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53 lines
1.5 KiB
Markdown
53 lines
1.5 KiB
Markdown
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## Find items in an array
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Given a sample.yml file of:
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```yaml
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- name: Foo
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numBuckets: 0
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- name: Bar
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numBuckets: 0
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```
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then
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```bash
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yq '.[] | select(.name == "Foo")' sample.yml
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```
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will output
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```yaml
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name: Foo
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numBuckets: 0
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```
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### Explanation:
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- `.[]` splats the array, and puts all the items in the context.
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- These items are then piped (`|`) into `select(.name == "Foo")` which will select all the nodes that have a name property set to 'Foo'.
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- See the [select](https://mikefarah.gitbook.io/yq/operators/select) operator for more information.
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## Find and update items in an array
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Given a sample.yml file of:
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```yaml
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- name: Foo
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numBuckets: 0
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- name: Bar
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numBuckets: 0
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```
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then
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```bash
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yq '(.[] | select(.name == "Foo") | .numBuckets) |= . + 1' sample.yml
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```
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will output
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```yaml
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- name: Foo
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numBuckets: 1
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- name: Bar
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numBuckets: 0
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```
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### Explanation:
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- Following from the example above`.[]` splats the array, selects filters the items.
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- We then pipe (`|`) that into `.numBuckets`, which will select that field from all the matching items
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- Splat, select and the field are all in brackets, that whole expression is passed to the `|=` operator as the left hand side expression, with `. + 1` as the right hand side expression.
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- `|=` is the operator that updates fields relative to their own value, which is referenced as dot (`.`).
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- The expression `. + 1` increments the numBuckets counter.
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- See the [assign](https://mikefarah.gitbook.io/yq/operators/assign-update) and [add](https://mikefarah.gitbook.io/yq/operators/add) operators for more information.
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