rungps.sh

#!/bin/bash
BASEDIR="/mnt/usbstick"
DATE=$(date +"%Y-%m-%d_%H-%M-%S")
LOGFILE=$BASEDIR/gpslog.txt
RAWFILE=$BASEDIR/gpsdata/gpsraw-$DATE.txt
DATAFILE=$BASEDIR/gpsdata-$DATE.txt
ts=$(date +"%Y/%m/%d %H:%M:%S.%N")
echo $ts "Start GPS Process" >> $LOGFILE
while [ 1 ]
do
    read this_line

    # if cr/lf bothers you, make it lf only
    # (os-specfic concern)
    #
    this_line=$( echo $this_line | sed s/$'\r'//g )

    # get a precise time stamp
    # %N = nanoseconds
    #
    ts=$(date +"%Y/%m/%d %H:%M:%S.%N")

    echo $ts $this_line >> $RAWFILE

    # let us filter the current position
    #
	if [[ $this_line == \$GPGGA* ]]
	then
		gps_time=$(echo $this_line | cut -d, -f 2)
		gps_latdeg=$(echo $this_line | cut -d, -f 3)
		gps_latdir=$(echo $this_line | cut -d, -f 4)
		gps_londeg=$(echo $this_line | cut -d, -f 5)
		gps_londir=$(echo $this_line | cut -d, -f 6)
		gps_fix=$(echo $this_line | cut -d, -f 7)
		gps_sats=$(echo $this_line | cut -d, -f 8)
		gps_hdop=$(echo $this_line | cut -d, -f 9)
		gps_elev=$(echo $this_line | cut -d, -f 10)
		echo $this_line >> $DATAFILE
		sleep 5s
	fi

	if [[ $this_line == \$GPRMC* ]]
	then
        # ok, it looks like a GPS reading (may be void)
        # if field 3 is V, the reading is void (or maybe
        # only untrusted?), if it is A, then the position
        # is Active (and therefore given with confidence?)
        #
		if [[ $(echo $this_line | cut -d, -f 4-6) != ",,," ]]
		then
		# get latitude and longitude
			gps_fix=$(echo $this_line | cut -d, -f 3)
			gps_pos=($(echo $this_line | cut -d, -f 3-7 | tr , ' ' | sed 's/\(^0*\)\|\(\b0*\)//g'))
            # show
			if [[ "$gps_fix" != "V" ]]
			then
				echo $ts ${gps_pos[@]} >> $DATAFILE
				sleep 5s
			fi
		fi
	fi

done < /dev/ttyAMA0