Pretty print JSON files faster than json_pp

jsonpp.go

// build by running go build ./jsonpp.go
package main

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

func usage() {
	fmt.Println("Usage: jsonpp file.json")
	fmt.Println("       cat file.json | jsonpp")
	fmt.Println("       jsonpp < file.json")
	fmt.Println("\nPretty print JSON files faster than json_pp")
}

func main() {
	var data []byte
	var err error

	stat, _ := os.Stdin.Stat()
	if (stat.Mode() & os.ModeCharDevice) == 0 {
		buf := bytes.NewBuffer([]byte{})
		io.Copy(buf, os.Stdin)
		data = buf.Bytes()
	} else {
		if len(os.Args) != 2 {
			usage()
			os.Exit(1)
		}

		data, err = ioutil.ReadFile(os.Args[1])
		if err != nil {
			panic(err)
		}
	}

	prettyPrint(data)
}

func prettyPrint(b []byte) {
	var buf bytes.Buffer
	if err := json.Indent(&buf, b, "", "  "); err != nil {
		panic(err)
	}

	io.Copy(os.Stdout, bytes.NewReader(buf.Bytes()))
	fmt.Println()
}