#!/usr/bin/python

import os
import sys
import time
from gps import *

print 'Set System Clock to GPS UTC time'

try:
  gpsd = gps(mode=WATCH_ENABLE)
except:
  print 'ERROR: No GPS Present, time not set!!'
  sys.exit()

while True:
  #wait until the next GPSD time tick
  gpsd.next()
  if gpsd.utc != None and gpsd.utc != '':
    #gpsd.utc is formatted like"2015-04-01T17:32:04.000Z"
    #convert it to a form the date -u command will accept: "20140401 17:32:04"
    #use python slice notation [start:end] (where end desired end char + 1)
    #   gpsd.utc[0:4] is "2015"
    #   gpsd.utc[5:7] is "04"
    #   gpsd.utc[8:10] is "01"
    gpsutc = gpsd.utc[0:4] + gpsd.utc[5:7] + gpsd.utc[8:10] + ' ' + gpsd.utc[11:19]
    os.system('sudo date -u --set="%s"' % gpsutc)
    sys.exit()