Parsing a .gpx file with Geo::Gpx

paulmorrow has asked for the wisdom of the Perl Monks concerning the following question:

I am attempting to parse a .gpx document and referencing the script below (thanks to Simbabque), the current error I am receiving is:

Can't use an undefined value as an ARRAY reference at gpxscript2 line 19.

I have just begun reading about arrays in my Beginning Perl book and am stuck. I read that the array must start with an alpha character or an underscore. I attempted to label the array and reconfigure this line with no luck... Any suggestions would be appreciated. I am using Ubuntu 12.04, and installed the Geo::Gpx,DateTime::Format::ISO8601, & XML::Descent successfully

Here is the script: Thanks!

use strict;
use warnings;
use Geo::Gpx;
use DateTime;
# Open the GPX file
open my $fh_in, '<', 'fells_loop.gpx';
# Parse GPX
my $gpx = Geo::Gpx->new( input => $fh_in );
# Close the GPX file
close $fh_in;

# Open an output file
open my $fh_out, '>', 'fells_loop.csv';
# Print the header line to the file
print $fh_out "time,lat,lon,ele,name,sym,type,desc\n";

# The waypoints-method of the GEO::GPX-Object returns an array-ref
# which we can iterate in a foreach loop
foreach my $wp ( @{ $gpx->waypoints() } ) {
  # Some fields seem to be optional so they are missing in the hash.
  # We have to add an empty string by iterating over all the possible
  # hash keys to put '' in them. Map is like a foreach loop.
  map { $wp->{$_} ||= '' } qw( time lat lon ele name sym type desc );

  # The time is a unix timestamp, which is hard to read.
  # We can make it an ISO8601 date with the DateTime module.
  # We only do it if there already is a time, though.
  if ($wp->{'time'}) {
    $wp->{'time'} = DateTime->from_epoch( epoch => $wp->{'time'} )
                             ->iso8601();
  }
  # Join the fields with a comma and print them to the output file
  print $fh_out join(',', (
    $wp->{'time'},
    $wp->{'lat'},
    $wp->{'lon'},
    $wp->{'ele'},
    $wp->{'name'},
    $wp->{'sym'},
    $wp->{'type'},
    $wp->{'desc'},
  )), "\n"; # Add a newline at the end
}
# Close the output file
close $fh_out;
[download]

Comment on Parsing a .gpx file with Geo::Gpx Download Code

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Re: Parsing a .gpx file with Geo::Gpx by CountZero (Bishop) on Jun 27, 2012 at 21:16 UTC
Most probably the `$gpx` object variable was not initialized correctly. Probably the gpx-file was not read correctly. Add an "`or die "Error in opening gpx file: $!;` to line 6 and run the script again. Update: deleted a spurious double quote. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply] [d/l] [select]
Re^2: Parsing a .gpx file with Geo::Gpx by paulmorrow (Initiate) on Jun 27, 2012 at 22:05 UTC
Count Zero, thanks for your reply, I inserted your text one space after the last word in line 6: "or die "Error is opening gpx file: $!; as you had instructed, with no luck, the error is below. I also tried some different combinations of positioning the " quotation marks and leaving them out all together. paul@intern-PM:~/Desktop/San Diego$ perl gpxscript2 String found where operator expected at gpxscript2 line 6, near "'sandiegopark.gpx' "or die "" (Missing operator before "or die "?) Bareword found where operator expected at gpxscript2 line 6, near ""or die "Error" (Missing operator before Error?) syntax error at gpxscript2 line 6, near "'sandiegopark.gpx' "or die "" Global symbol "$fh_in" requires explicit package name at gpxscript2 line 8. Execution of gpxscript2 aborted due to compilation errors. with no quotes I receive the message: paul@intern-PM:~/Desktop/San Diego$ perl gpxscript2 syntax error at gpxscript2 line 6, near "file:" Global symbol "$fh_in" requires explicit package name at gpxscript2 line 8. Execution of gpxscript2 aborted due to compilation errors. Sorry, I'm not sure how to proceed from here. I was also looking at a XML parser, for you can do a save as .xml, do you suggest something like that?	[reply]
Re^3: Parsing a .gpx file with Geo::Gpx by CountZero (Bishop) on Jun 28, 2012 at 06:36 UTC
That line should read: `open my $fh_in, '<', 'fells_loop.gpx' or die "Error in opening gpx fil +e: $!";` [download] Try it and see what error you get. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply] [d/l]
Re^3: Parsing a .gpx file with Geo::Gpx by frozenwithjoy (Priest) on Jun 27, 2012 at 23:34 UTC
I'm not sure what the code looks like when you have it "without quotes", so to remove any confusion, could you revert to the script as it was without out the "or die" stuff and just add `use autodie;` to the top? What, if any, errors do you get now? Thanks.	[reply] [d/l]