Command line utility for checking hashes and checksums of files easily. [MIT License]

sig.py

# sig.py -- Basic hash and checksum utility in Python.
# Copyright (c) Philip Conrad, 2015. All rights reserved.
# Released under the MIT License. (http://opensource.org/licenses/MIT)

import hashlib
import sys
import argparse

# Function for incrementally reading text from HUGE files.
def read_file(f, block_size=1024):
    # f is an already open file.
    while True:
        piece = f.read(block_size)
        if piece:
            yield piece
        else:
            return


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Generate hashes for files.')
    parser.add_argument('filenames', type=argparse.FileType('rb'), nargs='+',
                       help='filenames to compute hashes for.')
    # Algorithms that are always available in hashlib:
    # md5(), sha1(), sha224(), sha256(), sha384(), and sha512().
    parser.add_argument("--md5", action="store_true",
                    help="use MD5 hash algorithm")
    parser.add_argument("--sha1", action="store_true",
                    help="use SHA1 hash algorithm")
    parser.add_argument("--sha224", action="store_true",
                    help="use SHA224 hash algorithm")
    parser.add_argument("--sha256", action="store_true",
                    help="use SHA256 hash algorithm")
    parser.add_argument("--sha384", action="store_true",
                    help="use SHA384 hash algorithm")
    parser.add_argument("--sha512", action="store_true",
                    help="use SHA512 hash algorithm")

    # If no args provided, print help and terminate.
    if len(sys.argv[1:]) == 0:
        parser.print_help()
        # parser.print_usage() # for just the usage line
        parser.exit()

    args = parser.parse_args()

    m = None
    algo = ""
    if args.md5:
        m = hashlib.md5()
    elif args.sha1:
        m = hashlib.sha1()
    elif args.sha224:
        m = hashlib.sha224()
    elif args.sha256:
        m = hashlib.sha256()
    elif args.sha384:
        m = hashlib.sha384()
    elif args.sha512:
        m = hashlib.sha512()
    else:
        parser.print_help()
        parser.exit()

    # 'm' should always be initialized by this point.
    for f in args.filenames:
        h = m.copy()                # Copy the current hash algorithm.
        for chunk in read_file(f):  # Get the plaintext to be hashed.
            h.update(chunk)         # Run text through the hash algorithm.
        print f.name + " :: " + h.hexdigest()  # Print out results.