How can I pretty-print JSON using Go?

Question

Does anyone know of a simple way to pretty-print JSON output in Go?

The stock http://golang.org/pkg/encoding/json/ package does not seem to include functiona

Answer 1

A simple off the shelf pretty printer in Go. One can compile it to a binary through:

go build -o jsonformat jsonformat.go

It reads from standard input, writes to standard output and allow to set indentation:

package main

import (
    "bytes"
    "encoding/json"
    "flag"
    "fmt"
    "io/ioutil"
    "os"
)

func main() {
    indent := flag.String("indent", "  ", "indentation string/character for formatter")
    flag.Parse()
    src, err := ioutil.ReadAll(os.Stdin)
    if err != nil {
        fmt.Fprintf(os.Stderr, "problem reading: %s", err)
        os.Exit(1)
    }

    dst := &bytes.Buffer{}
    if err := json.Indent(dst, src, "", *indent); err != nil {
        fmt.Fprintf(os.Stderr, "problem formatting: %s", err)
        os.Exit(1)
    }
    if _, err = dst.WriteTo(os.Stdout); err != nil {
        fmt.Fprintf(os.Stderr, "problem writing: %s", err)
        os.Exit(1)
    }
}

It allows to run a bash commands like:

cat myfile | jsonformat | grep "key"