@ -31,17 +31,21 @@ Comparing ``loop`` and ``with_*``
- [2,3]
- 4
you would need::
you would need
loop: "{{ [1, [2,3] ,4] | flatten(1) }}"
..code-block:: yaml+jinja
loop: "{{ [1, [2, 3], 4] | flatten(1) }}"
* Any ``with_*`` statement that requires using ``lookup`` within a loop should not be converted to use the ``loop`` keyword. For example, instead of doing:
Repeated tasks can be written as standard loops over a simple list of strings. You can define the list directly in the task::
Repeated tasks can be written as standard loops over a simple list of strings. You can define the list directly in the task.
..code-block:: yaml+jinja
- name: Add several users
ansible.builtin.user:
@ -64,11 +70,15 @@ Repeated tasks can be written as standard loops over a simple list of strings. Y
- testuser1
- testuser2
You can define the list in a variables file, or in the 'vars' section of your play, then refer to the name of the list in the task::
You can define the list in a variables file, or in the 'vars' section of your play, then refer to the name of the list in the task.
..code-block:: yaml+jinja
loop: "{{ somelist }}"
Either of these examples would be the equivalent of::
Either of these examples would be the equivalent of
..code-block:: yaml
- name: Add user testuser1
ansible.builtin.user:
@ -82,25 +92,29 @@ Either of these examples would be the equivalent of::
state: present
groups: "wheel"
You can pass a list directly to a parameter for some plugins. Most of the packaging modules, like :ref:`yum <yum_module>` and :ref:`apt <apt_module>`, have this capability. When available, passing the list to a parameter is better than looping over the task. For example::
You can pass a list directly to a parameter for some plugins. Most of the packaging modules, like :ref:`yum <yum_module>` and :ref:`apt <apt_module>`, have this capability. When available, passing the list to a parameter is better than looping over the task. For example
..code-block:: yaml+jinja
- name: Optimal yum
ansible.builtin.yum:
name: "{{ list_of_packages }}"
name: "{{ list_of_packages }}"
state: present
- name: Non-optimal yum, slower and may cause issues with interdependencies
ansible.builtin.yum:
name: "{{ item }}"
name: "{{ item }}"
state: present
loop: "{{ list_of_packages }}"
loop: "{{ list_of_packages }}"
Check the :ref:`module documentation <modules_by_category>` to see if you can pass a list to any particular module's parameter(s).
Iterating over a list of hashes
-------------------------------
If you have a list of hashes, you can reference subkeys in a loop. For example::
If you have a list of hashes, you can reference subkeys in a loop. For example:
..code-block:: yaml+jinja
- name: Add several users
ansible.builtin.user:
@ -119,7 +133,7 @@ Iterating over a dictionary
To loop over a dict, use the :ref:`dict2items <dict_filter>`:
..code-block:: yaml
..code-block:: yaml+jinja
- name: Using dict2items
ansible.builtin.debug:
@ -135,7 +149,9 @@ Here, we are iterating over `tag_data` and printing the key and the value from i
Registering variables with a loop
=================================
You can register the output of a loop as a variable. For example::
You can register the output of a loop as a variable. For example
..code-block:: yaml+jinja
- name: Register loop output as a variable
ansible.builtin.shell: "echo {{ item }}"
@ -144,7 +160,9 @@ You can register the output of a loop as a variable. For example::
- "two"
register: echo
When you use ``register`` with a loop, the data structure placed in the variable will contain a ``results`` attribute that is a list of all responses from the module. This differs from the data structure returned when using ``register`` without a loop::
When you use ``register`` with a loop, the data structure placed in the variable will contain a ``results`` attribute that is a list of all responses from the module. This differs from the data structure returned when using ``register`` without a loop.
..code-block:: json
{
"changed": true,
@ -183,7 +201,9 @@ When you use ``register`` with a loop, the data structure placed in the variable
]
}
Subsequent loops over the registered variable to inspect the results may look like::
Subsequent loops over the registered variable to inspect the results may look like
..code-block:: yaml+jinja
- name: Fail if return code is not 0
ansible.builtin.fail:
@ -191,7 +211,9 @@ Subsequent loops over the registered variable to inspect the results may look li
when: item.rc != 0
loop: "{{ echo.results }}"
During iteration, the result of the current item will be placed in the variable::
During iteration, the result of the current item will be placed in the variable.
