sha1sum.go

package main

import (
	"crypto/sha1"
	"fmt"
	"io"
	"log"
	"os"
)

func main() {
	if len(os.Args) < 2 {
		log.Fatal("./sha1sum [filename]")
	}
	
	h := sha1.New()

	for _, name := range os.Args[1:] {
		h.Reset()
		
		f, err := os.Open(name)
		if err != nil {
			log.Fatal(err)
		}

		if _, err := io.Copy(h, f); err != nil {
			f.Close()
			log.Fatal(err)
		}

		f.Close()
		fmt.Printf("%x\t%s\n", h.Sum(nil), name)
	}
}