如何解析JSON来测试嵌套键的字符串值？

Question

例如，下面是我的程序的输出(bspwm，如果您想知道的话)：

{
  "id": 29360131,
  "splitType": "vertical",
  "splitRatio": 0.5,
  "birthRotation": 90,
  "vacant": true,
  "sticky": false,
  "private": false,
  "locked": false,
  "presel": null,
  "rectangle": {
    "x": 0,
    "y": 0,
    "width": 1920,
    "height": 1200
  },
  "firstChild": null,
  "secondChild": null,
  "client": {
    "className": "Termite",
    "instanceName": "termite",
    "borderWidth": 1,
    "state": "floating",
    "lastState": "tiled",
    "layer": "normal",
    "lastLayer": "normal",
    "urgent": false,
    "visible": true,
    "icccmFocus": true,
    "icccmInput": true,
    "minWidth": 10,
    "maxWidth": 0,
    "minHeight": 19,
    "maxHeight": 0,
    "wmStatesCount": 0,
    "wmState": [],
    "tiledRectangle": {
      "x": 0,
      "y": 0,
      "width": 958,
      "height": 1198
    },
    "floatingRectangle": {
      "x": 638,
      "y": 394,
      "width": 642,
      "height": 410
    }
  }
}

我想看看"state"是不是"tiling"。在这种情况下，它是"floating"。

Answer 1

更好的选择是使用JSON解析器。

如果您坚持使用grep：

假设您的grep支持PCRE (-P)：

bspwm | grep -Po '"state":\K[^,]*'

这将得到键"state"的值(带有引号)。

如果您不希望周围的引号围绕键：

bspwm | grep -Po '"state":"\K[^"]*'

例如：

% grep -Po '"state":\K[^,]*' <<<'{"id":29360131,"splitType":"vertical","splitRatio":0.500000,"birthRotation":90,"vacant":true,"sticky":false,"private":false,"locked":false,"presel":null,"rectangle":{"x":0,"y":0,"width":1920,"height":1200},"firstChild":null,"secondChild":null,"client":{"className":"Termite","instanceName":"termite","borderWidth":1,"state":"floating","lastState":"tiled","layer":"normal","lastLayer":"normal","urgent":false,"visible":true,"icccmFocus":true,"icccmInput":true,"minWidth":10,"maxWidth":0,"minHeight":19,"maxHeight":0,"wmStatesCount":0,"wmState":[],"tiledRectangle":{"x":0,"y":0,"width":958,"height":1198},"floatingRectangle":{"x":638,"y":394,"width":642,"height":410}}'

"floating"


% grep -Po '"state":"\K[^"]*' <<<'{"id":29360131,"splitType":"vertical","splitRatio":0.500000,"birthRotation":90,"vacant":true,"sticky":false,"private":false,"locked":false,"presel":null,"rectangle":{"x":0,"y":0,"width":1920,"height":1200},"firstChild":null,"secondChild":null,"client":{"className":"Termite","instanceName":"termite","borderWidth":1,"state":"floating","lastState":"tiled","layer":"normal","lastLayer":"normal","urgent":false,"visible":true,"icccmFocus":true,"icccmInput":true,"minWidth":10,"maxWidth":0,"minHeight":19,"maxHeight":0,"wmStatesCount":0,"wmState":[],"tiledRectangle":{"x":0,"y":0,"width":958,"height":1198},"floatingRectangle":{"x":638,"y":394,"width":642,"height":410}}'

floating

Answer 2

使用像吉顺这样的专用JSON解析器是一种更健壮的方法：

jshon -e client -e state -u < file             
floating