name: Add authorized keys
  hosts: all
  vars:
    users:
      - fred
      - naoko
  tasks:
    - name: Add authorized keys
      ansible.posix.authorized_key:
        user: "{{ item }}"
        key: "{{ lookup('ansible.builtin.file', item + '.key.pub') }}"
      loop: "{{ users }}"

The file plug-in can parse YAML and JSON files into properly structured data by using the from_yaml or from_json filters.

my_yaml: "{{ lookup('ansible.builtin.file', '/path/to/my.yaml') | from_yaml }}"

- name: Collect file content
  ansible.builtin.slurp:
    src: /home/user/.ssh/id_rsa.pub
  register: slurped_file

- name: Print returned information
  vars:
    pub_key: "{{ slurped_file['content'] | b64decode }}"
  ansible.builtin.debug:
    var: pub_key

Like the file plug-in, the template plug-in returns the contents of files. The difference is that the template plug-in expects the file contents to be a Jinja2 template, and it evaluates that template before applying the contents. If you pass a relative path to the template file, the plug-in looks for it within the playbook templates directory.

The following example processes the templates/my.template.j2 template.

{{ lookup('ansible.builtin.template', 'my.template.j2') }}

For example, assume that the template contains the following content:

Hello {{ name }}.

The following task displays the string "Hello class.".

- name: Print "Hello class."
  vars:
    name: class
  ansible.builtin.debug:
    msg: "{{ lookup('ansible.builtin.template', 'my.template.j2') }}"

The template plug-in also accepts some extra parameters, such as defining the start and end marking sequences. In case the output string is a YAML value, the convert_data option parses the string to provide structured data.

The pipe and lines plug-ins both run a command in the execution environment and return the output. The pipe plug-in returns the raw output generated by the command; the lines plug-in splits the output of that command into lines.

For example, consider the following Jinja2 expression:

{{ query('ansible.builtin.pipe', 'ls files') }}

This expression returns the raw output of the ls command as a string. If you use the lines plug-in, then the expression is as follows:

{{ query('ansible.builtin.lines', 'ls files') }}

This command results in a list with each line of output returned by ls as a list item.

You can use this functionality to retrieve the first line (or any specific line) of output from a set of commands:

- name: Prints the first line of some files
  ansible.builtin.debug:
    msg: "{{ item[0] }}"
  loop:
    - "{{ query('ansible.builtin.lines', 'cat files/my.file') }}"
    - "{{ query('ansible.builtin.lines', 'cat files/my.file.2') }}"

Note that this example might not be the most efficient way to do this particular task, given the existence of the head command.

Similar to the way the file plug-in gets content from a file, the url plug-in gets content from a URL.

{{ lookup('ansible.builtin.url', 'https://my.site.com/my.file') }}

Many options are available for controlling authentication, selecting web proxies, or splitting the returned content into lines.

However, one advantage of using the url plug-in is that you can use the returned data as values in your variables, possibly processing it first with a filter.

The kubernetes.core.k8s plug-in provides full access to the Kubernetes API through the openshift Python module. To fetch a Kubernetes object, you must provide the object type by using the kind option. Providing additional object details, such as the namespace or label_selector option, helps to filter the results:

{{ lookup('kubernetes.core.k8s', kind='Deployment', namespace='ns', resource_name='my_res') }}

Plug-ins are Python scripts. You can develop custom plug-ins and use them in your playbooks. For Ansible to find your lookup plug-ins, copy them into one of the following locations:

The Ansible team recommends using collections to distribute custom plug-ins. Plug-in development is beyond the scope of this course.