GoLang. Checks the hash of a file against an expected hash.

check-hash.go

package main

import (
	"crypto/md5"
	"crypto/sha256"
	"encoding/hex"
	"flag"
	"fmt"
	"hash"
	"io"
	"log"
	"os"
	"strings"
)

func main() {
	// Parse command-line arguments
	filename := flag.String("filename", "", "Name of the file to check")
	algorithm := flag.String("algorithm", "", "Hashing algorithm (sha256 or md5)")
	expectedHash := flag.String("expected", "", "Expected hash value")
	flag.Parse()

	// Validate command-line arguments
	if *filename == "" || *algorithm == "" || *expectedHash == "" {
		flag.Usage()
		os.Exit(1)
	}

	// Open the file
	file, err := os.Open(*filename)
	if err != nil {
		log.Fatal(err)
	}
	defer file.Close()

	// Create hasher
	var hasher hash.Hash

	// Normalize and validate command line argument -algorithm
	switch strings.ToLower(*algorithm) {
	case "sha256":
		hasher = sha256.New()
	case "md5":
		hasher = md5.New()
	default:
		log.Fatalf("Unsupported algorithm: %s", *algorithm)
	}

	// Copy the contents of the file into the hasher 
	if _, err := io.Copy(hasher, file); err != nil {
		log.Fatal(err)
	}

	// Get the computed hash of the file
	computedHash := hex.EncodeToString(hasher.Sum(nil))

	// Compare the computed hash of the file to the expected hash
	if computedHash == *expectedHash {
		fmt.Println("Hashes match!")
	} else {
		fmt.Println("Hashes do not match!")
		fmt.Printf("Expected: %s\n", *expectedHash)
		fmt.Printf("Computed: %s\n", computedHash)
	}
}