json indent formatter

json-fmt.go

// echo {"a":"b"} | go run json-fmt.go [-prefix ""] [-indent "  "]
// go run json-fmt.go [-prefix ""] [-indent "  "] {\"a\":\"b\"}
// go run json-fmt.go [-prefix ""] [-indent "  "] -file data.json

package main

import (
	"encoding/json"
	"flag"
	. "gist.github.com/9521299.git"
	"io/ioutil"
	"os"
	"strings"
)

func main() {
	var (
		prefix  = flag.String("prefix", "", "prefix string")
		indent  = flag.String("indent", "  ", "indent string")
		file    = flag.String("file", "", "fmt filename")
		bufRead []byte
		errRead error
		data    interface{}
	)
	flag.Parse()

	if *file != "" {
		bufRead, errRead = ioutil.ReadFile(*file)
	} else if flag.NArg() > 0 {
		bufRead = []byte(strings.Join(flag.Args(), " "))
	} else {
		bufRead, errRead = ioutil.ReadAll(os.Stdin)
	}
	Die(errRead, "Read Input")

	err := json.Unmarshal(bufRead, &data)
	Die(err, "Json Unmarshal")
	bufWrite, errMarshal := json.MarshalIndent(data, *prefix, *indent)
	Die(errMarshal, "Json Indent Marshal")

	if *file != "" {
		err := ioutil.WriteFile(*file, bufWrite, os.ModePerm)
		Die(err, "Write Output")
	} else {
		_, err := os.Stdout.Write(bufWrite)
		Die(err, "Write Output")
	}
}