Extract specific key from a json file in kubernetes configmap

Question

I have a k8s config map with json format data. Ex:

apiVersion: v1
kind: ConfigMap
metadata:
  name: xyz
  namespace: x
data:
  resources.json: |
    {
    "configsets":
    [
        {
            "key1":   "value1",
            "key2":
            [
                {
                    "machine":    value,
                    "id":     value
                },
                {
                    "machine":    value,
                    "id":     value
                },
                {
                    "machine":    value,
                    "id":     value,
                }
            ]
        }

I need the total number of the machines inside key2 as a variable in a bash script. How can I extract this information?

Answer 1

First of all, the resources.json is wrong and should be something like:

apiVersion: v1
kind: ConfigMap
metadata:
  name: xyz
data:
  resources.json: |
    {
    "configsets":
    [
        {
            "key1":   "value1",
            "key2": 
                [
                    {
                        "machine":    "value",
                        "id":     "value"
                    },
                    {
                        "machine":    "value",
                        "id":     "value"
                    },
                    {
                        "machine":    "value",
                        "id":     "value"
                    }
                ]
            
            
        }
    ]
    }

If so, then you can do:

kubectl get cm xyz -o jsonpath='{.data.resources\.json}' | jq '.configsets[0].key2|keys|length'

that will give you the number of objects inside the array thus the number of machines.

You need to have jq installed. e.g in Ubuntu: sudo apt-get install jq