Ansible - Use default if a variable is not defined

Question

I m customizing linux users creation inside my role  I need to let users of my role customize home directory  group name  name  password    I was wondering if there s a more flexible way to cope with default values    I know that the code below is possible   - name  Create default   user      name   default name    when  my variable is not defined   - name  Create custom   user      name     my variable      when  my variable is defined   But as I mentioned  there s a lot of optional variables and this creates a lot of possibilities   Is there something like the code above   user    name   default name      my variable      The code should set name  default name  when my variable isn t defined   I could set all variables on defaults main yml and create the user like that   - name  Create user   user      name     my variable      But those variables are inside a really big hash and there are some hashes inside that hash that can t be a default

User · Answer

If you have a single play that you want to loop over the items, define that list in group_vars/all or somewhere else that makes sense:

all_items:
  - first
  - second
  - third
  - fourth

Then your task can look like this:

  - name: List items or default list
    debug:
      var: item
    with_items: "{{ varlist | default(all_items) }}"

Pass in varlist as a JSON array:

ansible-playbook <playbook_name> --extra-vars='{"varlist": [first,third]}'

Prior to that, you might also want a task that checks that each item in varlist is also in all_items:

  - name: Ensure passed variables are in all_items
    fail:
      msg: "{{ item }} not  in all_items list"
    when: item not in all_items
    with_items: "{{ varlist | default(all_items) }}"

User · Answer

If you are assigning default value for boolean fact then ensure that no quotes is used inside default     - name  create bool default   set fact      name      my bool   default true        For other variables used the same method given in verified answer    - name  Create user   user      name      my variable   default  default value

User · Answer

You can use Jinja s default   - name  Create user   user      name      my variable   default  default value

User · Answer

The question is quite old  but what about   - hosts   localhost    tasks      - debug          msg        a   default      get  nested       get  var   bar         It looks less cumbersome to me

User · Answer

In case you using lookup to set default read from environment you have also set the second parameter of default to true   - set facts      ansible ssh user      lookup  env    SSH USER     default  foo   true        You can also concatenate multiple default definitions   - set facts      ansible ssh user      some var split  -   1    default lookup  env   USER    true    default  foo

User · Answer

If anybody is looking for an option which handles nested variables  there are several such options in this github issue   In short  you need to use  default  filter for every level of nested vars  For a variable  a nested var  it would look like   - hosts   localhost    tasks      - debug          msg        a   default      nested   default       var   default  bar         or you could set default values of empty dicts for each level of vars  maybe using  combine  filter  Or use  json query  filter  But the option I chose seems simpler to me if you have only one level of nesting

User · Answer

Not totally related  but you can also check for both undefined AND empty  for e g my variable   variable   NOTE  only works with ansible version   1 9  see  link   - name  Create user   user      name        my variable    None    ternary  default value   my variable         if my variable is defined else  default value

[ansible] Ansible - Use default if a variable is not defined

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