Jinja2 tests
============

.. contents:: Topics


Tests in Jinja2 are a way of evaluating template expressions and returning True or False.
Jinja2 ships with many of these. See `builtin tests`_ in the official Jinja2 template documentation.
Tests are very similar to filters and are used mostly the same way, but they can also be used in list
processing filters, like C(map()) and C(select()) to choose items in the list.

Like filters, tests always execute on the Ansible controller, **not** on the target of a task, as they test local data.

In addition to those Jinja2 tests, Ansible supplies a few more and users can easily create their own.

.. _testing_strings:

Testing strings
---------------

To match strings against a substring or a regex, use the "match" or "search" filter::

    vars:
      url: "http://example.com/users/foo/resources/bar"

    tasks:
        - shell: "msg='matched pattern 1'"
          when: url | match("http://example.com/users/.*/resources/.*")

        - debug: "msg='matched pattern 2'"
          when: url | search("/users/.*/resources/.*")

        - debug: "msg='matched pattern 3'"
          when: url | search("/users/")

'match' requires a complete match in the string, while 'search' only requires matching a subset of the string.


.. _testing_versions:

Version Comparison
------------------

.. versionadded:: 1.6

To compare a version number, such as checking if the ``ansible_distribution_version``
version is greater than or equal to '12.04', you can use the ``version_compare`` filter.

The ``version_compare`` filter can also be used to evaluate the ``ansible_distribution_version``::

    {{ ansible_distribution_version | version_compare('12.04', '>=') }}

If ``ansible_distribution_version`` is greater than or equal to 12, this filter returns True, otherwise False.

The ``version_compare`` filter accepts the following operators::

    <, lt, <=, le, >, gt, >=, ge, ==, =, eq, !=, <>, ne

This test also accepts a 3rd parameter, ``strict`` which defines if strict version parsing should
be used.  The default is ``False``, but this setting as ``True`` uses more strict version parsing::

    {{ sample_version_var | version_compare('1.0', operator='lt', strict=True) }}


.. _math_tests:

Group theory tests
------------------

.. versionadded:: 2.1

To see if a list includes or is included by another list, you can use 'issubset' and 'issuperset'::

    vars:
        a: [1,2,3,4,5]
        b: [2,3]
    tasks:
        - debug: msg="A includes B"
          when: a|issuperset(b)

        - debug: msg="B is included in A"
          when: b|issubset(a)


.. _path_tests:

Testing paths
-------------

The following tests can provide information about a path on the controller::

    - debug: msg="path is a directory"
      when: mypath|is_dir

    - debug: msg="path is a file"
      when: mypath|is_file

    - debug: msg="path is a symlink"
      when: mypath|is_link

    - debug: msg="path already exists"
      when: mypath|exists

    - debug: msg="path is {{ (mypath|is_abs)|ternary('absolute','relative')}}"

    - debug: msg="path is the same file as path2"
      when: mypath|samefile(path2)

    - debug: msg="path is a mount"
      when: mypath|ismount


.. _test_task_results:

Task results
------------

The following tasks are illustrative of the tests meant to check the status of tasks::

    tasks:

      - shell: /usr/bin/foo
        register: result
        ignore_errors: True

      - debug: msg="it failed"
        when: result|failed

      # in most cases you'll want a handler, but if you want to do something right now, this is nice
      - debug: msg="it changed"
        when: result|changed

      - debug: msg="it succeeded in Ansible >= 2.1"
        when: result|succeeded

      - debug: msg="it succeeded"
        when: result|success

      - debug: msg="it was skipped"
        when: result|skipped

.. note:: From 2.1, you can also use success, failure, change, and skip so that the grammar matches, for those who need to be strict about it.



.. _builtin tests: http://jinja.pocoo.org/docs/templates/#builtin-tests

.. seealso::

   :doc:`playbooks`
       An introduction to playbooks
   :doc:`playbooks_conditionals`
       Conditional statements in playbooks
   :doc:`playbooks_variables`
       All about variables
   :doc:`playbooks_loops`
       Looping in playbooks
   :doc:`playbooks_roles`
       Playbook organization by roles
   :doc:`playbooks_best_practices`
       Best practices in playbooks
   `User Mailing List <http://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


