|  | # 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' |