amazon-web-services - AWS cli JMESpath 查询标签值

Question

作为我的 previous question 的后续行动，我无法让标签在这种类型的输出中正常工作。我想打印一个表格，其中每个属性都是一行。这是我期望的样子:

% aws --output table ec2 describe-instances --instance-id $id --query "Reservations[].Instances[0].[{ Property: 'Type', Value: InstanceType }]"         
-------------------------------
|      DescribeInstances      |
+-----------+-----------------+
| Property  |      Value      |
+-----------+-----------------+
|  Type     |  g4dn.12xlarge  |
+-----------+-----------------+

但是标签名称看起来像这样:

% aws --output table ec2 describe-instances --instance-id $id --query "Reservations[].Instances[0].[{ Property: 'Name', Value: Tags[?Key =='Name'].Value }]"   
-------------------
|DescribeInstances|
+-----------------+
|    Property     |
+-----------------+
|  Name           |
+-----------------+
||     Value     ||
|+---------------+|
||  Elliott-TKD  ||
|+---------------+|

标签值是正确的，但格式很奇怪，当与更多其他行组合时，表格会变得非常难看。

Answer 1

查询的过滤器部分 ( [?Key == 'Name'] ) 正在创建 JMESPath 描述为 projection 的内容.
您必须重置此投影才能从中提取单个字符串。
可以使用 pipes 来重置投影.

Projections are an important concept in JMESPath. However, there are times when projection semantics are not what you want. A common scenario is when you want to operate of the result of a projection rather than projecting an expression onto each element in the array.For example, the expression people[*].first will give you an array containing the first names of everyone in the people array. What if you wanted the first element in that list? If you tried people[*].first[0] that you just evaluate first[0] for each element in the people array, and because indexing is not defined for strings, the final result would be an empty array, []. To accomplish the desired result, you can use a pipe expression, <expression> | <expression>, to indicate that a projection must stop.

^{来源:https://jmespath.org/tutorial.html#pipe-expressions}

因此您的问题非常接近他们在文档中描述的内容，并且可以使用以下方法重置该投影:

Tags[?Key =='Name']|[0].Value 

或者，用:

Tags[?Key =='Name'].Value | [0]

这是两个完全相同的查询。

给定 JSON:

{
  "Reservations": [
    {
      "Instances": [
        {

          "Tags": [
            {
              "Key": "Name",
              "Value": "Elliott-TKD"
            },
            {
              "Key": "Foo",
              "Value": "Bar"
            }
          ]
        }
      ]
    }
  ]
}

查询

Reservations[].Instances[0].[{ Property: `Name`, Value: Tags[?Key == `Name`]|[0].Value }]

会给出预期

[
  [
    {
      "Property": "Name",
      "Value": "Elliott-TKD"
    }
  ]
]

所以它会在您的表格中正确呈现

------------------------------
|      DescribeInstance      |
+------------+---------------+
|  Property  |     Value     |
+------------+---------------+
|    Name    |  Elliott-TKD  |
+------------+---------------+