這個when應該不能算是一個[模塊][1] Ansible提供when語句，可以控制任務的執行流程。 一個很簡單的when語句的例子 ~~~ tasks: - name: "shutdown Debian flavored systems" command: /sbin/shutdown -t now when: ansible_os_family == "Debian ~~~ 在符合語句中也可以使用小括號: ~~~ tasks: - name: "shutdown CentOS 6 and 7 systems" command: /sbin/shutdown -t now when: ansible_distribution == "CentOS" and (ansible_distribution_major_version == "6" or ansible_distribution_major_version == "7") ~~~ 在`when`語句中也可以使用過濾器。如，我們想跳過一個語句執行中的錯誤，但是后續的任務的執行需要由該任務是否成功執行決定： ~~~ tasks: - command: /bin/false register: result ignore_errors: True - command: /bin/something when: result|failed - command: /bin/something_else when: result|success - command: /bin/still/something_else when: result|skipped ~~~ 有時候需要將一個字符串的變量轉換為整數來進行數字比較： ~~~ tasks: - shell: echo "only on Red Hat 6, derivatives, and later" when: ansible_os_family == "RedHat" and ansible_lsb.major_release|int >= 6 ~~~ 在playbooks和inventory中定義的變量都可以使用，如，需要根據一個變量的bool值決定是否執行該任務： ~~~ vars: epic: true ~~~ 條件語句： ~~~ tasks: - shell: echo "This certainly is epic!" when: epic ~~~ ~~~ tasks: - shell: echo "This certainly isn't epic!" when: not epic ~~~ 如果引用的變量沒有被定義，使用Jinja2的`defined`測試，可以跳過或者是拋出錯誤： ~~~ tasks: - shell: echo "I've got '{{ foo }}' and am not afraid to use it!" when: foo is defined - fail: msg="Bailing out. this play requires 'bar'" when: bar is not defined ~~~ [1]:http://docs.ansible.com/ansible/latest/playbooks_conditionals.html#the-when-statement