使用 jq 计算使用的卫星数量，并从 gpsd 输出中查看

Question

考虑这个 JSON:

{"class":"POLL","time":"2020-08-24T07:01:31.690Z","active":1,"tpv":[{"class":"TPV","tag":"ID8fac","device":"/dev/ttyM1","mode":3,"time":"2020-08-24T07:01:31.000Z","ept":0.005,"lat":-37.043028622,"lon":145.984996786,"alt":708.492,"epx":9.963,"epy":14.642,"epv":0.000,"speed":0.000,"climb":0.000,"eps":29.28}],"gst":[{"class":"GST","tag":"ID8fac","device":"/dev/ttyM1","time":"1970-01-01T00:00:00.000Z","rms":0.000,"major":0.000,"minor":0.000,"orient":0.000,"lat":0.000,"lon":0.000,"alt":0.000}],"sky":[{"class":"SKY","tag":"ID8fac","device":"/dev/ttyM1","xdop":0.66,"ydop":0.98,"vdop":0.00,"tdop":1.00,"hdop":0.00,"gdop":1.00,"pdop":0.00,"satellites":[{"PRN":17,"el":42,"az":137,"ss":43,"used":true},{"PRN":12,"el":27,"az":241,"ss":44,"used":true},{"PRN":24,"el":53,"az":247,"ss":46,"used":true},{"PRN":6,"el":55,"az":54,"ss":36,"used":true},{"PRN":15,"el":10,"az":307,"ss":40,"used":true},{"PRN":2,"el":31,"az":358,"ss":37,"used":true},{"PRN":28,"el":20,"az":89,"ss":35,"used":true},{"PRN":7,"el":10,"az":52,"ss":31,"used":false},{"PRN":19,"el":64,"az":148,"ss":45,"used":true},{"PRN":13,"el":10,"az":338,"ss":29,"used":false},{"PRN":15,"el":18,"az":297,"ss":33,"used":true},{"PRN":22,"el":10,"az":17,"ss":39,"used":false}]}]}

我有兴趣解析上面 JSON 中的卫星数组（下面提取）并返回两个数字：卫星数和使用的卫星数。例如：7 12

[
  {
    "PRN": 17,
    "el": 42,
    "az": 137,
    "ss": 43,
    "used": true
  },
  {
    "PRN": 12,
    "el": 27,
    "az": 241,
    "ss": 44,
    "used": true
  },
  {
    "PRN": 24,
    "el": 53,
    "az": 247,
    "ss": 46,
    "used": true
  },
  {
    "PRN": 6,
    "el": 55,
    "az": 54,
    "ss": 36,
    "used": true
  },
  {
    "PRN": 15,
    "el": 10,
    "az": 307,
    "ss": 40,
    "used": true
  },
  {
    "PRN": 2,
    "el": 31,
    "az": 358,
    "ss": 37,
    "used": true
  },
  {
    "PRN": 28,
    "el": 20,
    "az": 89,
    "ss": 35,
    "used": true
  },
  {
    "PRN": 7,
    "el": 10,
    "az": 52,
    "ss": 31,
    "used": false
  },
  {
    "PRN": 19,
    "el": 64,
    "az": 148,
    "ss": 45,
    "used": true
  },
  {
    "PRN": 13,
    "el": 10,
    "az": 338,
    "ss": 29,
    "used": false
  },
  {
    "PRN": 15,
    "el": 18,
    "az": 297,
    "ss": 33,
    "used": true
  },
  {
    "PRN": 22,
    "el": 10,
    "az": 17,
    "ss": 39,
    "used": false
  }
]

目前我只能弄清楚如何解析一个值，而不是一次解析两个值；这就是我所拥有的：

jq -r '[ .sky[] | .satellites[]| select(.used == true )| "\( .PRN )" ] |length'

输出使用的卫星数量，例如 7。

为了完整起见，如果它可能对某人有所帮助，我将按如下方式在 bash 中轮询 gpsd。此 returns 一个 JSON 结构，如 post 开头所示：

timeout 1 grep -m1 satellites < <(printf '%s\n' '?WATCH={"enable":true,"json":true};?POLL;' | nc 127.0.0.1 2947)

Answer 1

对于呈现的输入：

$ jq -r '.sky[].satellites | ( [ .[] | select(.used == true) ] | length ), length'
9
12

或者也许（但您也可以将其通过管道传输到 paste -sd" "）：

$ jq -r '.sky[].satellites | ( [ .[] | select(.used == true) ] | length | tostring) + " " + (length|tostring)'
9 12

使用 jq 计算使用的卫星数量，并从 gpsd 输出中查看

Using jq to count number of satellites used and in view from gpsd output

json

gpsd

jq