Use JSONPATH to get configmap value

Question

How can I retrieve a configmap value using jsonpath?

I'm trying to retrieve the value of haproxy.cfg from my configmap, but I can't get it just right:

kubectl get cm -l app=haproxy -o jsonpath="{['items'][0]['data']['haproxy.cfg']}"

The above returns no results. But I can definitely get the configmap if I leave off the haproxy.cfg:

kubectl get cm -l app=haproxy -o jsonpath="{['items'][0]['data']}"

Yields:

map[haproxy.cfg:
global
  user root
  group root
  maxconn 256
...
]

I can use jq:

kubectl get cm -l app=haproxy -o json | jq -r '.items[0].data["haproxy.cfg"]'

which yields exactly what I want:


global
  user root
  group root
  maxconn 256

If you need help creating your ConfigMap, here's the manifest for the one I am using:

apiVersion: v1
data:
    haproxy.cfg: "\nglobal\n  user root\n  group root\n  maxconn 256\n\n"
kind: ConfigMap
metadata:
    annotations:
      meta.helm.sh/release-name: haproxy
      meta.helm.sh/release-namespace: haproxy
    labels:
      app: haproxy
      app-version: 2.4.0
      app.kubernetes.io/managed-by: Helm
      heritage: Helm
      release: haproxy
      version: 0.0.3
    name: haproxy

try {['items'][0]['data'][0]} or can you provide manifest file to create the cm to play around ? — P....
– P...., Commented Jun 15, 2021 at 23:32

Mark · Accepted Answer · 2021-06-16 21:52:50Z

4

Escape the . inside single quotes

kubectl get cm -l app=haproxy -o jsonpath="{.items[0].data['haproxy\.cfg']}"

* This didn't work a long time ago, pre 1.5. Then you needed to use go-template formatting.

edited Jun 16, 2021 at 21:52

Mark

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answered Jun 16, 2021 at 2:11

Matt

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Comments

Mikołaj Głodziak · Accepted Answer · 2021-06-16 11:28:04Z

2

I have created simple configmap.

kubectl get cm game-config-example -o json

returns:

{
    "apiVersion": "v1",
    "data": {
        "game.properties": "enemies=aliens\nlives=3\nenemies.cheat=true\nenemies.cheat.level=noGoodRotten\nsecret.code.passphrase=UUDDLRLRBABAS\nsecret.code.allowed=true\nsecret.code.lives=30",
        "ui.properties": "color.good=purple\ncolor.bad=yellow\nallow.textmode=true\nhow.nice.to.look=fairlyNice\n"
    },
    "kind": "ConfigMap",
    "metadata": {
        "creationTimestamp": "2021-06-16T10:08:28Z",
        "name": "game-config-example",
        "namespace": "default",
        "resourceVersion": "24666141",
        "selfLink": "/api/v1/namespaces/default/configmaps/game-config-example",
        "uid": "3d6d2ba0-8f5a-43a7-953b-91a62dbcd248"
    }
}

I have tested solution with escaping . characters on versions 1.19 and 1.21. Both works fine.

kubectl get cm game-config-example -o jsonpath="{['data']['ui\.properties']}"

gives right output:

color.good=purple
color.bad=yellow
allow.textmode=true
how.nice.to.look=fairlyNice

Same result I can achive if I use:

go-template:

kubectl get cm game-config-example -o 'go-template={{index .data "ui.properties" }}'

jq command:

kubectl get cm game-config-example -o json | jq -r '.data."ui.properties"'

You can see also this issue - JSONpath fails to return keys containing dots in a map.

answered Jun 16, 2021 at 11:28

Mikołaj Głodziak

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2 Comments

Mark Over a year ago

I was able to get your approach to work when I selected the CM by name (and thus did not receive a list back from kube). Here's what worked for me kubectl get cm haproxy -o 'go-template={{index .data "haproxy.cfg" }}'

Mark Over a year ago

Selecting my cm by label, I was also able to get the gotemplate to wokr like this kubectl get cm -l app=haproxy -o 'go-template={{ range .items }}{{index .data "haproxy.cfg" }}{{ end }}' - thanks for the go-template suggestion.

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