.. _lookup_plugins:

Lookup Plugins
==============

.. contents::
   :local:
   :depth: 2

Lookup plugins are an Ansible-specific extension to the Jinja2 templating language. You can use lookup plugins to access data from outside sources (files, databases, key/value stores, APIs, and other services) within your playbooks. Like all :ref:`templating <playbooks_templating>`, lookups execute and are evaluated on the Ansible control machine. Ansible makes the data returned by a lookup plugin available using the standard templating system. You can use lookup plugins to load variables or templates with information from external sources.

.. note::
   - Lookups are executed with a working directory relative to the role or play,
     as opposed to local tasks, which are executed relative the executed script.
   - Pass ``wantlist=True`` to lookups to use in Jinja2 template "for" loops.

.. warning::
   - Some lookups pass arguments to a shell. When using variables from a remote/untrusted source, use the `|quote` filter to ensure safe usage.


.. _enabling_lookup:

Enabling lookup plugins
-----------------------

Ansible enables all lookup plugins it can find. You can activate a custom lookup by either dropping it into a ``lookup_plugins`` directory adjacent to your play, inside the ``plugins/lookup/`` directory of a collection you have installed, inside a standalone role, or in one of the lookup directory sources configured in :ref:`ansible.cfg <ansible_configuration_settings>`.


.. _using_lookup:

Using lookup plugins
--------------------

You can use lookup plugins anywhere you can use templating in Ansible: in a play, in variables file, or in a Jinja2 template for the :ref:`template <template_module>` module.

.. code-block:: YAML+Jinja

  vars:
    file_contents: "{{lookup('file', 'path/to/file.txt')}}"

Lookups are an integral part of loops. Wherever you see ``with_``, the part after the underscore is the name of a lookup. For this reason, most lookups output lists and take lists as input; for example, ``with_items`` uses the :ref:`items <items_lookup>` lookup::

  tasks:
    - name: count to 3
      debug: msg={{item}}
      with_items: [1, 2, 3]

You can combine lookups with :ref:`filters <playbooks_filters>`, :ref:`tests <playbooks_tests>` and even each other to do some complex data generation and manipulation. For example::

  tasks:
    - name: valid but useless and over complicated chained lookups and filters
      debug: msg="find the answer here:\n{{ lookup('url', 'https://google.com/search/?q=' + item|urlencode)|join(' ') }}"
      with_nested:
        - "{{lookup('consul_kv', 'bcs/' + lookup('file', '/the/question') + ', host=localhost, port=2000')|shuffle}}"
        - "{{lookup('sequence', 'end=42 start=2 step=2')|map('log', 4)|list)}}"
        - ['a', 'c', 'd', 'c']

.. versionadded:: 2.6

You can control how errors behave in all lookup plugins by setting ``errors`` to ``ignore``, ``warn``, or ``strict``. The default setting is ``strict``, which causes the task to fail if the lookup returns an error. For example:

To ignore lookup errors::

    - name: if this file does not exist, I do not care .. file plugin itself warns anyway ...
      debug: msg="{{ lookup('file', '/nosuchfile', errors='ignore') }}"

.. code-block:: ansible-output

    [WARNING]: Unable to find '/nosuchfile' in expected paths (use -vvvvv to see paths)

    ok: [localhost] => {
        "msg": ""
    }


To get a warning instead of a failure::

    - name: if this file does not exist, let me know, but continue
      debug: msg="{{ lookup('file', '/nosuchfile', errors='warn') }}"

.. code-block:: ansible-output

    [WARNING]: Unable to find '/nosuchfile' in expected paths (use -vvvvv to see paths)

    [WARNING]: An unhandled exception occurred while running the lookup plugin 'file'. Error was a <class 'ansible.errors.AnsibleError'>, original message: could not locate file in lookup: /nosuchfile

    ok: [localhost] => {
        "msg": ""
    }


To get a fatal error (the default)::

    - name: if this file does not exist, FAIL (this is the default)
      debug: msg="{{ lookup('file', '/nosuchfile', errors='strict') }}"

.. code-block:: ansible-output

    [WARNING]: Unable to find '/nosuchfile' in expected paths (use -vvvvv to see paths)

    fatal: [localhost]: FAILED! => {"msg": "An unhandled exception occurred while running the lookup plugin 'file'. Error was a <class 'ansible.errors.AnsibleError'>, original message: could not locate file in lookup: /nosuchfile"}


.. _query:

Forcing lookups to return lists: ``query`` and ``wantlist=True``
----------------------------------------------------------------

.. versionadded:: 2.5

In Ansible 2.5, a new Jinja2 function called ``query`` was added for invoking lookup plugins. The difference between ``lookup`` and ``query`` is largely that ``query`` will always return a list.
The default behavior of ``lookup`` is to return a string of comma separated values. ``lookup`` can be explicitly configured to return a list using ``wantlist=True``.

This feature provides an easier and more consistent interface for interacting with the new ``loop`` keyword, while maintaining backwards compatibility with other uses of ``lookup``.

The following examples are equivalent:

.. code-block:: jinja

    lookup('dict', dict_variable, wantlist=True)

    query('dict', dict_variable)

As demonstrated above, the behavior of ``wantlist=True`` is implicit when using ``query``.

Additionally, ``q`` was introduced as a shortform of ``query``:

.. code-block:: jinja

    q('dict', dict_variable)


.. _lookup_plugins_list:

Plugin list
-----------

You can use ``ansible-doc -t lookup -l`` to see the list of available plugins. Use ``ansible-doc -t lookup <plugin name>`` to see specific documents and examples.


.. seealso::

   :ref:`about_playbooks`
       An introduction to playbooks
   :ref:`inventory_plugins`
       Ansible inventory plugins
   :ref:`callback_plugins`
       Ansible callback plugins
   :ref:`playbooks_filters`
       Jinja2 filter plugins
   :ref:`playbooks_tests`
       Jinja2 test plugins
   :ref:`playbooks_lookups`
       Jinja2 lookup plugins
   `User Mailing List <https://groups.google.com/group/ansible-devel>`_
       Have a question?  Stop by the google group!
   `irc.freenode.net <http://irc.freenode.net>`_
       #ansible IRC chat channel
