File Checksums in Go

hash_file.go

// ./hash_file.go sha256 /path/to/file
package main

import (
	"crypto/md5"
	"crypto/sha1"
	"crypto/sha256"
	"fmt"
	"io"
	"log"
	"os"
)

func main() {
	// Open / Read the file to memory
	if len(os.Args) == 3 {
		file, err := os.Open(os.Args[2])
		if err != nil {
			log.Fatal(err)
		}
		defer file.Close()

		// Check os.Args[1] for the hashing algorithm
		if os.Args[1] == "sha256" {
			hash := sha256.New()
			if _, err := io.Copy(hash, file); err != nil {
				log.Fatal(err)
			}
			fmt.Printf("%x  %v\n", hash.Sum(nil), os.Args[2])
		} else if os.Args[1] == "sha1" {
			hash := sha1.New()
			if _, err := io.Copy(hash, file); err != nil {
				log.Fatal(err)
			}
			fmt.Printf("%x  %v\n", hash.Sum(nil), os.Args[2])
		} else if os.Args[1] == "md5" {
			hash := md5.New()
			if _, err := io.Copy(hash, file); err != nil {
				log.Fatal(err)
			}
			fmt.Printf("%x  %v\n", hash.Sum(nil), os.Args[2])
		} else {
			// If first arg doesn't match.
			fmt.Printf("Requires Hashing Algorithm\n./hashfile sha1 /path/to/file\n")
		}
	} else {
		fmt.Printf("Requires File Location\n./hashfile sha1 /path/to/file\n")
	}
}