# template substitution

**URL:** <https://forum.ansible.com/t/template-substitution/21623>\
**Category:** Ansible Project\
**Created:** [June 1, 2016, 5:23am UTC](https://forum.ansible.com/t/template-substitution/21623 "2016-06-01T05:23:10Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![Peter\_Gray](https://avatars.discourse-cdn.com/v4/letter/p/ebca7d/32.png) [@Peter\_Gray](https://forum.ansible.com/u/Peter_Gray)\
**Post date:** [June 1, 2016, 5:23am UTC](https://forum.ansible.com/t/template-substitution/21623/1 "2016-06-01T05:23:10Z")

</div>

If I have in a template file

---

<div class="post-metadata">

**Author:** ![Johannes\_Kastl](https://avatars.discourse-cdn.com/v4/letter/j/bbe5ce/32.png) [@Johannes\_Kastl](https://forum.ansible.com/u/Johannes_Kastl)\
**Post date:** [June 1, 2016, 1:01pm UTC](https://forum.ansible.com/t/template-substitution/21623/2 "2016-06-01T13:01:23Z")

</div>

I normally write it like this:

{% if i\_want\_yes %}  
# yes  
{% else %}  
# no  
{% endif %}

Would that work for you?

Johannes

---

<div class="post-metadata">

**Author:** ![Brian\_Coca](https://avatars.discourse-cdn.com/v4/letter/b/6de8d8/32.png) [@Brian\_Coca](https://forum.ansible.com/u/Brian_Coca)\
**Post date:** [June 1, 2016, 1:12pm UTC](https://forum.ansible.com/t/template-substitution/21623/3 "2016-06-01T13:12:52Z")

</div>

ansible uses the trim\_blocks setting when invoking jinja, by default its ‘yes’.

ansible allows for overrides by creating a special header:

```auto
#jinja2: trim_blocks: False
#
# {% if i_want_yes %} yes {% else %} no {% endif %}
#

```

---

<div class="post-metadata">

**Author:** ![Peter\_Gray](https://avatars.discourse-cdn.com/v4/letter/p/ebca7d/32.png) [@Peter\_Gray](https://forum.ansible.com/u/Peter_Gray)\
**Post date:** [June 1, 2016, 10:46pm UTC](https://forum.ansible.com/t/template-substitution/21623/4 "2016-06-01T22:46:40Z")

</div>

Many thanks for this information. For future reference where is this documented?

The interaction of ansible with jinga2 seems a bit opaque.

---

<div class="post-metadata">

**Author:** ![Josh\_Smift1](https://avatars.discourse-cdn.com/v4/letter/j/bcef8e/32.png) [@Josh\_Smift1](https://forum.ansible.com/u/Josh_Smift1)\
**Post date:** [June 2, 2016, 4:01am UTC](https://forum.ansible.com/t/template-substitution/21623/5 "2016-06-02T04:01:28Z")

</div>

> Many thanks for this information. For future reference where is this  
> documented?

[https://groups.google.com/forum/#!topic/ansible-project/qHyIjyal\_Ic](https://groups.google.com/forum/#!topic/ansible-project/qHyIjyal_Ic) is a  
thread where it came up before, which says

&nbsp;&nbsp;you can use a per template header to override this, you can see an  
&nbsp;&nbsp;example in the template docs.

&nbsp;&nbsp;[https://docs.ansible.com/template\_module.html](https://docs.ansible.com/template_module.html)

which is now at [http://docs.ansible.com/ansible/template\_module.html](http://docs.ansible.com/ansible/template_module.html), and  
which only seems to mention it in a note saying

&nbsp;&nbsp;Since Ansible version 0.9, templates are loaded with trim\_blocks=True.

and not any actual examples, or any explanation of what trim\_blocks does,  
so it could be hard to spot this if you didn't already know what you were  
looking for.

> The interaction of ansible with jinga2 seems a bit opaque.

That page also doesn't mention  
[http://docs.ansible.com/ansible/playbooks\_filters.html](http://docs.ansible.com/ansible/playbooks_filters.html), which I've found  
to be super useful in turning up examples of Ansible-specific Jinja filters.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;-Josh (jbs@care.com)

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