root/watcher/trunk/reader.py

import sys
import re
import time
import datetime

pattern = re.compile(r"^GPS Location:\s+(\S+)\s+\S\s+(\S+)"
                     r"\s+\S\s+\S+\s+(\S+)\s+")
bad_coordinate = "69696969.000"
bad_freshness = "1e+308"
stale = 900.0  # position must not be older than this many seconds
timeout = datetime.timedelta(0,300)  # wait up to this many seconds fo log to be appended

glider = sys.argv[1]
log    = sys.argv[2]

handle = open(log)

content = []
timer = datetime.datetime.now()
while True:
    line = handle.readline()
    if line:
        timer = datetime.datetime.now()
        content.append(line)
        match = pattern.search(line)
        if match:
            lat, lon, fresh = match.groups()
            if lat == bad_coordinate:
                continue
            if lon == bad_coordinate:
                continue
            if fresh == bad_freshness:
                continue
            if float(fresh) >= stale:
                print "\nStale GPS fix for %s: %.2f seconds old in %s." % (glider, float(fresh), log),
                sys.stdout.flush()
                continue
            print "\nFresh GPS fix for %s: %.3f %.3f." % (glider, float(lat), float(lon)),
            sys.stdout.flush()
            break
    else:
        if datetime.datetime.now() - timer > timeout:
            print "\nTimeout reading %s log %s." % (glider, log)
            break
        time.sleep(5)

handle.close()