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yq/usage/value-parsing.md
2020-06-16 01:19:04 +00:00

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---
description: >-
How values are parsed from the CLI to commands that create/update yaml (e.g.
new/write).
---
# Value Parsing
`yq` attempts to parse values intelligently, e.g. when a number is passed it - it will assume it's a number as opposed to a string. `yq` will not alter the representation of what you give. So if you pass '03.0' in, it will assume it's a number and keep the value formatted as it was passed in, that is '03.0'.
The `--tag` flag can be used to override the tag type to force particular tags.
## Default behavior
### Integers
_Given_
```bash
yq new key 3
```
results in
```yaml
key: 3
```
_Given a formatted number_
```bash
yq new key 03
```
results in
```yaml
key: 03
```
`yq` keeps the number formatted as it was passed in.
### Float
_Given_
```bash
yq new key "3.1"
```
results in
```yaml
key: 3.1
```
Note that quoting the number does not make a difference.
_Given a formatted decimal number_
```bash
yq new key 03.0
```
results in
```yaml
key: 03.0
```
`yq` keeps the number formatted as it was passed in
### Booleans
```bash
yq new key true
```
results in
```yaml
key: true
```
### Nulls
```bash
yq new key null
```
results in
```yaml
key: null
```
```bash
yq new key '~'
```
results in
```yaml
key: ~
```
```bash
yq new key ''
```
results in
```yaml
key:
```
### Strings
```bash
yq new key whatever
```
results in
```yaml
key: whatever
```
```bash
yq new key ' whatever '
```
results in
```yaml
key: ' whatever '
```
## Using the tag flag to cast
Previous versions of yq required double quoting to force values to be strings, this no longer works - instead use the --tag flag.
### Casting booleans
```bash
yq new --tag '!!str' key true
```
results in
```yaml
key: "true"
```
### Casting nulls
```bash
yq new --tag '!!str' key null
```
results in
```yaml
key: "null"
```
### Custom types
```bash
yq new --tag '!!farah' key gold
```
results in
```yaml
key: !!farah gold
```
## The style flag
The `--style` flag can be used to specify the quote or block style of the node value. Valid values are
* single
* double
* folded
* flow
* literal
* tagged
For example, given:
```bash
MULTILINE=$(cat <<END
This is line one.
This is line two.
END
)
SINGLE="only one line"
```
### Single
```yaml
yq n --style single things "$MULTILINE"
```
```yaml
things: 'This is line one.
This is line two.'
```
### Double
```yaml
things: "This is line one.\nThis is line two."
```
### Folded:
```yaml
things: >-
This is line one.
This is line two.
```
#### Folded single line:
```yaml
things: >-
only one line
```
### Flow:
```yaml
things: |-
This is line one.
This is line two.
```
#### Flow single line:
```yaml
things: only one line
```
### Literal
```yaml
things: |-
This is line one.
This is line two.
```
#### Literal single line
```yaml
things: |-
only one line
```
### Tagged
Always show the tag, note - you must also pass in `--tag='!!str'`
```yaml
things: !!str |-
This is line one.
This is line two.
```
#### Tagged single line
```yaml
things: !!str only one line
```