# YAML support for the Go language
Introduction
------------
The yaml package enables Go programs to comfortably encode and decode YAML
values. It was developed within [Canonical](https://www.canonical.com) as
part of the [juju](https://juju.ubuntu.com) project, and is based on a
pure Go port of the well-known [libyaml](http://pyyaml.org/wiki/LibYAML)
C library to parse and generate YAML data quickly and reliably.
Compatibility
-------------
The yaml package supports most of YAML 1.2, but preserves some behavior
from 1.1 for backwards compatibility.
Specifically, as of v3 of the yaml package:
- YAML 1.1 bools (_yes/no, on/off_) are supported as long as they are being
decoded into a typed bool value. Otherwise they behave as a string. Booleans
in YAML 1.2 are _true/false_ only.
- Octals encode and decode as _0777_ per YAML 1.1, rather than _0o777_
as specified in YAML 1.2, because most parsers still use the old format.
Octals in the _0o777_ format are supported though, so new files work.
- Does not support base-60 floats. These are gone from YAML 1.2, and were
actually never supported by this package as it's clearly a poor choice.
and offers backwards
compatibility with YAML 1.1 in some cases.
1.2, including support for
anchors, tags, map merging, etc. Multi-document unmarshalling is not yet
implemented, and base-60 floats from YAML 1.1 are purposefully not
supported since they're a poor design and are gone in YAML 1.2.
Installation and usage
----------------------
The import path for the package is *gopkg.in/yaml.v3*.
To install it, run:
go get gopkg.in/yaml.v3
API documentation
-----------------
If opened in a browser, the import path itself leads to the API documentation:
- [https://gopkg.in/yaml.v3](https://gopkg.in/yaml.v3)
API stability
-------------
The package API for yaml v3 will remain stable as described in [gopkg.in](https://gopkg.in).
License
-------
The yaml package is licensed under the MIT and Apache License 2.0 licenses.
Please see the LICENSE file for details.
Example
-------
```Go
package main
import (
"fmt"
"log"
"gopkg.in/yaml.v3"
)
var data = `
a: Easy!
b:
c: 2
d: [3, 4]
`
// Note: struct fields must be public in order for unmarshal to
// correctly populate the data.
type T struct {
A string
B struct {
RenamedC int `yaml:"c"`
D []int `yaml:",flow"`
}
}
func main() {
t := T{}
err := yaml.Unmarshal([]byte(data), &t)
if err != nil {
log.Fatalf("error: %v", err)
}
fmt.Printf("--- t:\n%v\n\n", t)
d, err := yaml.Marshal(&t)
if err != nil {
log.Fatalf("error: %v", err)
}
fmt.Printf("--- t dump:\n%s\n\n", string(d))
m := make(map[interface{}]interface{})
err = yaml.Unmarshal([]byte(data), &m)
if err != nil {
log.Fatalf("error: %v", err)
}
fmt.Printf("--- m:\n%v\n\n", m)
d, err = yaml.Marshal(&m)
if err != nil {
log.Fatalf("error: %v", err)
}
fmt.Printf("--- m dump:\n%s\n\n", string(d))
}
```
This example will generate the following output:
```
--- t:
{Easy! {2 [3 4]}}
--- t dump:
a: Easy!
b:
c: 2
d: [3, 4]
--- m:
map[a:Easy! b:map[c:2 d:[3 4]]]
--- m dump:
a: Easy!
b:
c: 2
d:
- 3
- 4
```
