如何在变量未定义的情况下运行任务？

Question

我寻找到执行任务的方式，当ansible变量不是寄存器/未定义如

-- name: some task 
    command: sed -n '5p' "{{app.dirs.includes}}/BUILD.info" | awk '{print $2}' 
    when: (! deployed_revision) AND (!deployed_revision.stdout) 
    register: deployed_revision 

Answer 1

从ansible docs： 如果所需的变量尚未设置，您可以跳过或使用Jinja2的的定义会失败测试。例如：

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 

所以你的情况，when: deployed_revision is not defined应该工作