go md5/sha1 example

demo

$ for a in md5 sha1 ; do ./hash -$a /bin/ls; ${a}sum /bin/ls; echo; done
a3f812b9fe329322a3d6b00722694e84  /bin/ls
a3f812b9fe329322a3d6b00722694e84  /bin/ls

9eb997f16adb828cd0273f24b0ae94d32c5a3b3f  /bin/ls
9eb997f16adb828cd0273f24b0ae94d32c5a3b3f  /bin/ls

hash.go

/*
 Hash - Guillermo Estrada

  Simple utility to obtain the MD5 and/or SHA-1 
  of a file from the command line.

  2011
*/

package main

import (
	"io"
	"os"
	"fmt"
	"flag"
	"crypto/md5"
	"crypto/sha1"
)

func main() {

	md5f := flag.Bool("md5", false, "-md5 calculate md5 hash of file")
	sha1f := flag.Bool("sha1", false, "-sha1 calculate sha1 hash of file")
	flag.Parse()
	
	if !*md5f && !*sha1f {
		fmt.Println("err: No hash specified. Use -md5 or -sha1 or both.")
		os.Exit(1)
	}
	
	

	infile, inerr := os.Open(flag.Arg(0))
	if inerr == nil {
		if *md5f {  
			md5h := md5.New()
			io.Copy(md5h,infile)
			fmt.Printf("%x  %s\n",md5h.Sum(), flag.Arg(0))
		}
		if *sha1f {  
			sha1h := sha1.New()
			io.Copy(sha1h,infile)
			fmt.Printf("%x  %s\n",sha1h.Sum(), flag.Arg(0))
		}
		
	} else {
		fmt.Println(inerr)
		os.Exit(1)
	}
}