使用 jq 查询嵌套的 json

Question

I have the json file about.json as below

{
  "build": {
    "tag": "189",
    "buildtime": "2019-07-19-08-05"
  },
  "microservices": [
    {
      "appId": "builds",
      "imageName": "build-server:8",
      "volumesFrom": []
    },
    {
      "appId": "studio",
      "imageName": "tci-webserver:4074",
      "volumesFrom": [
        "tci-download-studio:xxx"
      ]
    },
    {
      "appId": "site",
      "imageName": "site:22",
      "volumesFrom": null
    }
  ]
}

I want to substitute value for volumesFrom for for example for first appId: "builds", but I am not able to fetch the key in the first place. Could anyone help me with the command to do this.

I have the value stored in volumes variable. I want to assign this variable as a value to volumesFrom key for first appId:builds.

I tried accessing the volumesFrom object using syntax such as

jq .microservices.volumesFrom about.json

jq .microservices.[0].volumesfrom

But none seems to fetch the key which I am expecting.

Answer 1

First you have to find the microservice object of interest:

.microservices[] | select(.appId == "builds")

Then with that, you could then update the volumesFrom value:

(.microservices[] | select(.appId == "builds")).volumesFrom = ...

https://jqplay.org/s/zLsEYAQrFC