Ansible:如何从另一个变量构造一个变量，然后获取它的值 [英] Ansible: how to construct a variable from another variable and then fetch it's value

问题描述

这是我的问题，我需要使用一个变量target_host"，然后将_host"附加到它的值以获得另一个我需要其值的变量名称.如果你看看我的剧本.任务 nbr 1,2,3 获取变量的值，但是 nbr 4 无法实现我的预期.有没有其他方法可以在ansible中实现相同的目标?

Here is my problem I need to use one variable 'target_host' and then append '_host' to it's value to get another variable name whose value I need. If you look at my playbook. Task nbr 1,2,3 fetch the value of variable however nbr 4 is not able to do what I expect. Is there any other way to achieve the same in ansible?

   ---
    - name: "Play to for dynamic groups"
      hosts: local 
      vars:
        - target_host: smtp
        - smtp_host: smtp.max.com
      tasks:
        - name: testing
          debug: msg={{ target_host }}
        - name: testing
          debug: msg={{ smtp_host }}
        - name: testing
          debug: msg={{ target_host }}_host
        - name: testing
          debug: msg={{ {{ target_host }}_host }}


Output:

TASK: [testing] *************************************************************** 
ok: [127.0.0.1] => {
    "msg": "smtp"
}

TASK: [testing] *************************************************************** 
ok: [127.0.0.1] => {
    "msg": "smtp.max.com"
}

TASK: [testing] *************************************************************** 
ok: [127.0.0.1] => {
    "msg": "smtp_host"
}

TASK: [testing] *************************************************************** 
ok: [127.0.0.1] => {
    "msg": "{{{{target_host}}_host}}"
}

推荐答案

你需要在它周围加上引号:

You need to put quotes around it:

- hosts: local
  vars: [ target_host: smtp ]
  tasks:
    debug: msg="{{ target_host }}_host"

-- 编辑 --

Kashyap 我需要比这多上一层.想象有另一个变量smtp_host"，我想在运行时使用另一个变量(target_host)并附加一个字符串'_host' 到它.= {{ {{ target_host }}_host }} – 最大

Kashyap I need to go one more level than this. Imagine there is another variable 'smtp_host' and I want to construct that variable at runtime using another variable(target_host) and attaching a string '_host' to it. = {{ {{ target_host }}_host }} – Max

我的错.阅读不够仔细.

My bad. Didn't read carefully enough.

这(AFAIK)是不可能的.阻止我们这样做的主要限制(无论您如何旋转)，是 ansible 中的变量扩展"是单遍过程，而您想要的需要多次传递.

This (AFAIK) isn't possible. The primary limitation that stops us doing this (no matter how you spin it), is 'variable expansion' in ansible is a single pass process and what you want requires multiple-passes.

我能想到的唯一[严重hacky]方法是:

Only [seriously hacky] ways I can think of are:

• 使用template从你的剧本动态创建剧本并执行它.
• 我听说 Jinja2 引擎会进行多次评估.可能是如果您将这些字符串放在模板中，然后使用 lookup('template', ...) 过滤器.不幸的是，我没有使用 Jinja2 模板的经验，所以不太确定这是否是一种选择.

• Create the playbook dynamically from your playbook using template and execute it.
• I heard that Jinja2 engine does multi-pass evaluation. May be if you put these strings in a template and then use the lookup('template', ...) filter. Unfortunately I have no experience with Jinja2 templates so not quite sure if this is even an option.

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