diff -r be3874cf87f3 Doc/library/hashlib.rst
--- a/Doc/library/hashlib.rst	Sat Mar 05 14:05:45 2016 +0200
+++ b/Doc/library/hashlib.rst	Sat Mar 05 23:43:36 2016 +0200
@@ -176,6 +176,35 @@
    compute the digests of data sharing a common initial substring.
 
 
+.. _hashlib-commandline:
+
+Command Line Interface
+----------------------
+
+.. versionadded:: 3.6
+
+:mod:`hashlib` can also be invoked directly using the :option:`-m`
+switch of the interpreter with a ``algorithm`` argument.
+
+When a ``file`` argument is given the hash is calculated on the file::
+
+    $ python -m hashlib md5 /bin/sh
+    $ d985d0ea551c1253c2305140c583d11f
+
+With no ``file``, or when ``file`` is -, read standard input::
+
+    $ cat /bin/sh | python -m hashlib md5
+    $ d985d0ea551c1253c2305140c583d11f
+
+By default, we read up to 1024 bytes at a time from the given file.
+The option :option:`-b` can be used to change the reading block size.
+For example, the following command causes the the file to be read up
+to 512 bytes at a time::
+
+    $ python -m hashlib -b 512 sha1 /bin/sh
+    $ 647437c3d7543c7c8d381903834c9ef42eb4cf69
+
+
 Key derivation
 --------------
 
diff -r be3874cf87f3 Lib/hashlib.py
--- a/Lib/hashlib.py	Sat Mar 05 14:05:45 2016 +0200
+++ b/Lib/hashlib.py	Sat Mar 05 23:43:36 2016 +0200
@@ -1,3 +1,4 @@
+#! /usr/bin/env python3
 #.  Copyright (C) 2005-2010   Gregory P. Smith (greg@krypto.org)
 #  Licensed to PSF under a Contributor Agreement.
 #
@@ -215,3 +216,31 @@
 # Cleanup locals()
 del __always_supported, __func_name, __get_hash
 del __py_new, __hash_new, __get_openssl_constructor
+
+
+# Usable as a script...
+def main():
+    import argparse
+    import sys
+    parser = argparse.ArgumentParser()
+    parser.add_argument('-b', metavar='BLOCK_SIZE', type=int,
+                        dest="block_size", default=2**10,
+                        help='Read up to BLOCK_SIZE bytes at a time.')
+    parser.add_argument('algorithm', action='store', type=str,
+                        choices=('md5', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512'),
+                        help='Specify algorithm to use for hash calculation.')
+    parser.add_argument('file', metavar='FILE', type=argparse.FileType("rb"),
+                        default=sys.stdin.buffer, nargs='?',
+                        help='Calculate hash on given file. With no FILE, or when FILE is -, read standard input.')
+    args = parser.parse_args()
+    hash_obj = globals()[args.algorithm]()
+    while True:
+        data = args.file.read(args.block_size)
+        if not data:
+            break
+        hash_obj.update(data)
+    print(hash_obj.hexdigest())
+
+
+if __name__ == '__main__':
+    main()
diff -r be3874cf87f3 Lib/test/test_hashlib.py
--- a/Lib/test/test_hashlib.py	Sat Mar 05 14:05:45 2016 +0200
+++ b/Lib/test/test_hashlib.py	Sat Mar 05 23:43:36 2016 +0200
@@ -18,7 +18,7 @@
 import unittest
 import warnings
 from test import support
-from test.support import _4G, bigmemtest, import_fresh_module
+from test.support import _4G, bigmemtest, import_fresh_module, script_helper
 
 # Were we compiled --with-pydebug or with #define Py_DEBUG?
 COMPILED_WITH_PYDEBUG = hasattr(sys, 'gettotalrefcount')
@@ -526,5 +526,41 @@
         self._test_pbkdf2_hmac(c_hashlib.pbkdf2_hmac)
 
 
+class TestMain(unittest.TestCase):
+    supported_algorithms = ('md5', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512')
+    data = b"abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"
+
+    def setUp(self):
+        with open(support.TESTFN, 'wb') as fp:
+            fp.write(self.data)
+
+    def tearDown(self):
+        if os.path.exists(support.TESTFN):
+            os.unlink(support.TESTFN)
+
+    def get_output(self, *args):
+        return script_helper.assert_python_ok('-m', 'hashlib', *args).out
+
+    def test_calculate_file_hash(self):
+        for algorithm in self.supported_algorithms:
+            output = self.get_output(algorithm, support.TESTFN)
+            calculated = getattr(hashlib, algorithm)(self.data).hexdigest().encode("ascii")
+            self.assertEqual(output.rstrip(), calculated)
+
+    def test_calculate_hash_from_stdin(self):
+        for algorithm in self.supported_algorithms:
+            with script_helper.spawn_python('-m', 'hashlib', algorithm) as proc:
+                out, err = proc.communicate(self.data)
+            calculated = getattr(hashlib, algorithm)(self.data).hexdigest().encode("ascii")
+            self.assertEqual(out.rstrip(), calculated)
+            self.assertIsNone(err)
+
+    def test_block_size(self):
+        for block_size in [2, 2**2, 2**4, 2**8]:
+            output = self.get_output("-b", str(block_size), "md5", support.TESTFN)
+            calculated = getattr(hashlib, "md5")(self.data).hexdigest().encode("ascii")
+            self.assertEqual(output.rstrip(), calculated)
+
+
 if __name__ == "__main__":
     unittest.main()