How to exclude an host in Ansible Jinja2 template for-loop?

Question

I have a template named foo.yml.j2 used in an Ansible task to generate a foo.yml file:

      {% for host in ansible_play_hosts_all %}
      {{ host }},
      {% endfor %}

Everything works fine except I need something like the following statement: For every host in ansible_play_hosts_all except for host==bar do this or that.

Is this achievable or the only way to do this is to categorize my hosts in different groups and use ansible_play_hosts_group?

Both answers are great and work like charm, I accepted the longer one since it gives more options and is more well-explained. — Sinux, Sep 14 '22 at 11:14
There is also a `for … if …` construct in Jinja if you don’t have enough option already: https://stackoverflow.com/questions/12655155/jinja2-for-loop-with-conditions — β.εηοιτ.βε, Sep 14 '22 at 11:24

score 2 · Answer 1 · answered Sep 14 '22 at 11:08

2

You can use the reject filter to take your host out of the list so that it is not part of your loop:

{% for host in ansible_play_hosts_all | reject('==', 'bar') %}
{{ host }},
{% endfor %}

answered Sep 14 '22 at 11:08

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Vladimir Botka · Accepted Answer · 2022-09-14T11:10:11.680

There are more options. The trivial one is using the condition in Jinja

{% for host in ansible_play_hosts_all %}
{% if host != 'bar' %}
{{ host }},
{% endif %}
{% endfor %}

Fit the format to your needs.

^{Example of a complete playbook for testing
- hosts: host_1,host_2,host_3
gather_facts: false
tasks:
- debug:
msg: |
{% for host in ansible_play_hosts_all %}
{% if host != 'host_2' %}
{{ host }},
{% endif %}
{% endfor %}
run_once: true

gives (abridged)
msg: |-
host_1,
host_3,}

The next option is to remove blacklisted hosts from the loop, e.g.

blacklist: [host_2]

The template below gives the same result

          {% for host in ansible_play_hosts_all|difference(blacklist) %}
          {{ host }},
          {% endfor %}

Works like a charm, you've helped me before, thank you so much. — Sinux, Sep 14 '22 at 11:14

How to exclude an host in Ansible Jinja2 template for-loop?

2 Answers2