# 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)

## 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](https://mikefarah.gitbook.io/yq/operators/string-operators).

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
```


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