# gojq
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### Pure Go implementation of [jq](https://github.com/jqlang/jq)
This is an implementation of jq command written in Go language.
You can also embed gojq as a library to your Go products.

## Usage
```sh
 $ echo '{"foo": 128}' | gojq '.foo'
128
 $ echo '{"a": {"b": 42}}' | gojq '.a.b'
42
 $ echo '{"id": "sample", "10": {"b": 42}}' | gojq '{(.id): .["10"].b}'
{
  "sample": 42
}
 $ echo '[{"id":1},{"id":2},{"id":3}]' | gojq '.[] | .id'
1
2
3
 $ echo '{"a":1,"b":2}' | gojq '.a += 1 | .b *= 2'
{
  "a": 2,
  "b": 4
}
 $ echo '{"a":1} [2] 3' | gojq '. as {$a} ?// [$a] ?// $a | $a'
1
2
3
 $ echo '{"foo": 4722366482869645213696}' | gojq .foo
4722366482869645213696  # keeps the precision of large numbers
 $ gojq -n 'def fact($n): if $n < 1 then 1 else $n * fact($n - 1) end; fact(50)'
30414093201713378043612608166064768844377641568960512000000000000 # arbitrary-precision integer calculation
```

Nice error messages.
```sh
 $ echo '[1,2,3]' | gojq '.foo & .bar'
gojq: invalid query: .foo & .bar
    .foo & .bar
         ^  unexpected token "&"
 $ echo '{"foo": { bar: [] } }' | gojq '.'
gojq: invalid json: <stdin>
    {"foo": { bar: [] } }
              ^  invalid character 'b' looking for beginning of object key string
```

## Installation
### Homebrew
```sh
brew install gojq
```

### Zero Install
```sh
0install add gojq https://apps.0install.net/utils/gojq.xml
```

### Build from source
```sh
go install github.com/itchyny/gojq/cmd/gojq@latest
```

### Docker
```sh
docker run -i --rm itchyny/gojq
docker run -i --rm ghcr.io/itchyny/gojq
```

## Difference to jq
- gojq is purely implemented with Go language and is completely portable. jq depends on the C standard library so the availability of math functions depends on the library. jq also depends on the regular expression library and it makes build scripts complex.
- gojq implements nice error messages for invalid query and JSON input. The error message of jq is sometimes difficult to tell where to fix the query.
- gojq does not keep the order of object keys. I understand this might cause problems for some scripts but basically, we should not rely on the order of object keys. Due to this limitation, gojq does not have `keys_unsorted` function and `--sort-keys` (`-S`) option. I would implement when ordered map is implemented in the standard library of Go but I'm less motivated.
- gojq supports arbitrary-precision integer calculation while jq does not; jq loses the precision of large integers when calculation is involved. Note that even with gojq, all mathematical functions, including `floor` and `round`, convert integers to floating-point numbers; only addition, subtraction, multiplication, modulo, and division operators (when divisible) keep the integer precision. To calculate floor division of integers without losing the precision, use `def idivide($n): (. - . % $n) / $n;`. To round down floating-point numbers to integers, use `def ifloor: floor | tostring | tonumber;`, but note that this function does not work with large floating-point numbers and also loses the precision of large integers.
- gojq behaves differently than jq in some features, hoping that jq will fix the behaviors in the future. gojq consistently counts by characters (not by bytes) in `index`, `rindex`, and `indices` functions; `"１２３４５" | .[index("３"):]` results in `"３４５"` ([jq#1430](https://github.com/jqlang/jq/issues/1430), [jq#1624](https://github.com/jqlang/jq/issues/1624)). gojq supports string indexing; `"abcde"[2]` ([jq#1520](https://github.com/jqlang/jq/issues/1520)). gojq fixes handling files with no newline characters at the end ([jq#2374](https://github.com/jqlang/jq/issues/2374)). gojq consistently truncates down floating-point number indices both in indexing (`[0] | .[0.5]` results in `0`), and slicing (`[0,1,2] | .[0.5:1.5]` results in `[0]`). gojq parses unary operators with higher precedence than variable binding (`[-1 as $x | 1,$x]` results in `[1,-1]` not `[-1,-1]`) ([jq#3053](https://github.com/jqlang/jq/pull/3053)). gojq fixes `@base64d` to allow binary string as the decoded string ([jq#1931](https://github.com/jqlang/jq/issues/1931)). gojq improves time formatting and parsing; deals with `%f` in `strftime` and `strptime` ([jq#1409](https://github.com/jqlang/jq/issues/1409)), parses timezone offsets with `fromdate` and `fromdateiso8601` ([jq#1053](https://github.com/jqlang/jq/issues/1053)), supports timezone name/offset with `%Z`/`%z` in `strptime` ([jq#929](https://github.com/jqlang/jq/issues/929), [jq#2195](https://github.com/jqlang/jq/issues/2195)), and looks up correct timezone during daylight saving time on formatting with `%Z` ([jq#1912](https://github.com/jqlang/jq/issues/1912)). gojq supports nanoseconds in date and time functions.
- gojq does not support some functions intentionally; `get_jq_origin`, `get_prog_origin`, `get_search_list` (unstable, not listed in jq document), `input_line_number`, `$__loc__` (performance issue). gojq does not support some flags; `--ascii-output, -a` (performance issue), `--seq` (not used commonly), `--sort-keys, -S` (sorts by default because `map[string]any` does not keep the order), `--unbuffered` (unbuffered by default). gojq does not parse JSON extensions supported by jq; `NaN`, `Infinity`, and `[000]`. gojq normalizes floating-point numbers to fit to double-precision floating-point numbers. gojq does not support some regular expression metacharacters, backreferences, look-around assertions, and some flags (regular expression engine differences). gojq does not support BOM (`encoding/json` does not support this). gojq disallows using keywords for function names (`def true: .; true` is a confusing query), and module name prefixes in function declarations (using module prefixes like `def m::f: .;` is undocumented).
- gojq supports reading from YAML input (`--yaml-input`) while jq does not. gojq also supports YAML output (`--yaml-output`). gojq supports `@urid` format string ([jq#798](https://github.com/jqlang/jq/issues/798), [jq#2261](https://github.com/jqlang/jq/issues/2261)).

