Conditionals

Ansible 提供控制流程，可以讓你根據條件來決定是否執行某個任務。

when

when 可以用來設定條件，當條件成立時，才會執行任務。

以下是一個簡單的範例：

- name: Install Nginx
  hosts: web_servers
  become: true
  tasks:
    - name: Install Nginx on Ubuntu
      ansible.builtin.apt:
        name: nginx
        state: latest
      when: ansible_distribution == 'Ubuntu'

    - name: Install Nginx on CentOS
      ansible.builtin.yum:
        name: nginx
        state: latest
      when: ansible_distribution == 'CentOS'

or 與 and

or 與 and 可以用來組合多個條件，例如：

- name: Install Nginx
  hosts: web_servers
  become: true
  tasks:
    - name: Install Nginx on Ubuntu
      ansible.builtin.apt:
        name: nginx
        state: latest
      when: ansible_distribution == "Ubuntu" or ansible_distribution == "Debian"

    - name: Install Nginx on CentOS
      ansible.builtin.yum:
        name: nginx
        state: latest
      when: ansible_distribution == "CentOS" or ansible_distribution == "RedHat"

loop

loop 可以用來迭代一個 list，例如：

- name: Install packages
  hosts: web_servers
  become: true
  tasks:
    - name: Install packages
      ansible.builtin.apt:
        name: ""
        state: latest
      loop:
        - nginx
        - apache2
        - php

你可以結合剛剛的 when 一起使用，例如：

- name: Install Software
  hosts: all
  vars:
    - packages:
        - name: nginx
          required: true
        - name: apache2
          required: false
        - name: php
          required: true
  tasks:
    - name: Install  ""
      ansible.builtin.apt:
        name: ""
        state: latest
      loop: ""
      when: item.required == true

register

register 可以將執行任務後的輸出結果存到變數中，例如：

- name: Check status of a service and email if its down
  hosts: localhost
  tasks:
    - ansible.builtin.command: service httpd status
      register: result

    - community.general.mail:
        to: example@mail.com
        subject: "Service is down"
        body: ""
      when: result.stdout.find('down') != -1