`jq` cheatsheet

ℹ️ The examples here use a JSON output from kubectl:

href="#__codelineno-0-1">kubectl get po -o json | jq -r pan> "apiVersion": "v1", "items": [ { "apiVersion": "v1", "kind": "Pod", "metadata": { "name": "bar-app", "namespace": "default", }, "spec": { "containers": [ { "image": "kicbase/echo-server:1.0", "name": "bar-app", ... }, ], ... } }, ... ]

Data Extraction

Extract specific attribute

jq '.apiVersion'
"v1"

Iterative extract attributes

jq '.items[].metadata.name'
jq '.items[] | .metadata.name'
"bar-app"
"foo-app"
"kubes-bootcamp-7c5b8c477c-6bkvc"

Recursive extract attributes

jq '.items[].spec.containers[].image'
jq '.items[] | .spec.containers[].image'
"kicbase/echo-server:1.0"
"wmax641/test-app:latest"
"kicbase/echo-server:1.0"
"gcr.io/google-samples/kubernetes-bootcamp:v1"

Extract multiple attributes

jq '.items[].spec.containers[] | {name, image}'

{
  "name": "bar-app",
  "image": "kicbase/echo-server:1.0"
}
{
  "name": "wma-test-app",
  "image": "wmax641/test-app:latest"
}
{
  "name": "foo-app",
  "image": "kicbase/echo-server:1.0"
}
{
  "name": "kubes-bootcamp",
  "image": "gcr.io/google-samples/kubernetes-bootcamp:v1"
}

jq '.items[].spec.containers[] | {name, image} | join(",")'

"bar-app,kicbase/echo-server:1.0"
"wma-test-app,wmax641/test-app:latest"
"foo-app,kicbase/echo-server:1.0"
"kubes-bootcamp,gcr.io/google-samples/kubernetes-bootcamp:v1"

However, to extract multiple attributes at different nest levels, employ this strategy:
While traversing down the nested structure, save certain attributes as a variable before continuing traversal. Then reconstruct the output referencing the variables

jq '.items[] | .metadata.name as $POD_NAME | 
    .spec.containers[] | {"pod":$POD_NAME, name, image}'

{
  "pod": "kubes-bootcamp-7b95d6fbcc-dll6x",
  "name": "kubes-bootcamp",
  "image": "gcr.io/google-samples/kubernetes-bootcamp:v1"
}
{
  "pod": "kubes-bootcamp-7b95d6fbcc-dll6x",
  "name": "kubes-bootcamp-thirdwheel",
  "image": "alpine:latest"
}
{
  "pod": "kubes-bootcamp-7b95d6fbcc-sgcwt",
  "name": "kubes-bootcamp",
  "image": "gcr.io/google-samples/kubernetes-bootcamp:v1"
}
{
  "pod": "kubes-bootcamp-7b95d6fbcc-sgcwt",
  "name": "kubes-bootcamp-thirdwheel",
  "image": "alpine:latest"
}

Slice an array

Similar to python indexing. Outputs into a separate list, so have to re-reference the new list

jq '.items[0:2] | .[].metadata.name'
"bar-app"
"foo-app"

Functions

Get length of an array

jq '.items[].spec.containers | length'
2
1
1

Get keys for attribute

jq '.items[1].spec.containers[0] | keys '
[
  "image",
  "imagePullPolicy",
  "name",
  "resources",
  "terminationMessagePath",
  "terminationMessagePolicy",
  "volumeMounts"
]

jq cheatsheet