ansible——playbook conditions條件判斷

有些時候，我們需要進行一些條件判斷才決定是否執行某個操作，在playbook里面when語句幫我們解決了這個問題。

比如，如果節點的操作的系統為Debian那么就關機。

tasks:
  - name: "shut down Debian flavored systems"
    command: /sbin/shutdown -t now
    when: ansible_facts['os_family'] == "Debian"

當然還可以進行更加復雜的操作,and和or的邏輯判斷。
如果系統是centos6或者是Debian7，那么就關機。

tasks:
  - name: "shut down CentOS 6 and Debian 7 systems"
    command: /sbin/shutdown -t now
    when: (ansible_facts['distribution'] == "CentOS" and ansible_facts['distribution_major_version'] == "6") or
          (ansible_facts['distribution'] == "Debian" and ansible_facts['distribution_major_version'] == "7")

如果同時需要多個條件，那么可以這樣：

tasks:
  - name: "shut down CentOS 6 systems"
    command: /sbin/shutdown -t now
    when:
      - ansible_facts['distribution'] == "CentOS"
      - ansible_facts['distribution_major_version'] == "6"

其實等價於下面：

tasks:
  - name: "shut down CentOS 6 and Debian 7 systems"
    command: /sbin/shutdown -t now
    when: (ansible_facts['distribution'] == "CentOS" and ansible_facts['distribution_major_version'] == "6")

有時候你會得到一個變量，它是一個字符串，你可以對其進行數學運算：

tasks:
  - shell: echo "only on Red Hat 6, derivatives, and later"
    when: ansible_facts['os_family'] == "RedHat" and ansible_facts['lsb']['major_release']|int >= 6

你還可以根據變量值，來判斷：
變量值：

vars:
  epic: true

判斷：

tasks:
    - shell: echo "This certainly is epic!"
      when: epic

還可以循環：

tasks:
    - command: echo {{ item }}
      loop: [ 0, 2, 4, 6, 8, 10 ]
      when: item > 5

配合變量寄存器：

- name: test play
  hosts: all

  tasks:

      - shell: cat /etc/motd
        register: motd_contents

      - shell: echo "motd contains the word hi"
        when: motd_contents.stdout.find('hi') != -1