在when条件下如何使用变量替换? [英] How to use variable substitution in a when condition?

问题描述

我是新的ansible用户.我需要在任务的when条件中使用变量.我正在尝试使用home_directory变量，该变量定义为home_directory:"{{ansible_env.HOME}}"在vars/main.yaml文件中.

I'm a new ansible user. I need a variable in a task's when condition. I am trying to use home_directory variable, which is defined as home_directory: "{{ ansible_env.HOME }}" in the vars/main.yaml file.

我尝试使用类似以下的内容:

I tried to use something like following:

何时:{{home_directory}}/var_name ['var_key']！= command_output ['stdout']

when: {{ home_directory}}/var_name['var_key'] != command_output['stdout']

但是，我后来发现，不允许/建议使用Jinja模板{{}}或{%%}当条件.我还尝试了不带引号和{{}}的条件，但home_directory的值为不会在when条件下被替换.

However, I later found out that jinja templates {{}} or {%%} are not allowed/recommended in the when condition. I also tried condition without quotes and {{}} but home_directory value is not being replaced in the when condition.

有人可以告诉我我可以在这里做什么吗?

Could someone please tell me what I can do here?

推荐答案

但是，后来我发现在when条件下不允许/建议使用Jinja模板{{}}或{%%}.

However, I later found out that jinja templates {{}} or {%%} are not allowed/recommended in the when condition.

这是因为 when 的参数是在隐式模板上下文中求值的.换句话说，准确地编写您将在 {{......}} 标记中编写的内容，但是您不需要这些标记，因为上下文是命令固有的.

This is because the arguments to when are evaluated in an implicit template context. In other words, write exactly what you would write inside {{...}} markers, but you don't need the markers because the context is intrinsic to the command.

换句话说，代替:

when: {{ home_directory}}/var_name['var_key'] != command_output['stdout']

写:

when: home_directory ~ "/" ~ var_name['var-key'] != command_output['stdout']

其中〜是Jinja字符串连接运算符.

Where ~ is the Jinja string concatenation operator.

我们可以简化一下:

when: "%s/%s" % (home_directory, var_name.var_key) != command_output.stdout

这利用Linux字符串格式化语法将变量替换为字符串.

This takes advantage of Linux string formatting syntax to substitute variables into a string.

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