Variables, Conditionals, and Loops

Updated Dec 17, 2020 ·

Overview

Variables make playbooks reusable. Conditionals decide whether a task should run. Loops repeat a task for multiple values.

Variables

Variables can be defined in several places.

vars:
  package_name: httpd
  service_name: httpd

Use variables with Jinja2 syntax.

- name: Install package
  ansible.builtin.yum:
    name: "{{ package_name }}"
    state: present

Variable Locations

Location	Purpose
vars	Defines values inside a play.
vars_files	Loads variables from a separate file.
group_vars	Applies variables to an inventory group.
host_vars	Applies variables to one host.
register	Stores task output for later tasks.

Registered Variables

Register command output, then use it later.

- name: Check uptime
  ansible.builtin.command: uptime
  register: uptime_result

- name: Show uptime
  ansible.builtin.debug:
    var: uptime_result.stdout

Conditionals

Use when to run a task only when a condition is true.

- name: Install Apache on Red Hat hosts
  ansible.builtin.yum:
    name: httpd
    state: present
  when: ansible_facts['os_family'] == "RedHat"

Loops

Use loop to repeat a task.

- name: Create users
  ansible.builtin.user:
    name: "{{ item }}"
    state: present
  loop:
    - alice
    - bob
    - carol

Loops with Dictionaries

- name: Create users with groups
  ansible.builtin.user:
    name: "{{ item.name }}"
    groups: "{{ item.groups }}"
    state: present
  loop:
    - name: alice
      groups: wheel
    - name: bob
      groups: developers

Note: Use clear variable names. A readable playbook is easier to troubleshoot than a clever one.