如何根据子项的jq值提取密钥 [英] How do I extract a key with jq based on its child values

问题描述

我正在尝试使用jq处理一些JSON.具体来说，我想要一个基于其子值的特定键.示例，给出:

I'm trying to process some JSON with jq. Specifically, I want a particular key, based on its child value. Example, given:

{
  "foo": {"primary": true, "blah": "beep"},
  "bar": {"primary": false, "blah": "narf"},
  "baz": {"primary": false, "blah": "poink"},
}

我想要字符串"foo"，因为这是其子值"primary"为true的键(由于生成的是JSON，因此我可以保证只有一个条目的primary = true.)

I want the string "foo", because that is the key whose child value "primary' is true. (I can guarantee that one and only one entry will have primary = true, due to what's generating the JSON.)

到目前为止，我能够管理的最好的事情是:

So far the best I've been able to manage is:

jq -r '.[] | select(.primary == true)'

但这将返回"foo"的值，而不是字符串"foo"本身.到目前为止，我一直在仔细阅读手册，但仍未找到一种方法来专门抓住钥匙.

But that returns the value of "foo", not the string "foo" itself. Digging through the manual so far I've not found a way to grab the key specifically.

您可以提供任何指针吗?

Any pointers you can provide?

推荐答案

您需要将对象拆分"为条目数组，例如

You need to "split" your object into an array of entries, e.g.

[
  {
    "key": "foo",
    "value": {
      "primary": true,
      "blah": "beep"
    }
  }
  //...
]

然后您可以使用.value.primary进行过滤，并使用.key映射结果:

Then you can filter with .value.primary and map the result with .key:

to_entries | map(select(.value.primary)  | .key)

返回:

[
  "foo"
]

或者只获取数组的第一项:(谢谢@nbari)

Or to get just the first item of the array: (Thanks @nbari)

to_entries | map(select(.value.primary)  | .key)[0]

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