Measure how long any command takes on Windows

subtract_time.py

# Copyright (c) 2017 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""
This script converts two %time% compatible strings passed to it into seconds,
subtracts them, and prints the difference. That's it. It's used by timeit.bat.
"""

from __future__ import print_function

import re
import sys

def ParseTime(time_string):
  # Time looks like 15:19:30.32 or 15:19:30,32 depending on locale
  # (and there might be other variants as well)
  match = re.match("(.*):(.*):(.*)[\.,](.*)", time_string)
  hours, minutes, seconds, fraction = map(int, match.groups())
  return hours * 3600 + minutes * 60 + seconds + fraction * .01


print("%1.2f seconds elapsed time" %
      (ParseTime(sys.argv[1]) - ParseTime(sys.argv[2])))

timeit.bat

@ECHO off

REM Copyright (c) 2017 The Chromium Authors. All rights reserved.
REM Use of this source code is governed by a BSD-style license that can be
REM found in the LICENSE file.

REM This batch file executes the commands passed to it and prints out the
REM elapsed run time.

SETLOCAL
SET starttime=%time%
CALL %*
CALL python %~dp0subtract_time.py %time% %starttime%