yq/pkg/yqlib/doc/operators/equals.md

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# Equals / Not Equals
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This is a boolean operator that will return `true` if the LHS is equal to the RHS and `false` otherwise.
```
.a == .b
```
It is most often used with the select operator to find particular nodes:
```
select(.a == .b)
```
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The not equals `!=` operator returns `false` if the LHS is equal to the RHS.
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{% hint style="warning" %}
Note that versions prior to 4.18 require the 'eval/e' command to be specified. 
`yq e <exp> <file>`
{% endhint %}
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## Match string
Given a sample.yml file of:
```yaml
- cat
- goat
- dog
```
then
```bash
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yq '.[] | (. == "*at")' sample.yml
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```
will output
```yaml
true
true
false
```
## Don't match string
Given a sample.yml file of:
```yaml
- cat
- goat
- dog
```
then
```bash
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yq '.[] | (. != "*at")' sample.yml
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```
will output
```yaml
false
false
true
```
## Match number
Given a sample.yml file of:
```yaml
- 3
- 4
- 5
```
then
```bash
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yq '.[] | (. == 4)' sample.yml
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```
will output
```yaml
false
true
false
```
## Dont match number
Given a sample.yml file of:
```yaml
- 3
- 4
- 5
```
then
```bash
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yq '.[] | (. != 4)' sample.yml
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```
will output
```yaml
true
false
true
```
## Match nulls
Running
```bash
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yq --null-input 'null == ~'
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```
will output
```yaml
true
```
## Non exisitant key doesn't equal a value
Given a sample.yml file of:
```yaml
a: frog
```
then
```bash
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yq 'select(.b != "thing")' sample.yml
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```
will output
```yaml
a: frog
```
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## Two non existent keys are equal
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Given a sample.yml file of:
```yaml
a: frog
```
then
```bash
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yq 'select(.b == .c)' sample.yml
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```
will output
```yaml
a: frog
```