Usually, most Kubernetes objects are quite big as they have namespace, name, labels, template, spec and a bunch of other fields. When you need to get only one or several fields, it can get tedious scrolling up and down in your terminal looking for it :) Luckily, kubectl supports formatting your output using JSON path that allows you to specify the format and values yourself.
In the following example I will show how to format a Custom Resource output from the operator that I have recently wrote so it's easy to retrieve data from the status field.
First, let's see what data is available:
$ kubectl get webhookrelayforwards.forward.webhookrelay.com -o json
{
"apiVersion": "v1",
"items": [
{
"apiVersion": "forward.webhookrelay.com/v1",
"kind": "WebhookRelayForward",
"metadata": {
"annotations": {
"kubectl.kubernetes.io/last-applied-configuration": "{\"apiVersion\":\"forward.webhookrelay.com/v1\",\"kind\":\"WebhookRelayForward\",\"metadata\":{\"annotations\":{},\"name\":\"forward-to-jenkins\",\"namespace\":\"jenkins\"},\"spec\":{\"buckets\":[{\"inputs\":[{\"description\":\"Endpoint for GitHub\",\"name\":\"public-endpoint\",\"responseBody\":\"OK\",\"responseStatusCode\":200}],\"name\":\"jenkins-whr-operator\",\"outputs\":[{\"destination\":\"http://jenkins-operator-http-jenkins:8080/github-webhook/\",\"name\":\"jenkins\"}]}],\"image\":\"webhookrelay/webhookrelayd-ubi8:latest\"}}\n"
},
"creationTimestamp": "2020-07-05T12:52:11Z",
"generation": 2,
"name": "forward-to-jenkins",
"namespace": "jenkins",
"resourceVersion": "270615",
"selfLink": "/apis/forward.webhookrelay.com/v1/namespaces/jenkins/webhookrelayforwards/forward-to-jenkins",
"uid": "9d75809c-1795-45e2-a437-bb89b22bdac4"
},
"spec": {
"buckets": [
{
"inputs": [
{
"description": "Endpoint for GitHub",
"name": "public-endpoint",
"responseBody": "OK",
"responseStatusCode": 200
}
],
"name": "jenkins-whr-operator",
"outputs": [
{
"destination": "http://jenkins-operator-http-jenkins:8080/github-webhook/",
"name": "jenkins"
}
]
}
],
"image": "webhookrelay/webhookrelayd-ubi8:latest"
},
"status": {
"agentStatus": "Running",
"publicEndpoints": [
"https://k0yv9ip5sxxp55ncsu936k.hooks.webhookrelay.com"
],
"ready": true,
"routingStatus": "Configured"
}
}
],
"kind": "List",
"metadata": {
"resourceVersion": "",
"selfLink": ""
}
}
Here, if we want to grab just the value from publicEndpoints, we specify again the resource and additional jsonpath query:
$ kubectl get webhookrelayforwards.forward.webhookrelay.com forward-to-jenkins -o 'jsonpath={.status.publicEndpoints[0]}'
https://k0yv9ip5sxxp55ncsu936k.hooks.webhookrelay.com
Go ahead and try it on your own Kubernetes cluster! :)
You can find more examples in the official docs here: https://kubernetes.io/docs/reference/kubectl/jsonpath/.