package main

import "fmt"
import "os"
import "log"
import "io"

var err error
var from, to *os.File

const bufSize = 64 * 1024

func copyFile(src io.Reader, dst io.Writer) error {
	buf := make([]byte, bufSize)
	for {
		n, er := src.Read(buf)
		if er != nil || n == 0 {
			if er != nil && er != io.EOF {
				return fmt.Errorf("Read error: %v:", er)
			}
			break
		}
		_, wer := dst.Write(buf[:n])
		if wer != nil {
			return fmt.Errorf("Write error: %v:", wer)
		}
	}
	return nil
}

func main() {
	if len(os.Args) != 3 {
		log.Fatalln("Usage: go-cp from to")
	}
	from, err = os.Open(os.Args[1])
	if err != nil {
		log.Fatalln("Error open", err)
	}
	defer from.Close()

	to, err = os.Create(os.Args[2])
	if err != nil {
		log.Fatalln("Error open", err)
	}
	defer to.Close()
	// err = copyFile(from, to)
	_, err = io.Copy(from, to)
	if err != nil {
		log.Fatalln(err)
	}
}