I am unable to source from Ansible documents a clear meaning of a conditional such as when: var | d(). Is someone able give a clear explanation?
E.g. Below works whether inputing extra-var value from cli or defaulting to local ENV variable value:
vars:
my_var: "{{ e_var | default(ansible_env.USER | default(False,true)) }}"
tasks:
- name: Conditional check
debug:
msg: "{{ my_var }}"
when: my_var | d()
But this fails:
vars:
my_var: "{{ e_var | default(ansible_env.USER | default(false,true)) }}"
tasks:
- name: Conditional check
debug:
msg: "{{ my_var }}"
when: my_var
What is when: my_var | d() exactly doing? How how does it interplay with the | default(false,true) part in the variable declaration?
d is an alias to the default filter. It is a Jinja2 filter, so head for the Jinja2 docs. They work the same:
default(value, default_value=u'', boolean=False)
[ ]
Aliases: d
Regarding the problem you are facing, it is because Ansible processes a condition consisting of only a variable name differently from a more complex expression (which is passed directly to Jinja2/Python) (the actual code starts here):
If the my_var variable has a value of user01, the conditional will try to find a value of user01 variable and fail because it doesn't exist.
If you just add a logical conjunction (which in common sense is redundant), Ansible will process the whole expression differently and it will work:
when: my_var and true
In your case using another default filter in the expression is also redundant, but it prevents Ansible from trying to resolve a "nested" variable value.
Related
I have an Ansible playbook that populates some variables, here is a snippet:
#myTest playbook
---
- hosts: localhost
connection: local
become: False
vars:
- APP_NAME: "{{lookup( 'env', 'name')| mandatory }}"
I'd like to use another lookup first, and take that value if its been populated. Is this achievable in one line? I'm figuring something like Javascript's ||:
- APP_NAME: "{{lookup( 'env', 'customName') || lookup( 'env', 'name')| mandatory }}"
You can use the default filter with an option to trigger it if the value of the preceding expression is an empty string (as in the case of an undefined environment variable):
- APP_NAME: "{{ lookup('env', 'customName') | default(lookup('env', 'name'), true) | mandatory }}"
So I have an Ansible playbook that looks like
---
- hosts: mygroup
tasks:
- debug:
msg: "{{ foo | default(inventory_hostname) }}"
My inventory file looks like
[mygroup]
127.0.0.1
Since foo is not defined anywhere, the debug prints 127.0.0.1 as expected.
But suppose my inventory file looks like
[mygroup]
127.0.0.1 foo=null
When I run the playbook, it prints out the string null. I also tried with foo=None and it prints an empty string. How can set the variable to null through inventory or extra-vars?
This may be useful when I want to unset a variable already defined in a playbook.
I am using Ansible version 2.1.1.0.
Python (hence Ansible) differentiates between an undefined variable and a variable with the none value.
There is no way to "undefine" a variable once it has been defined.
In result even if you set the value to none, the condition you specified will never consider the variable as undefined.
You get a "" in the output log because this is how debug module displays the none-value, not because it's an empty string.
Solution 1
Use a ternary operator with the condition to check for the actual value of foo variable:
- debug:
msg: "{{ ((foo is defined) and (foo != None)) | ternary(foo, inventory_hostname) }}"
Solution 2
Use a "wrapper" dictionary:
Define a default value for the variable inside a "wrapper" dictionary:
foodict:
foo: bar
In the play refer the variable as foodict.foo:
---
- hosts: mygroup
tasks:
- debug:
msg: "{{ foodict.foo | default(inventory_hostname) }}"
Override the value in the inventory file by nullifying the "wrapper" dictionary:
[mygroup]
127.0.0.1 foodict=None
I've got a role that bootstraps a user's OSX workstation. In it, I need to ensure that xdg variables are set properly, using the following precedence:
defaults/main.yml
user's environment variable
any other value (set in vars, host_vars, command line, etc)
I've tried a couple different approaches, but the basic problem I'm having is that I can't nest variable interpolation, so approach one (and all the others I could think of to try) in defaults/main.yml have failed:
# if the env var doesn't exist, it'll set it to an empty string, doesn't look
# like there is a way to specify the 'default' string that should be used
# xdg_cache_home: "{{ lookup('env','XDG_CACHE_HOME') }}"
# this is just bad syntax, can't have nested '{{ }}'
# xdg_config_home: "{{ lookup('env','XDG_CACHE_HOME') | default("{{ home }}/.cache", true) }}"
# this simply fails to define the variable, i'm not sure why
# xdg_cache_home: "{{ default( lookup('env','XDG_CACHE_HOME'), join(lookup('env', 'HOME', '.cache'))) }}"
The next approach I tried was to just set the defaults using the first method (empty string if empty) and then inspect and set a default value in the roles/myrole/tasks/main.yml:
- name: set default xdg_cache_home
set_fact: xdg_cache_home="{{ join(lookup('env', 'HOME', '/.cache')) }}"
when: "{{ xdg_cache_home }}" == ""
But I can't get that to work either. Any suggestions or advice?
