如何用'jq'总结包含百分比的字符串字段? [英] How to sum up string fields that contain percentages with 'jq'?

问题描述

我有一个JSON文件，该文件以百分比的形式跟踪表的列宽.所以输入文件columns.json看起来像这样:

I have a JSON file that's keeping track of column widths for a table as percentages. So the input file, columns.json, looks something like this:

[
  {
    "name": "Column A",
    "width": "33%"
  },
  {
    "name": "Column B",
    "width": "33%"
  },
  {
    "name": "Column C",
    "width": "33%"
  },
  {
    "name": "Column D",
    "visible": false
  }
]

某些列未显示，因此没有宽度(jq '.[].width将返回这些宽度)，然后还会出现百分号.否则，我可能会使用munge | munge | paste -sd+ | bc，这通常是我在shell中进行汇总的方法，但是在这里这似乎很愚蠢，因为jq 应该能够自己执行此操作.

Some columns are not displayed and therefore don't have widths (jq '.[].width will return nulls for these), and then there's also the issue of the percent signs. Otherwise I might've used munge | munge | paste -sd+ | bc, which is usually what I use for summing things up in the shell, but that seems stupid here because jq ought to be able to do this by itself.

因此仅使用jq ，我该如何总结此文件 eg 中的width字段，以确保它们不超过100％ ?

So using only jq, how can I sum up the width fields from this file, e.g., to make sure they don't exceed 100%?

我在这里使用select(.)过滤掉没有.width的记录，然后去除百分号:

I use select(.) here to filter out records that don't have a .width, then get rid of the percent sign:

jq '[.[].width | select(.) | sub("%"; "")] | add' columns.json

…但这只是连接字符串并返回"333333".

…but that just concatenates the strings and returns "333333".

我没有看到"typecast"一词.在jq手册页中，所以我认为也许会进行类型推断，在正确的上下文中将看起来像数字的字符串视为数字:

I didn't see any mention of the word "typecast" in the jq man page, so I thought maybe it would do type inference, treating a string that looks like a number as a number in the right context:

jq '[.[].width | select(.) | sub("%"; "") | .+0] | add' columns.json

...但是这只会产生错误消息，例如:

…but that just yields and error message like:

jq: error (at columns.json:18): string ("33") and number (0) cannot be added

推荐答案

一个简短的替代方法:

map(.width[:-1] | tonumber?) | add

^在线演示

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