new_contents: ##############################################################################
  # Copyright (c) 2013-2014, Lawrence Livermore National Security, LLC.
  # Produced at the Lawrence Livermore National Laboratory.
  #
  # This file is part of Spack.
  # Written by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
  # LLNL-CODE-647188
  #
  # For details, see https://scalability-llnl.github.io/spack
  # Please also see the LICENSE file for our notice and the LGPL.
  #
  # This program is free software; you can redistribute it and/or modify
  # it under the terms of the GNU General Public License (as published by
  # the Free Software Foundation) version 2.1 dated February 1999.
  #
  # This program is distributed in the hope that it will be useful, but
  # WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
  # conditions of the GNU General Public License for more details.
  #
  # You should have received a copy of the GNU Lesser General Public License
  # along with this program; if not, write to the Free Software Foundation,
  # Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  ##############################################################################
  import os
  import hashlib
  from external import argparse
  
  import llnl.util.tty as tty
  from llnl.util.filesystem import *
  
  import spack.util.crypto
  
  description = "Calculate md5 checksums for files."
  
  def setup_parser(subparser):
      setup_parser.parser = subparser
      subparser.add_argument('files', nargs=argparse.REMAINDER,
                             help="Files to checksum.")
  
  def md5(parser, args):
      if not args.files:
          setup_parser.parser.print_help()
  
      for f in args.files:
          if not os.path.isfile(f):
              tty.die("Not a file: %s" % f)
          if not can_access(f):
              tty.die("Cannot read file: %s" % f)
  
          checksum = spack.util.crypto.checksum(hashlib.md5, f)
          print "%s  %s" % (checksum, f)
  
subject: Add spack md5 command for simple checksumming.