..code-block:: yaml+jinja
- name: Place the result of the current item in the variable
ansible.builtin.shell: echo "{{ item }}"
@ -209,7 +231,9 @@ Complex loops
Iterating over nested lists
---------------------------
You can use Jinja2 expressions to iterate over complex lists. For example, a loop can combine nested lists::
You can use Jinja2 expressions to iterate over complex lists. For example, a loop can combine nested lists.
..code-block:: yaml+jinja
- name: Give users access to multiple databases
community.mysql.mysql_user:
@ -217,7 +241,7 @@ You can use Jinja2 expressions to iterate over complex lists. For example, a loo
@ -227,7 +251,9 @@ Retrying a task until a condition is met
..versionadded:: 1.4
You can use the ``until`` keyword to retry a task until a certain condition is met. Here's an example::
You can use the ``until`` keyword to retry a task until a certain condition is met. Here's an example:
..code-block:: yaml
- name: Retry a task until a certain condition is met
ansible.builtin.shell: /usr/bin/foo
@ -247,7 +273,9 @@ When you run a task with ``until`` and register the result as a variable, the re
Looping over inventory
----------------------
To loop over your inventory, or just a subset of it, you can use a regular ``loop`` with the ``ansible_play_batch`` or ``groups`` variables::
To loop over your inventory, or just a subset of it, you can use a regular ``loop`` with the ``ansible_play_batch`` or ``groups`` variables.
..code-block:: yaml+jinja
- name: Show all the hosts in the inventory
ansible.builtin.debug:
@ -259,7 +287,9 @@ To loop over your inventory, or just a subset of it, you can use a regular ``loo
msg: "{{ item }}"
loop: "{{ ansible_play_batch }}"
There is also a specific lookup plugin ``inventory_hostnames`` that can be used like this::
There is also a specific lookup plugin ``inventory_hostnames`` that can be used like this
..code-block:: yaml+jinja
- name: Show all the hosts in the inventory
ansible.builtin.debug:
@ -282,7 +312,9 @@ The ``loop`` keyword requires a list as input, but the ``lookup`` keyword return
You can force ``lookup`` to return a list to ``loop`` by using ``wantlist=True``, or you can use ``query`` instead.
These examples do the same thing::
The following two examples do the same thing.
..code-block:: yaml+jinja
loop: "{{ query('inventory_hostnames', 'all') }}"
@ -301,7 +333,9 @@ Limiting loop output with ``label``
-----------------------------------
..versionadded:: 2.2
When looping over complex data structures, the console output of your task can be enormous. To limit the displayed output, use the ``label`` directive with ``loop_control``::
When looping over complex data structures, the console output of your task can be enormous. To limit the displayed output, use the ``label`` directive with ``loop_control``.
..code-block:: yaml+jinja
- name: Create servers
digital_ocean:
@ -326,7 +360,9 @@ Pausing within a loop
---------------------
..versionadded:: 2.2
To control the time (in seconds) between the execution of each item in a task loop, use the ``pause`` directive with ``loop_control``::
To control the time (in seconds) between the execution of each item in a task loop, use the ``pause`` directive with ``loop_control``.
..code-block:: yaml+jinja
# main.yml
- name: Create servers, pause 3s before creating next
@ -343,7 +379,9 @@ Tracking progress through a loop with ``index_var``
To keep track of where you are in a loop, use the ``index_var`` directive with ``loop_control``. This directive specifies a variable name to contain the current loop index::
To keep track of where you are in a loop, use the ``index_var`` directive with ``loop_control``. This directive specifies a variable name to contain the current loop index.
..code-block:: yaml+jinja
- name: Count our fruit
ansible.builtin.debug:
@ -362,7 +400,9 @@ Defining inner and outer variable names with ``loop_var``
..versionadded:: 2.1
You can nest two looping tasks using ``include_tasks``. However, by default Ansible sets the loop variable ``item`` for each loop. This means the inner, nested loop will overwrite the value of ``item`` from the outer loop.
You can specify the name of the variable for each loop using ``loop_var`` with ``loop_control``::
You can specify the name of the variable for each loop using ``loop_var`` with ``loop_control``.
..code-block:: yaml+jinja
# main.yml
- include_tasks: inner.yml
@ -418,7 +458,9 @@ Accessing the name of your loop_var
As of Ansible 2.8 you can get the name of the value provided to ``loop_control.loop_var`` using the ``ansible_loop_var`` variable
For role authors, writing roles that allow loops, instead of dictating the required ``loop_var`` value, you can gather the value via::
For role authors, writing roles that allow loops, instead of dictating the required ``loop_var`` value, you can gather the value via the following
Matěj G
3 years ago
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