| # Copyright 2013 The Chromium Authors | 
 | # Use of this source code is governed by a BSD-style license that can be | 
 | # found in the LICENSE file. | 
 |  | 
 |  | 
 | import sys | 
 |  | 
 |  | 
 | def IsWindows(): | 
 |   return sys.platform in ['win32', 'cygwin'] | 
 |  | 
 |  | 
 | def IsLinux(): | 
 |   return sys.platform.startswith(('linux', 'freebsd', 'netbsd', 'openbsd')) | 
 |  | 
 |  | 
 | def IsMac(): | 
 |   return sys.platform == 'darwin' | 
 |  | 
 |  | 
 | def host_os(): | 
 |   """ | 
 |   Returns a string representing the host_os of the current system. | 
 |   Possible values: 'win', 'mac', 'linux', 'unknown'. | 
 |   """ | 
 |   if IsWindows(): | 
 |     return 'win' | 
 |   elif IsLinux(): | 
 |     return 'linux' | 
 |   elif IsMac(): | 
 |     return 'mac' | 
 |   else: | 
 |     return 'unknown' |