如何在ansible中未定义变量的情况下运行任务？
如何在ansible中未定义变量的情况下运行任务？
提问于 2015-05-08 17:08:48
我正在寻找一种方法来执行任务时，可用变量不是寄存器/undefined，例如
-- 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回答 3
Stack Overflow用户
回答已采纳
发布于 2015-05-08 17:28:22
在ansible docs中:如果没有设置所需的变量，则可以使用JJIA2的已定义测试跳过或失败。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因此，在您的情况下，when: deployed_revision is not defined应该可以工作
Stack Overflow用户
发布于 2018-04-10 16:38:52
根据最新的Ansible version2.5，要检查是否定义了变量，并根据此检查是否要运行任何任务，请使用undefined关键字。
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 undefinedStack Overflow用户
发布于 2018-08-16 04:30:07
严格声明，您必须检查以下所有项:已定义、非空和非无。
对于“正常”变量，如果定义并设置或不设置，则会产生差异。请参阅下面示例中的foo和bar。两者都已定义，但仅设置了foo。
另一方面，注册变量被设置为运行命令的结果，并且根据模块的不同而不同。它们大多是json结构。您可能必须检查您感兴趣的子元素。请参见以下示例中的xyz和xyz.msg：
cat > test.yml <<EOF
- hosts: 127.0.0.1
vars:
foo: "" # foo is defined and foo == '' and foo != None
bar: # bar is defined and bar != '' and bar == None
tasks:
- debug:
msg : ""
register: xyz # xyz is defined and xyz != '' and xyz != None
# xyz.msg is defined and xyz.msg == '' and xyz.msg != None
- debug:
msg: "foo is defined and foo == '' and foo != None"
when: foo is defined and foo == '' and foo != None
- debug:
msg: "bar is defined and bar != '' and bar == None"
when: bar is defined and bar != '' and bar == None
- debug:
msg: "xyz is defined and xyz != '' and xyz != None"
when: xyz is defined and xyz != '' and xyz != None
- debug:
msg: "{{ xyz }}"
- debug:
msg: "xyz.msg is defined and xyz.msg == '' and xyz.msg != None"
when: xyz.msg is defined and xyz.msg == '' and xyz.msg != None
- debug:
msg: "{{ xyz.msg }}"
EOF
ansible-playbook -v test.yml页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/30119973
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