What if a remote environment variable doesn't exist? Ansible take this as an fatal error. How to avoid that?

Question

I want to do some check using remote environment variables, which can be read from format like this

{{ ansible_env.NGINX_HOME }}

This "path" or environment variable can be absent, and that's the purpose of that check anyway.

But Ansible treat this as a fatal error, showing error message like

One or more undefined variables: 'dict object' has no attribute 'NGINX_HOME'

What can I do to just skip this?

Answer 1

Using a Jinja filter you can specify a default value if the variable is undefined:

{{ ansible_env.NGINX_HOME|default('') }}

This will default the value to an empty string if it doesn't exist.

Another options is if you are using that var in a task you can conditionally run the task only if that var is defined:

- shell: echo {{ ansible_env.NGINX_HOME}}
  when: "'NGINX_HOME' in ansible_env"

Answer 2

You can also set all variables as not mandatory in ansible.cfg.

And set variables as mandatory case by case with {{var | mandatory }}

http://docs.ansible.com/ansible/playbooks_filters.html#forcing-variables-to-be-defined