yq/pkg/yqlib/doc/usage/properties.md
2022-02-06 14:39:46 +11:00

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# Properties
Encode to a property file (decode not yet supported). Line comments on value nodes will be copied across.
By default, empty maps and arrays are not encoded - see below for an example on how to encode a value for these.
{% hint style="warning" %}
Note that versions prior to 4.18 require the 'eval/e' command to be specified. 
`yq e <exp> <file>`
{% endhint %}
## Encode properties
Note that empty arrays and maps are not encoded by default.
Given a sample.yml file of:
```yaml
# block comments don't come through
person: # neither do comments on maps
name: Mike # comments on values appear
pets:
- cat # comments on array values appear
food: [pizza] # comments on arrays do not
emptyArray: []
emptyMap: []
```
then
```bash
yq -o=props -I=0 '.' sample.yml
```
will output
```properties
# comments on values appear
person.name = Mike
# comments on array values appear
person.pets.0 = cat
person.food.0 = pizza
```
## Encode properties: no comments
Given a sample.yml file of:
```yaml
# block comments don't come through
person: # neither do comments on maps
name: Mike # comments on values appear
pets:
- cat # comments on array values appear
food: [pizza] # comments on arrays do not
emptyArray: []
emptyMap: []
```
then
```bash
yq -o=props -I=0 '... comments = ""' sample.yml
```
will output
```properties
person.name = Mike
person.pets.0 = cat
person.food.0 = pizza
```
## Encode properties: include empty maps and arrays
Use a yq expression to set the empty maps and sequences to your desired value.
Given a sample.yml file of:
```yaml
# block comments don't come through
person: # neither do comments on maps
name: Mike # comments on values appear
pets:
- cat # comments on array values appear
food: [pizza] # comments on arrays do not
emptyArray: []
emptyMap: []
```
then
```bash
yq -o=props -I=0 '(.. | select( (tag == "!!map" or tag =="!!seq") and length == 0)) = ""' sample.yml
```
will output
```properties
# comments on values appear
person.name = Mike
# comments on array values appear
person.pets.0 = cat
person.food.0 = pizza
emptyArray =
emptyMap =
```