Kubectl get JSONPath Support

External

• https://kubernetes.io/docs/reference/kubectl/jsonpath/

Internal

• kubectl
• JSONPath

Overview

kubectl get -o jsonpath='{<jsonpath-expression>}' ...

supports a JSONPath template, which consists in JSONPath expressions enclosed by curly braces.

kubectl get pod some-pod -o jsonpath='{.status.phase}'

More than one JSONPath expressions can be concatenated in a JSON template:

kubectl get pod some-pod -o jsonpath='the pod name {.metadata.name} and phase {.status.phase}'

The JSONPath expression are mainly used to:

• Filter the JSON content to only allow specific fields in the JSON object, using filter expressions.
• Format the output.

In addition to the original JSONPath syntax, kubectl provides the following extensions:

• The possibility to use double quotes to quote text inside JSONPath expressions.
• The availability of the range and end operators to iterate lists.

Note that when the result of the kubectl query contains more than one item, it is returned as a "List" top-level JSON Object, where individual results are element of an ".items" array:

{
  "apiVersion": "v1",
  "kind": "List",
  "metadata": {
    "resourceVersion": "..."
    ...
  }
  "items": [ 
    {
      "apiVersion": "v1",
      "kind": "Namespace", 
      ...
    },
    ...
  ]
}

The result should be processed as such:

kubectl get pods -o jsonpath="{.items[*]...}"

Syntax

$

• JSONPath $

Element Selection

Object Fields Selection

Individual Fields

JSONPath .field

The value of a specified field can be obtained with:

kubectl get pod <pod-name> -o jsonpath="{.status.phase}"

When more than one resource is returned as result, the result is a JSON "List" Object with an .items field, which can be queried as such:

kubectl get pods -o jsonpath="{.items[*].status.phase}"

Field Recursive Descent

All values for a specific field can be obtained recursively with:

JSONPath ..field (field recursive descent)

Array Element Selection

• JSONPath [0-based-index]
• JSONPath [index1, index2, ...]
• JSONPath [start:end], [start:]
• JSONPath [:n]
• JSONPath [-n:]

Wildcard

• JSONPath * (wildcard)

@

JSONPath @

Filter Expressions

[?(expression)]

JSONPath Filter Expressions

Organizatorium

Removing Leading and Trailing Single Quotes

... | sed -e 's/^'\''//' > ...

Get an Individual Attribute Only

TODO: https://gist.github.com/so0k/42313dbb3b547a0f51a547bb968696ba

kubectl ... -o jsonpath="{.items[?(@.spec.unschedulable)].metadata.name}"

Alternative, to explore and document:

kubectl get pods  --no-headers -o custom-columns=\":metadata.name\" ...

Filter Elements of an Array based on a Key Value

We assume that the elements of the array are maps, which contain the specified key:

kubectl ... -o jsonpath="{.users[?(@.name=="blue")].user.password}"
kubectl get pod ... -o jsonpath='{.items[0].spec.volumes[?(@.name=="vault")].hostPath.path}' 2>/dev/null

Select and Combine Two or More Elements

kubectl get pod \
-o jsonpath='{.items[0].spec.volumes[?(@.name=="A")].hostPath.path}'+'{.items[0].spec.volumes[?(@.name=="B")].hostPath.path}'

returns "/some/path/a+/some/path/b"

Same Element from Multiple Resources

kubectl get pod -o jsonpath='{.items[*].metadata.name}'

Array Length

jq Array Length

TODO

kubectl get pods -o=jsonpath='{.items[?(@.metadata.labels.name=="web")].metadata.name}'

Iterate over the Elements of an Array

kubectl get nodes -o jsonpath='{.items[*]}'

Iterate over the Elements of an Array and Select a Specific Key

kubectl get nodes -o jsonpath='{.items[*].status}'

Filter by an element:

kubectl get nodes -o jsonpath='{.items[*].status.addresses[?(@.type=="InternalIP")]}'

Print the element "address"

kubectl get nodes -o jsonpath='{.items[*].status.addresses[?(@.type=="InternalIP")].address}'