1# YAML support for the Go language
2
3Introduction
4------------
5
6The yaml package enables Go programs to comfortably encode and decode YAML
7values. It was developed within [Canonical](https://www.canonical.com) as
8part of the [juju](https://juju.ubuntu.com) project, and is based on a
9pure Go port of the well-known [libyaml](http://pyyaml.org/wiki/LibYAML)
10C library to parse and generate YAML data quickly and reliably.
11
12Compatibility
13-------------
14
15The yaml package supports most of YAML 1.1 and 1.2, including support for
16anchors, tags, map merging, etc. Multi-document unmarshalling is not yet
17implemented, and base-60 floats from YAML 1.1 are purposefully not
18supported since they're a poor design and are gone in YAML 1.2.
19
20Installation and usage
21----------------------
22
23The import path for the package is *gopkg.in/yaml.v2*.
24
25To install it, run:
26
27 go get gopkg.in/yaml.v2
28
29API documentation
30-----------------
31
32If opened in a browser, the import path itself leads to the API documentation:
33
34 * [https://gopkg.in/yaml.v2](https://gopkg.in/yaml.v2)
35
36API stability
37-------------
38
39The package API for yaml v2 will remain stable as described in [gopkg.in](https://gopkg.in).
40
41
42License
43-------
44
45The yaml package is licensed under the Apache License 2.0. Please see the LICENSE file for details.
46
47
48Example
49-------
50
51```Go
52package main
53
54import (
55 "fmt"
56 "log"
57
58 "gopkg.in/yaml.v2"
59)
60
61var data = `
62a: Easy!
63b:
64 c: 2
65 d: [3, 4]
66`
67
68// Note: struct fields must be public in order for unmarshal to
69// correctly populate the data.
70type T struct {
71 A string
72 B struct {
73 RenamedC int `yaml:"c"`
74 D []int `yaml:",flow"`
75 }
76}
77
78func main() {
79 t := T{}
80
81 err := yaml.Unmarshal([]byte(data), &t)
82 if err != nil {
83 log.Fatalf("error: %v", err)
84 }
85 fmt.Printf("--- t:\n%v\n\n", t)
86
87 d, err := yaml.Marshal(&t)
88 if err != nil {
89 log.Fatalf("error: %v", err)
90 }
91 fmt.Printf("--- t dump:\n%s\n\n", string(d))
92
93 m := make(map[interface{}]interface{})
94
95 err = yaml.Unmarshal([]byte(data), &m)
96 if err != nil {
97 log.Fatalf("error: %v", err)
98 }
99 fmt.Printf("--- m:\n%v\n\n", m)
100
101 d, err = yaml.Marshal(&m)
102 if err != nil {
103 log.Fatalf("error: %v", err)
104 }
105 fmt.Printf("--- m dump:\n%s\n\n", string(d))
106}
107```
108
109This example will generate the following output:
110
111```
112--- t:
113{Easy! {2 [3 4]}}
114
115--- t dump:
116a: Easy!
117b:
118 c: 2
119 d: [3, 4]
120
121
122--- m:
123map[a:Easy! b:map[c:2 d:[3 4]]]
124
125--- m dump:
126a: Easy!
127b:
128 c: 2
129 d:
130 - 3
131 - 4
132```
133