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Chapter 6

Variables

Variables can be set in couple ways. Can be stored in vars files, can be set in playbooks, overrided in command line in ansible-playbook command, or set (or generated) through tasks.

syntax

The base syntax is straightforward:

variable: "string"
variable: number
variable: boolean

Dictonaries

Defining the dictionary:

var_dict:
  field1: "string"
  field2: "string"
  field3: number

To access the value, use:

var_dict.field2

or

var_dict['field2']

It is possible to create a more compicated dictionary:

var_dict:
  me:
    name: "John"
    age: 40
  you:
    name: "Mike"
    age: 65

Access to this variable is simple:

- name: Print phone records
  debug:
    msg: "{{ item.value.name }} is {{ item.value.age }}, and the name in the dictionary is {{ item.key }}"
  loop: "{{ lookup('dict', users) }}"

This code will print all records from dictionary.

Defining variables in playbook

Variables have to be declared with some values. If not registered in tasks, have to be set, or imported.
Set variables in playbook:

vars:
  - var1: "value"
  - var2: "value"

Import var files:

vars_file:
  - "path/to/file/vars.yml"

Ansible facts

Very good example of dictionary is Ansible facts. You can take them in the task:

- debug: info=ansible_facts

or:

- debug:
  info: ansible_facts

Method debug is responsible for printing data during execution.

You can access the specific fact directly as a variable:

{{ ansible_facts['devices']['xvda']['model'] }}

This example from documentation will store model of the device xvda.

Register variable

Registering variables gives you more flexibility to use new variable. In this way you can use registered variable later in the playbook.

For example, you can register as variable the refference to HEAD in github repo. Why? For deployments, for example.

- name: Get HEAD from branch
  command: git ls-remote --heads URL_to_repo | grep 'refs/heads/master'
  register: last_commit

Now, you can use this refference later.

Set your fact

Ansible offers module called set_fact. The most useful feature of it is to set facts-like variable, specific for each host where playbook is run.

Example:

- name: Register fact
  set_fact:
    first_fact: "value"
    other_fact: "other value"

set_fact can be used with register. For example, when you register a variable (like in our example with repo HEAD), Ansible will write a lot of unrelevant (in this case) information, but you wish to have only the hash of the latest state, and then you can send an information contains this hash to Slack, email, or so.

- name: Get HEAD from branch
  command: git ls-remote --heads URL_to_repo | grep 'refs/heads/master'
  register: last_commit

- name: Set hash from branch
  set_fact:
    last_commit_hash="{{last_commit.stdout_lines[0][0:7]}}"

Setting variables in command line

If you wish to override some variable, you can do it during ansible-playbook execution. This has the highest priority.

ansible-playbook provision.yml -e my_var="something"

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