k3s/docs/user-guide/jsonpath.md

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<h2>PLEASE NOTE: This document applies to the HEAD of the source tree</h2>

If you are using a released version of Kubernetes, you should
refer to the docs that go with that version.

<strong>
The latest 1.0.x release of this document can be found
[here](http://releases.k8s.io/release-1.0/docs/user-guide/jsonpath.md).

Documentation for other releases can be found at
[releases.k8s.io](http://releases.k8s.io).
</strong>
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# JSONPath template syntax

JSONPath template is composed of JSONPath expressions enclosed by {}.
And we add three functions in addition to the original JSONPath syntax:

1. The `$` operator is optional since the expression always start from the root object by default.
2. We can use `""` to quote text inside JSONPath expression.
3. We can use `range` operator to iterate list.


The result object is printed as its String() function.

Given the input:

```json 
{
  "kind": "List",
  "items":[
    {
      "kind":"None",
      "metadata":{"name":"127.0.0.1"},
      "status":{
        "capacity":{"cpu":"4"},
        "addresses":[{"type": "LegacyHostIP", "address":"127.0.0.1"}]
      }
    },
    {
      "kind":"None",
      "metadata":{"name":"127.0.0.2"},
      "status":{
        "capacity":{"cpu":"8"},
        "addresses":[
          {"type": "LegacyHostIP", "address":"127.0.0.2"},
          {"type": "another", "address":"127.0.0.3"}
        ]
      }
    }
  ],
  "users":[
    {
      "name": "myself",
      "user": {}
    },
    {
      "name": "e2e",
      "user": {"username": "admin", "password": "secret"}
    }
  ]
}
```

Function | Description        | Example            | Result
---------|--------------------|--------------------|------------------
text     | the plain text     | kind is {.kind}    | kind is List
""       | quote              | {"{"}              | {
@        | the current object | {@}                | the same as input
. or []  | child operator     | {.kind} or {['kind']}| List
..       | recursive descent  | {..name}           | 127.0.0.1 127.0.0.2 myself e2e
*        | wildcard. Get all objects| {.items[*].metadata.name} | [127.0.0.1 127.0.0.2]
[start:end :step] | subscript operator | {.users[0].name}| myself
[,]      | union operator     | {.items[*]['metadata.name', 'status.capacity']} | 127.0.0.1 127.0.0.2 map[cpu:4] map[cpu:8]
?()      | filter             | {.users[?(@.name=="e2e")].user.password} | secret
range, end | iterate list | {range .items[*]}[{.metadata.name}, {.status.capacity}] {end} | [127.0.0.1, map[cpu:4]] [127.0.0.2, map[cpu:8]]




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