Tiny command line tool to encode IDN domains from stdin to ASCII using IDNA2008. Errors are printed to stderr. ASCII results are printed to stdout.

idna-encode.go

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"strings"

	"golang.org/x/net/idna"
)

func main() {
	stdinBytes, err := ioutil.ReadAll(os.Stdin)
	if err != nil {
		log.Fatalf("Error reading names from standard in: %v\n", err)
	}
	for _, name := range strings.Split(string(stdinBytes), "\n") {
		if name == "" {
			continue
		}
		out, err := idna.ToASCII(name)
		if err != nil {
			fmt.Fprintf(os.Stderr, "error converting %q to ascii: %v\n", name, err)
			continue
		}
		fmt.Printf("%s\n", out)
	}
}