#!/usr/bin/perl

foreach $file (@ARGV){
    if($file =~ /(\d\d\d\d)(\d\d)(\d\d)_(\d\d\d\d\d\d)\.txt$/i){
        $zda = "\$--ZDA,$4.00,$3,$2,$1,00,00\n";
        $gpx = $file;
        $gpx =~ s/\.txt$/.gpx/i;

        if(! open(BABEL,"|gpsbabel -i nmea -f - -o gpx -F $gpx") ){
            print STDERR "failed to open gpsbabel for $gpx\n";
            next;
        }
        if(! open(NMEA,"$file") ){
            print STDERR "failed to read $file\n";
            next;
        }

        print BABEL $zda;
        while(<NMEA>){
            print BABEL $_;
        }

        close BABEL;
        close NMEA;
    }else{
        print STDERR "bad filename $file\n";
    }
}