判断语句 之 变量判断

参数	释义	示例
defined	变量已定义	when: username is defined
undefind	变量未定义	when: username is undfined
none	变量已定义未赋值	when: username is none

- hosts: all
  tasks:
  - name: test defined
    vars:
      username: test1
    debug:
      msg: "{{ username }} is defined"
    when: username is defined
  - name: test undefined
    vars:
    debug:
      msg: "username is undefined"
    when: username is undefined
  - name: test none
    vars:
      username:
    debug:
      msg: "{{username}} is none"
    when: username is none