1# go-jmespath - A JMESPath implementation in Go
2
3[](https://travis-ci.org/jmespath/go-jmespath)
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7go-jmespath is a GO implementation of JMESPath,
8which is a query language for JSON. It will take a JSON
9document and transform it into another JSON document
10through a JMESPath expression.
11
12Using go-jmespath is really easy. There's a single function
13you use, `jmespath.search`:
14
15
16```go
17> import "github.com/jmespath/go-jmespath"
18>
19> var jsondata = []byte(`{"foo": {"bar": {"baz": [0, 1, 2, 3, 4]}}}`) // your data
20> var data interface{}
21> err := json.Unmarshal(jsondata, &data)
22> result, err := jmespath.Search("foo.bar.baz[2]", data)
23result = 2
24```
25
26In the example we gave the ``search`` function input data of
27`{"foo": {"bar": {"baz": [0, 1, 2, 3, 4]}}}` as well as the JMESPath
28expression `foo.bar.baz[2]`, and the `search` function evaluated
29the expression against the input data to produce the result ``2``.
30
31The JMESPath language can do a lot more than select an element
32from a list. Here are a few more examples:
33
34```go
35> var jsondata = []byte(`{"foo": {"bar": {"baz": [0, 1, 2, 3, 4]}}}`) // your data
36> var data interface{}
37> err := json.Unmarshal(jsondata, &data)
38> result, err := jmespath.search("foo.bar", data)
39result = { "baz": [ 0, 1, 2, 3, 4 ] }
40
41
42> var jsondata = []byte(`{"foo": [{"first": "a", "last": "b"},
43 {"first": "c", "last": "d"}]}`) // your data
44> var data interface{}
45> err := json.Unmarshal(jsondata, &data)
46> result, err := jmespath.search({"foo[*].first", data)
47result [ 'a', 'c' ]
48
49
50> var jsondata = []byte(`{"foo": [{"age": 20}, {"age": 25},
51 {"age": 30}, {"age": 35},
52 {"age": 40}]}`) // your data
53> var data interface{}
54> err := json.Unmarshal(jsondata, &data)
55> result, err := jmespath.search("foo[?age > `30`]")
56result = [ { age: 35 }, { age: 40 } ]
57```
58
59You can also pre-compile your query. This is usefull if
60you are going to run multiple searches with it:
61
62```go
63 > var jsondata = []byte(`{"foo": "bar"}`)
64 > var data interface{}
65 > err := json.Unmarshal(jsondata, &data)
66 > precompiled, err := Compile("foo")
67 > if err != nil{
68 > // ... handle the error
69 > }
70 > result, err := precompiled.Search(data)
71 result = "bar"
72```
73
74## More Resources
75
76The example above only show a small amount of what
77a JMESPath expression can do. If you want to take a
78tour of the language, the *best* place to go is the
79[JMESPath Tutorial](http://jmespath.org/tutorial.html).
80
81One of the best things about JMESPath is that it is
82implemented in many different programming languages including
83python, ruby, php, lua, etc. To see a complete list of libraries,
84check out the [JMESPath libraries page](http://jmespath.org/libraries.html).
85
86And finally, the full JMESPath specification can be found
87on the [JMESPath site](http://jmespath.org/specification.html).
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