Loops & conditionals

Two small features do most of the heavy lifting in real playbooks: repeating a task over a list, and skipping a task unless some condition is true.

# loop — install several packages with one task, not five
- name: Install required packages
  apt:
    name: "{{ item }}"
    state: present
  loop:
    - nginx
    - git
    - curl
    - htop

# conditional — only run on Debian-family hosts
- name: Install nginx (Debian/Ubuntu)
  apt:
    name: nginx
    state: present
  when: ansible_facts['os_family'] == "Debian"

- name: Install nginx (RedHat/CentOS)
  yum:
    name: nginx
    state: present
  when: ansible_facts['os_family'] == "RedHat"

Loops and conditionals combine freely — loop over a list of users, but only create the ones flagged as active:

- name: Create active users
  user:
    name: "{{ item.name }}"
    state: present
  loop:
    - { name: alice, active: true }
    - { name: bob,   active: false }
  when: item.active