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.
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>`.
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.
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::
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::
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:
[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
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"}
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``.
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.