### Color configuration
The gojq command automatically disables coloring output when the output is not a tty.
To force coloring output, specify `--color-output` (`-C`) option.
When [`NO_COLOR` environment variable](https://no-color.org/) is present or `--monochrome-output` (`-M`) option is specified, gojq disables coloring output.

Use `GOJQ_COLORS` environment variable to configure individual colors.
The variable is a colon-separated list of ANSI escape sequences of `null`, `false`, `true`, numbers, strings, object keys, arrays, and objects.
The default configuration is `90:33:33:36:32:34;1`.

## Usage as a library
You can use the gojq parser and interpreter from your Go products.

```go
package main

import (
	"fmt"
	"log"

	"github.com/itchyny/gojq"
)

func main() {
	query, err := gojq.Parse(".foo | ..")
	if err != nil {
		log.Fatalln(err)
	}
	input := map[string]any{"foo": []any{1, 2, 3}}
	iter := query.Run(input) // or query.RunWithContext
	for {
		v, ok := iter.Next()
		if !ok {
			break
		}
		if err, ok := v.(error); ok {
			if err, ok := err.(*gojq.HaltError); ok && err.Value() == nil {
				break
			}
			log.Fatalln(err)
		}
		fmt.Printf("%#v\n", v)
	}
}
```

- Firstly, use [`gojq.Parse(string) (*Query, error)`](https://pkg.go.dev/github.com/itchyny/gojq#Parse) to get the query from a string.
  - Use [`gojq.ParseError`](https://pkg.go.dev/github.com/itchyny/gojq#ParseError) to get the error position and token of the parsing error.
- Secondly, get the result iterator
  - using [`query.Run`](https://pkg.go.dev/github.com/itchyny/gojq#Query.Run) or [`query.RunWithContext`](https://pkg.go.dev/github.com/itchyny/gojq#Query.RunWithContext)
  - or alternatively, compile the query using [`gojq.Compile`](https://pkg.go.dev/github.com/itchyny/gojq#Compile) and then [`code.Run`](https://pkg.go.dev/github.com/itchyny/gojq#Code.Run) or [`code.RunWithContext`](https://pkg.go.dev/github.com/itchyny/gojq#Code.RunWithContext). You can reuse the `*Code` against multiple inputs to avoid compilation of the same query. But for arguments of `code.Run`, do not give values sharing same data between multiple calls.
  - In either case, you cannot use custom type values as the query input. The type should be `[]any` for an array and `map[string]any` for a map (just like decoded to an `any` using the [encoding/json](https://golang.org/pkg/encoding/json/) package). You can't use `[]int` or `map[string]string`, for example. If you want to query your custom struct, marshal to JSON, unmarshal to `any` and use it as the query input.
- Thirdly, iterate through the results using [`iter.Next() (any, bool)`](https://pkg.go.dev/github.com/itchyny/gojq#Iter). The iterator can emit an error so make sure to handle it. The method returns `true` with results, and `false` when the iterator terminates.
  - The return type is not `(any, error)` because the iterator may emit multiple errors. The `jq` and `gojq` commands stop the iteration on the first error, but the library user can choose to stop the iteration on errors, or to continue until it terminates.