Found the answer in the jinja documentation - using the jinja string concatenation operator (~):
xdg_cache_home: "{{ lookup('env', 'XDG_CACHE_HOME') | default(ansible_user_dir ~ '/.cache', true) }}"
xdg_config_home: "{{ lookup('env', 'XDG_CONFIG_HOME') | default(ansible_user_dir ~ '/.config', true) }}"
xdg_data_home: "{{ lookup('env', 'XDG_DATA_HOME') | default(ansible_user_dir ~ '/.local/share', true) }}"
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.
You can use Jinja's default:
- name: Create user
user:
name: "{{ my_variable | default('default_value') }}"
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' }}"
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.
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') }}"
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') }}"
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) }}"
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...
#Roman Kruglov mentioned json_query. It's perfect for nested queries.
An example of json_query sample playbook for existing and non-existing value:
- hosts: localhost
gather_facts: False
vars:
level1:
level2:
level3:
level4: "LEVEL4"
tasks:
- name: Print on existing level4
debug:
var: level1 | json_query('level2.level3.level4') # prints 'LEVEL4'
when: level1 | json_query('level2.level3.level4')
- name: Skip on inexistent level5
debug:
var: level1 | json_query('level2.level3.level4.level5') # skipped
when: level1 | json_query('level2.level3.level4.level5')
You can also use an if statement:
# Firewall manager: firewalld or ufw
firewall: "{{ 'firewalld' if ansible_os_family == 'RedHat' else 'ufw' }}"
I want to conditionally define a variable in an Ansible playbook like this:
my_var: "{{ 'foo' if my_condition}}"
I would like the variable to remain undefined if the condition does not resolve to true.
Ansible gives the following error if I try to execute the code:
fatal: [foo.local] => {'msg': 'AnsibleUndefinedVariable: One or more undefined
variables: the inline if-expression on line 1 evaluated
to false and no else section was defined.', 'failed': True}
Why is this an error anyway?
The complete case looks like this:
{role: foo, my_var: "foo"}
If my_var is defined, the role does something special. In some cases, I don't want the role to do this. I could use when: condition, but then I would have to copy the whole role block. I could also use an extra bool variable, but I would like a solution without having to change the "interface" to the role.
Any ideas?
You could use something like this:
my_var: "{{ 'foo' if my_condition else '' }}"
The 'else' will happen if condition not match, and in this case will set a empty value for the variable. I think this is a short, readable and elegant solution.
This code may help you to define a variable with condition.
- hosts: node1
gather_facts: yes
tasks:
- name: Check File
shell: ls -ld /etc/postfix/post-install
register: result
ignore_errors: yes
- name: Define Variable
set_fact:
exists: "{{ result.stdout }}"
when: result|success
- name: Display Variable
debug: msg="{{ exists }}"
ignore_errors: yes
So here the exists will display only if the condition is true.
My example, after https://stackoverflow.com/a/43403229/5025060:
vars:
sudoGroup: "{{ 'sudo' if ansible_distribution == 'Ubuntu' else 'wheel' }}"
Because of the different sudo conventions used by Ubuntu versus other platforms, here I am telling Ansible to set a variable named sudoGroup to sudo if the platform is Ubuntu, otherwise set it to wheel.
Later in my playbook, I combine the variable with Ansible's user module to add either sudo or wheel to an account's secondary groups depending on the OS Ansible is running on:
- name: Add or update bob account
user:
name: bob
uid: 3205
groups: "{{ sudoGroup }}"
append: yes
NOTES:
Double quotes around the {{ variable }} are required in the user: groups: definition above.
Once I define sudoGroup as above in my playbook's global vars: section, Ansible configures it at run time (based on ansible_distribution) for each target I define in my hosts: section.
I believe you're after the default(omit) filter. (Reference).
As per the example, mode will behave like it wasn't set at all for the first two items in the loop.
- name: touch files with an optional mode
file:
dest: "{{item.path}}"
state: touch
mode: "{{item.mode|default(omit)}}"
loop:
- path: /tmp/foo
- path: /tmp/bar
- path: /tmp/baz
mode: "0444"
This can be set as with bool:
- name: Conditional (true and false)
set_fact:
my_boolean_set_to_be: "{{ 'true' if my_var == 'foo' else 'false' }}"
- name: Display Variable
debug: msg="{{ my_boolean_set_to_be }}"
This can be set as for more conditionals like 'if-ifelse-else' statements:
- name: Conditional for 'my_var' (2 options and one default)
set_fact:
my_var_set_to_be: "{{ 'breakfast' if my_var == 'morning' else 'lunch' if my_var == 'afternoon' else 'dinner' }}"
- name: Display Variable
debug: msg="{{ my_var_set_to_be }}"