#!/usr/bin/env python
     #
     # Copyright 2007 Doug Hellmann.
     #
     #
     #                         All Rights Reserved
     #
     # Permission to use, copy, modify, and distribute this software and
     # its documentation for any purpose and without fee is hereby
     # granted, provided that the above copyright notice appear in all
     # copies and that both that copyright notice and this permission
     # notice appear in supporting documentation, and that the name of Doug
     # Hellmann not be used in advertising or publicity pertaining to
     # distribution of the software without specific, written prior
     # permission.
     #
     # DOUG HELLMANN DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
     # INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
     # NO EVENT SHALL DOUG HELLMANN BE LIABLE FOR ANY SPECIAL, INDIRECT OR
     # CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
     # OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
     # NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
     # CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     #
     
     """Change permissions on a file
     
     """
     
     __module_id__ = "$Id$"
     #end_pymotw_header
     
     import os
     import stat
     
     filename = 'os_stat_chmod_example.txt'
     if os.path.exists(filename):
         os.unlink(filename)
     f = open(filename, 'wt')
     f.write('contents')
     f.close()
     
     # Determine what permissions are already set using stat
     existing_permissions = stat.S_IMODE(os.stat(filename).st_mode)
     
     if not os.access(filename, os.X_OK):
         print 'Adding execute permission'
         new_permissions = existing_permissions | stat.S_IXUSR
     else:
         print 'Removing execute permission'
         # use xor to remove the user execute permission
         new_permissions = existing_permissions ^ stat.S_IXUSR
     
     os.chmod(filename, new_permissions)