    - In any case, it is recommended to stop the iteration on [`gojq.HaltError`](https://pkg.go.dev/github.com/itchyny/gojq#HaltError), which is emitted by `halt` and `halt_error` functions, although these functions are rarely used.
      The error implements [`gojq.ValueError`](https://pkg.go.dev/github.com/itchyny/gojq#ValueError), and if the error value is `nil`, stop the iteration without handling the error.
      Technically speaking, we can fix the iterator to terminate on the halting error, but it does not terminate at the moment.
      The `halt` function in jq not only stops the iteration, but also terminates the command execution, even if there are still input values.
      So, gojq leaves it up to the library user how to handle the halting error.
  - Note that the result iterator may emit infinite number of values; `repeat(0)` and `range(infinite)`. It may stuck with no output value; `def f: f; f`. Use `RunWithContext` when you want to limit the execution time.

[`gojq.Compile`](https://pkg.go.dev/github.com/itchyny/gojq#Compile) allows to configure the following compiler options.

- [`gojq.WithModuleLoader`](https://pkg.go.dev/github.com/itchyny/gojq#WithModuleLoader) allows to load modules. By default, the module feature is disabled. If you want to load modules from the file system, use [`gojq.NewModuleLoader`](https://pkg.go.dev/github.com/itchyny/gojq#NewModuleLoader).
- [`gojq.WithEnvironLoader`](https://pkg.go.dev/github.com/itchyny/gojq#WithEnvironLoader) allows to configure the environment variables referenced by `env` and `$ENV`. By default, OS environment variables are not accessible due to security reasons. You can use `gojq.WithEnvironLoader(os.Environ)` if you want.
- [`gojq.WithVariables`](https://pkg.go.dev/github.com/itchyny/gojq#WithVariables) allows to configure the variables which can be used in the query. Pass the values of the variables to [`code.Run`](https://pkg.go.dev/github.com/itchyny/gojq#Code.Run) in the same order.
- [`gojq.WithFunction`](https://pkg.go.dev/github.com/itchyny/gojq#WithFunction) allows to add a custom internal function. An internal function can return a single value (which can be an error) each invocation. To add a jq function (which may include a comma operator to emit multiple values, `empty` function, accept a filter for its argument, or call another built-in function), use `LoadInitModules` of the module loader.
- [`gojq.WithIterFunction`](https://pkg.go.dev/github.com/itchyny/gojq#WithIterFunction) allows to add a custom iterator function. An iterator function returns an iterator to emit multiple values. You cannot define both iterator and non-iterator functions of the same name (with possibly different arities). You can use [`gojq.NewIter`](https://pkg.go.dev/github.com/itchyny/gojq#NewIter) to convert values or an error to a [`gojq.Iter`](https://pkg.go.dev/github.com/itchyny/gojq#Iter).
- [`gojq.WithInputIter`](https://pkg.go.dev/github.com/itchyny/gojq#WithInputIter) allows to use `input` and `inputs` functions. By default, these functions are disabled.

## Bug Tracker
Report bug at [Issues・itchyny/gojq - GitHub](https://github.com/itchyny/gojq/issues).

## Author
itchyny (<https://github.com/itchyny>)

## License
This software is released under the MIT License, see LICENSE.
