如何在jq中的地图数组中求和? [英] How do I sum the values in an array of maps in jq?

问题描述

给出以下格式的JSON流:

Given a JSON stream of the following form:

{ "a": 10, "b": 11 } { "a": 20, "b": 21 } { "a": 30, "b": 31 }

我想对每个对象中的值求和并输出一个对象，即:

I would like to sum the values in each of the objects and output a single object, namely:

{ "a": 60, "b": 63 }

我猜想这可能需要将上面的对象列表展平为[name, value]对的数组，然后使用reduce对值求和，但是使用reduce的语法文档非常糟糕. /p>

I'm guessing this will probably require flattening the above list of objects into a an array of [name, value] pairs and then summing the values using reduce but the documentation of the syntax for using reduce is woeful.

推荐答案

除非您的jq具有inputs，否则您将不得不使用-s标志将对象吸干.然后，您必须进行大量的操作:

Unless your jq has inputs, you will have to slurp the objects up using the -s flag. Then you'll have to do a fair amount of manipulation:

1. 每个对象都需要映射到键/值对
2. 将线对平整为单个阵列
3. 通过密钥将配对分组
4. 将累积值的每个组映射到单个键/值对
5. 将对映射回对象

map(to_entries)
    | add
    | group_by(.key)
    | map({
          key: .[0].key,
          value: map(.value) | add
      })
    | from_entries

---

使用jq 1.5可以大大改善这一点:您可以消除拖尾的感觉，而直接阅读inputs.

$ jq -n '
reduce (inputs | to_entries[]) as {$key,$value} ({}; .[$key] += $value)
' input.json

由于我们只是累加了每个对象中的所有值，因此遍历所有输入的键/值对并将它们加起来会更容易.

Since we're simply accumulating all the values in each of the objects, it'll be easier to just run through the key/value pairs of all the inputs, and add them all up.

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