By default Ansible requires values for all variables in a templated expression. However, you can make specific variables optional. For example, you might want to use a system default for some items and control the value for others. To make a variable optional, set the default value to the special variable ``omit``::
By default Ansible requires values for all variables in a templated expression. However, you can make specific variables optional. For example, you might want to use a system default for some items and control the value for others. To make a variable optional, set the default value to the special variable ``omit``::
- name: touch files with an optional mode
- name: Touch files with an optional mode
file:
ansible.builtin.file:
dest: "{{ item.path }}"
dest: "{{ item.path }}"
state: touch
state: touch
mode: "{{ item.mode | default(omit) }}"
mode: "{{ item.mode | default(omit) }}"
@ -55,14 +55,14 @@ By default Ansible requires values for all variables in a templated expression.
In this example, the default mode for the files ``/tmp/foo`` and ``/tmp/bar`` is determined by the umask of the system. Ansible does not send a value for ``mode``. Only the third file, ``/tmp/baz``, receives the `mode=0444` option.
In this example, the default mode for the files ``/tmp/foo`` and ``/tmp/bar`` is determined by the umask of the system. Ansible does not send a value for ``mode``. Only the third file, ``/tmp/baz``, receives the `mode=0444` option.
..note:: If you are "chaining" additional filters after the ``default(omit)`` filter, you should instead do something like this:
..note:: If you are "chaining" additional filters after the ``default(omit)`` filter, you should instead do something like this:
``"{{ foo | default(None) | some_filter or omit }}"``. In this example, the default ``None`` (Python null) value will cause the later filters to fail, which will trigger the ``or omit`` portion of the logic. Using ``omit`` in this manner is very specific to the later filters you're chaining though, so be prepared for some trial and error if you do this.
``"{{ foo | default(None) | some_filter or omit }}"``. In this example, the default ``None`` (Python null) value will cause the later filters to fail, which will trigger the ``or omit`` portion of the logic. Using ``omit`` in this manner is very specific to the later filters you are chaining though, so be prepared for some trial and error if you do this.
.._forcing_variables_to_be_defined:
.._forcing_variables_to_be_defined:
Defining mandatory values
Defining mandatory values
-------------------------
-------------------------
If you configure Ansible to ignore undefined variables, you may want to define some values as mandatory. By default, Ansible fails if a variable in your playbook or command is undefined. You can configure Ansible to allow undefined variables by setting :ref:`DEFAULT_UNDEFINED_VAR_BEHAVIOR` to ``false``. In that case, you may want to require some variables to be defined. You can do with this with::
If you configure Ansible to ignore undefined variables, you may want to define some values as mandatory. By default, Ansible fails if a variable in your playbook or command is undefined. You can configure Ansible to allow undefined variables by setting :ref:`DEFAULT_UNDEFINED_VAR_BEHAVIOR` to ``false``. In that case, you may want to require some variables to be defined. You can do this with::
{{ variable | mandatory }}
{{ variable | mandatory }}
@ -234,10 +234,12 @@ If you are reading in some already formatted data::
Andrew Klychkov
4 years ago
committed by