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      1 # go-jmespath - A JMESPath implementation in Go
      2 
      3 [![Build Status](https://img.shields.io/travis/jmespath/go-jmespath.svg)](https://travis-ci.org/jmespath/go-jmespath)
      4 
      5 
      6 
      7 go-jmespath is a GO implementation of JMESPath,
      8 which is a query language for JSON.  It will take a JSON
      9 document and transform it into another JSON document
     10 through a JMESPath expression.
     11 
     12 Using go-jmespath is really easy.  There's a single function
     13 you 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)
     23 result = 2
     24 ```
     25 
     26 In the example we gave the ``search`` function input data of
     27 `{"foo": {"bar": {"baz": [0, 1, 2, 3, 4]}}}` as well as the JMESPath
     28 expression `foo.bar.baz[2]`, and the `search` function evaluated
     29 the expression against the input data to produce the result ``2``.
     30 
     31 The JMESPath language can do a lot more than select an element
     32 from 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)
     39 result = { "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)
     47 result [ '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`]")
     56 result = [ { age: 35 }, { age: 40 } ]
     57 ```
     58 
     59 You can also pre-compile your query. This is usefull if 
     60 you 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 
     76 The example above only show a small amount of what
     77 a JMESPath expression can do.  If you want to take a
     78 tour of the language, the *best* place to go is the
     79 [JMESPath Tutorial](http://jmespath.org/tutorial.html).
     80 
     81 One of the best things about JMESPath is that it is
     82 implemented in many different programming languages including
     83 python, ruby, php, lua, etc.  To see a complete list of libraries,
     84 check out the [JMESPath libraries page](http://jmespath.org/libraries.html).
     85 
     86 And finally, the full JMESPath specification can be found
     87 on the [JMESPath site](http://jmespath.org/specification.html).