Loops and Conditionals in Ansible¶

• In this section, we will cover Loops and Conditionals in Ansible.
• Loops assist in efficiently performing repetitive tasks.
• Conditions allow tasks to be executed based on specific criteria.
• See documentation about Loops and Conditionals in Ansible.
• 

What will we learn?¶

• How to use loop to iterate over lists and dictionaries
• How to use nested loops
• How to use the when clause for conditional task execution
• How to combine loops and conditionals

Prerequisites¶

• Complete the previous lab in order to have Ansible set up.

01. Ansible Loops¶

Basic loop¶

• Ansible provides a loop keyword to execute tasks multiple times with different inputs:

---
- hosts: localhost
  tasks:
    - name: Install multiple packages
      apt:
        name: "{{ item }}"
        state: present
      loop:
        - git
        - curl
        - vim

Loop with dictionaries¶

• Loops can be used with dictionaries to process structured data:

---
- hosts: localhost
  tasks:
    - name: Add multiple users
      user:
        name: "{{ item.name }}"
        shell: "{{ item.shell }}"
      loop:
        - { name: "alice", shell: "/bin/bash" }
        - { name: "bob", shell: "/bin/zsh" }

Nested loops¶

• Nested loops allow iterating over multiple lists:

---
- hosts: localhost
  tasks:
    - name: Assign permissions
      file:
        path: "/home/{{ item.0 }}/{{ item.1 }}"
        state: touch
        owner: "{{ item.0 }}"
      loop:
        - ["alice", "bob"]
        - ["file1.txt", "file2.txt"]
      loop_control:
        loop_var: item

02. Ansible Conditionals¶

Using the when clause¶

• Conditionals can be defined using the when clause:

---
- hosts: localhost
  tasks:
    - name: Install Apache only on Ubuntu
      apt:
        name: apache2
        state: present
      when: ansible_os_family == "Debian"

Complex conditionals¶

• Multiple conditionals can be combined with and, or, and not clauses:

---
- hosts: localhost
  tasks:
    - name: Restart service only if running
      service:
        name: nginx
        state: restarted
      when: ansible_os_family == "RedHat" and ansible_distribution_major_version | int >= 7

03. Combining loops and conditionals¶

• Loops and conditionals can be used together:

---
- hosts: localhost
  tasks:
    - name: Create users only if home directory does not exist
      user:
        name: "{{ item }}"
        state: present
      loop:
        - alice
        - bob
      when: not ansible_facts['getent_passwd'][item] is defined

04. Hands-on¶

• Try writing a playbook that installs different packages based on the OS family.
• Try to use as many parts as you can (external vars, vars, loops, conditions etc) while doing so.

05. Summary¶

• loop: (and the older with_items:) iterates a task over a list - the current item is accessed as {{ item }}
• when: conditionals accept Jinja2 expressions; the task is skipped when the condition evaluates to false
• ansible_facts['os_family'] and ansible_facts['distribution'] are commonly used in conditionals for cross-platform playbooks
• Loops and conditionals can be combined: when: is evaluated per iteration, not once for the whole loop
• loop_control: label: shortens verbose loop output by displaying only a meaningful variable instead of the full item dict