100 lines
4.1 KiB
Markdown
100 lines
4.1 KiB
Markdown
---
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title: JSONPath Support
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content_template: templates/concept
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weight: 25
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---
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{{% capture overview %}}
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Kubectl supports JSONPath template.
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{{% /capture %}}
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{{% capture body %}}
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JSONPath template is composed of JSONPath expressions enclosed by curly braces {}.
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Kubectl uses JSONPath expressions to filter on specific fields in the JSON object and format the output.
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In addition to the original JSONPath template syntax, the following functions and syntax are valid:
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1. Use double quotes to quote text inside JSONPath expressions.
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2. Use the `range`, `end` operators to iterate lists.
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3. Use negative slice indices to step backwards through a list. Negative indices do not "wrap around" a list and are valid as long as `-index + listLength >= 0`.
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{{< note >}}
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- The `$` operator is optional since the expression always starts from the root object by default.
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- The result object is printed as its String() function.
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{{< /note >}}
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Given the JSON input:
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```json
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{
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"kind": "List",
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"items":[
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{
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"kind":"None",
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"metadata":{"name":"127.0.0.1"},
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"status":{
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"capacity":{"cpu":"4"},
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"addresses":[{"type": "LegacyHostIP", "address":"127.0.0.1"}]
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}
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},
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{
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"kind":"None",
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"metadata":{"name":"127.0.0.2"},
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"status":{
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"capacity":{"cpu":"8"},
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"addresses":[
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{"type": "LegacyHostIP", "address":"127.0.0.2"},
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{"type": "another", "address":"127.0.0.3"}
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]
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}
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}
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],
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"users":[
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{
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"name": "myself",
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"user": {}
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},
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{
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"name": "e2e",
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"user": {"username": "admin", "password": "secret"}
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}
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]
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}
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```
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Function | Description | Example | Result
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--------------------|---------------------------|-----------------------------------------------------------------|------------------
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`text` | the plain text | `kind is {.kind}` | `kind is List`
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`@` | the current object | `{@}` | the same as input
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`.` or `[]` | child operator | `{.kind}`, `{['kind']}` or `{['name\.type']}` | `List`
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`..` | recursive descent | `{..name}` | `127.0.0.1 127.0.0.2 myself e2e`
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`*` | wildcard. Get all objects | `{.items[*].metadata.name}` | `[127.0.0.1 127.0.0.2]`
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`[start:end:step]` | subscript operator | `{.users[0].name}` | `myself`
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`[,]` | union operator | `{.items[*]['metadata.name', 'status.capacity']}` | `127.0.0.1 127.0.0.2 map[cpu:4] map[cpu:8]`
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`?()` | filter | `{.users[?(@.name=="e2e")].user.password}` | `secret`
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`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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`''` | quote interpreted string | `{range .items[*]}{.metadata.name}{'\t'}{end}` | `127.0.0.1 127.0.0.2`
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Examples using `kubectl` and JSONPath expressions:
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```shell
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kubectl get pods -o json
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kubectl get pods -o=jsonpath='{@}'
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kubectl get pods -o=jsonpath='{.items[0]}'
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kubectl get pods -o=jsonpath='{.items[0].metadata.name}'
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kubectl get pods -o=jsonpath="{.items[*]['metadata.name', 'status.capacity']}"
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kubectl get pods -o=jsonpath='{range .items[*]}{.metadata.name}{"\t"}{.status.startTime}{"\n"}{end}'
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```
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On Windows, you must _double_ quote any JSONPath template that contains spaces (not single quote as shown above for bash). This in turn means that you must use a single quote or escaped double quote around any literals in the template. For example:
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```cmd
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C:\> kubectl get pods -o=jsonpath="{range .items[*]}{.metadata.name}{'\t'}{.status.startTime}{'\n'}{end}"
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C:\> kubectl get pods -o=jsonpath="{range .items[*]}{.metadata.name}{\"\t\"}{.status.startTime}{\"\n\"}{end}"
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```
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{{% /capture %}}
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