Ansible如何准确解析布尔变量? [英] How Exactly Does Ansible Parse Boolean Variables?

问题描述

在Ansible中，可以在多个地方定义变量:在清单中，在剧本中，在变量文件中，等等.有人可以解释我的以下发现吗?

In Ansible, there are several places where variables can be defined: in the inventory, in a playbook, in variable files, etc. Can anyone explain the following observations that I have made?

1. 在清单中定义布尔变量时，必须将其大写(即True/False)，否则(即true/false)将不会被解释为布尔值，而是字符串.
2. 在任何YAML格式的文件(剧本，角色等)中，True/False和true/false均被解释为布尔值.

例如，我在清单中定义了两个变量:

For example, I defined two variables in an inventory:

abc=false
xyz=False

在调试角色中的这些变量的类型时...

And when debugging the type of these variables inside a role...

- debug:
    msg: "abc={{ abc | type_debug }}  xyz={{ xyz | type_debug }}"

...然后abc变为unicode，但xyz被解释为bool:

... then abc becomes unicode but xyz is interpreted as a bool:

ok: [localhost] => {
    "msg": "abc=unicode  xyz=bool"
}

但是，在剧本中定义相同的变量时，如下所示:

However, when defining the same variables in a playbook, like this:

  vars:
    abc: false
    xyz: False

...则两个变量都被识别为bool.

... then both variables are recognized as bool.

在生产上执行一本剧本之后，由于库存中的变量设置为"false"而不是"False"，因此我不得不意识到这是很难的事情.因此，我真的很想找到一个清晰的答案，以了解Ansible如何理解布尔值以及它如何取决于变量的定义位置/方式.为了安全起见，我是否应该总是只使用大写的True/False?是否可以说YAML文件(格式为key: value)中的布尔值不区分大小写，而属性文件(格式为key=value)中的布尔值则区分大小写?任何更深刻的见解将不胜感激.

I had to realize this the hard way after executing a playbook on production, running something that should not have run because of a variable set to 'false' instead of 'False' in an inventory. Thus, I'd really like to find a clear answer about how Ansible understands Booleans and how it depends on where/how the variable is defined. Should I simply always use capitalized True/False to be on the safe side? Is it valid to say that booleans in YAML files (with format key: value) are case-insensitive, while in properties files (with format key=value) they are case-sensitive? Any deeper insights would be highly appreciated.

推荐答案

在YAML文件中定义的变量(剧本，vars_files和YAML格式的广告资源)

---

YAML原则

首先，由YAML解析器处理

以YAML编写的剧本，vars_files和库存文件.它为值存储了Boolean类型提供了几种别名:yes/no，true/false，on/off，在多种情况下定义:true/True/TRUE(因此它们并不区分大小写).

Variables defined in YAML files (playbooks, vars_files, YAML-format inventories)

---

YAML principles

Playbooks, vars_files, and inventory files written in YAML are processed by a YAML parser first. It allows several aliases for values which will be stored as Boolean type: yes/no, true/false, on/off, defined in several cases: true/True/TRUE (thus they are not truly case-insensitive).

YAML定义将可能的值指定为:

y|Y|yes|Yes|YES|n|N|no|No|NO
|true|True|TRUE|false|False|FALSE
|on|On|ON|off|Off|OFF

Ansible文档确认:

您还可以以几种形式指定布尔值(真/假):

You can also specify a boolean value (true/false) in several forms:

create_key: yes
needs_agent: no
knows_oop: True
likes_emacs: TRUE
uses_cvs: false

---

---

以INI格式的清单文件定义的变量

---

Python原理

当Ansible读取INI格式的广告资源时，它会处理变量使用Python内置类型:

---

---

Variables defined in INI-format inventory files

---

Python principles

When Ansible reads an INI-format inventory, it processes the variables using Python built-in types:

使用key=value语法传递的值将解释为Python文字结构(字符串，数字，元组，列表，字典，布尔值，无)或字符串.例如，var=FALSE将创建一个等于FALSE的字符串.

Values passed in using the key=value syntax are interpreted as Python literal structure (strings, numbers, tuples, lists, dicts, booleans, None), alternatively as string. For example var=FALSE would create a string equal to FALSE.

如果指定的值与字符串True或False(以大写字母开头)匹配，则将该类型设置为布尔值，否则将被视为字符串(除非与其他类型匹配).

If the value specified matches string True or False (starting with a capital letter) the type is set to Boolean, otherwise it is treated as string (unless it matches another type).

在CLI中作为Extra-vars传递的所有变量均为字符串类型.

All variables passed as extra-vars in CLI are of string type.

这篇关于Ansible如何准确解析布尔变量?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！