yq/operators/select.md
2022-03-29 11:12:22 +11:00

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Markdown

# Select
Select is used to filter arrays and maps by a boolean expression.
## Related Operators
- equals / not equals (`==`, `!=`) operators [here](https://mikefarah.gitbook.io/yq/operators/equals)
- comparison (`>=`, `<` etc) operators [here](https://mikefarah.gitbook.io/yq/operators/compare)
- boolean operators (`and`, `or`, `any` etc) [here](https://mikefarah.gitbook.io/yq/operators/boolean-operators)
{% hint style="warning" %}
Note that versions prior to 4.18 require the 'eval/e' command to be specified.&#x20;
`yq e <exp> <file>`
{% endhint %}
## Select elements from array using wildcard prefix
Given a sample.yml file of:
```yaml
- cat
- goat
- dog
```
then
```bash
yq '.[] | select(. == "*at")' sample.yml
```
will output
```yaml
cat
goat
```
## Select elements from array using wildcard suffix
Given a sample.yml file of:
```yaml
- go-kart
- goat
- dog
```
then
```bash
yq '.[] | select(. == "go*")' sample.yml
```
will output
```yaml
go-kart
goat
```
## Select elements from array using wildcard prefix and suffix
Given a sample.yml file of:
```yaml
- ago
- go
- meow
- going
```
then
```bash
yq '.[] | select(. == "*go*")' sample.yml
```
will output
```yaml
ago
go
going
```
## Select elements from array with regular expression
See more regular expression examples under the `string` operator docs.
Given a sample.yml file of:
```yaml
- this_0
- not_this
- nor_0_this
- thisTo_4
```
then
```bash
yq '.[] | select(test("[a-zA-Z]+_[0-9]$"))' sample.yml
```
will output
```yaml
this_0
thisTo_4
```
## Select items from a map
Given a sample.yml file of:
```yaml
things: cat
bob: goat
horse: dog
```
then
```bash
yq '.[] | select(. == "cat" or test("og$"))' sample.yml
```
will output
```yaml
cat
dog
```
## Use select and with_entries to filter map keys
Given a sample.yml file of:
```yaml
name: bob
legs: 2
game: poker
```
then
```bash
yq 'with_entries(select(.key | test("ame$")))' sample.yml
```
will output
```yaml
name: bob
game: poker
```
## Select multiple items in a map and update
Note the brackets around the entire LHS.
Given a sample.yml file of:
```yaml
a:
things: cat
bob: goat
horse: dog
```
then
```bash
yq '(.a.[] | select(. == "cat" or . == "goat")) |= "rabbit"' sample.yml
```
will output
```yaml
a:
things: rabbit
bob: rabbit
horse: dog
```