Docs: Add code-blocks to user_guide/intro_patterns.rst (#75941)

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@ -11,11 +11,15 @@ When you execute Ansible through an ad hoc command or by running a playbook, you
Using patterns
--------------
You use a pattern almost any time you execute an ad hoc command or a playbook. The pattern is the only element of an :ref:`ad hoc command<intro_adhoc>` that has no flag. It is usually the second element::
You use a pattern almost any time you execute an ad hoc command or a playbook. The pattern is the only element of an :ref:`ad hoc command<intro_adhoc>` that has no flag. It is usually the second element:
.. code-block:: bash
ansible <pattern> -m <module_name> -a "<module options>"
For example::
For example:
.. code-block:: bash
ansible webservers -m service -a "name=httpd state=restarted"
@ -26,7 +30,9 @@ In a playbook the pattern is the content of the ``hosts:`` line for each play:
- name: <play_name>
hosts: <pattern>
For example::
For example:
.. code-block:: yaml
- name: restart webservers
hosts: webservers
@ -63,20 +69,26 @@ This table lists common patterns for targeting inventory hosts and groups.
.. note:: You can use either a comma (``,``) or a colon (``:``) to separate a list of hosts. The comma is preferred when dealing with ranges and IPv6 addresses.
Once you know the basic patterns, you can combine them. This example::
Once you know the basic patterns, you can combine them. This example:
.. code-block:: yaml
webservers:dbservers:&staging:!phoenix
targets all machines in the groups 'webservers' and 'dbservers' that are also in
the group 'staging', except any machines in the group 'phoenix'.
You can use wildcard patterns with FQDNs or IP addresses, as long as the hosts are named in your inventory by FQDN or IP address::
You can use wildcard patterns with FQDNs or IP addresses, as long as the hosts are named in your inventory by FQDN or IP address:
.. code-block:: yaml
192.0.\*
\*.example.com
\*.com
You can mix wildcard patterns and groups at the same time::
You can mix wildcard patterns and groups at the same time:
.. code-block:: yaml
one*.com:dbservers
@ -100,7 +112,9 @@ Your pattern must match your inventory syntax. If you define a host as an :ref:`
maxRequestsPerChild: 808
host: 127.0.0.2
you must use the alias in your pattern. In the example above, you must use ``host1`` in your pattern. If you use the IP address, you will once again get the error::
you must use the alias in your pattern. In the example above, you must use ``host1`` in your pattern. If you use the IP address, you will once again get the error:
.. code-block:: console
[WARNING]: Could not match supplied host pattern, ignoring: 127.0.0.2
@ -112,21 +126,27 @@ The common patterns described above will meet most of your needs, but Ansible of
Using variables in patterns
^^^^^^^^^^^^^^^^^^^^^^^^^^^
You can use variables to enable passing group specifiers via the ``-e`` argument to ansible-playbook::
You can use variables to enable passing group specifiers via the ``-e`` argument to ansible-playbook:
.. code-block:: bash
webservers:!{{ excluded }}:&{{ required }}
Using group position in patterns
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
You can define a host or subset of hosts by its position in a group. For example, given the following group::
You can define a host or subset of hosts by its position in a group. For example, given the following group:
.. code-block:: ini
[webservers]
cobweb
webbing
weber
you can use subscripts to select individual hosts or ranges within the webservers group::
you can use subscripts to select individual hosts or ranges within the webservers group:
.. code-block:: yaml
webservers[0] # == cobweb
webservers[-1] # == weber
@ -138,7 +158,9 @@ you can use subscripts to select individual hosts or ranges within the webserver
Using regexes in patterns
^^^^^^^^^^^^^^^^^^^^^^^^^
You can specify a pattern as a regular expression by starting the pattern with ``~``::
You can specify a pattern as a regular expression by starting the pattern with ``~``:
.. code-block:: yaml
~(web|db).*\.example\.com
@ -175,11 +197,15 @@ You can also limit the hosts you target on a particular run with the ``--limit``
Patterns and ansible-playbook flags
-----------------------------------
You can change the behavior of the patterns defined in playbooks using command-line options. For example, you can run a playbook that defines ``hosts: all`` on a single host by specifying ``-i 127.0.0.2,`` (note the trailing comma). This works even if the host you target is not defined in your inventory. You can also limit the hosts you target on a particular run with the ``--limit`` flag::
You can change the behavior of the patterns defined in playbooks using command-line options. For example, you can run a playbook that defines ``hosts: all`` on a single host by specifying ``-i 127.0.0.2,`` (note the trailing comma). This works even if the host you target is not defined in your inventory. You can also limit the hosts you target on a particular run with the ``--limit`` flag:
.. code-block:: bash
ansible-playbook site.yml --limit datacenter2
Finally, you can use ``--limit`` to read the list of hosts from a file by prefixing the file name with ``@``::
Finally, you can use ``--limit`` to read the list of hosts from a file by prefixing the file name with ``@``:
.. code-block:: bash
ansible-playbook site.yml --limit @retry_hosts.txt

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