Why can't I print a very long string? [closed] - string

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I'm writing a Perl script that searches a kml file and I need to print a very long line of latitude/longitude coordinates. The following script successfully finds the string I'm looking for, but just prints a blank line instead of the value of the string:
#!/usr/bin/perl
# Strips unsupported tags out of a QGIS-generated kml and writes a new one
$file = $ARGV[0];
# read existing kml file
open( INFO, $file ); # Open the file
#lines = <INFO>; # Read it into an array
close(INFO); # Close the file
#print #lines; # Print the array
$x = 0;
$coord_string = "<coordinates>";
# go through each line looking for above string
foreach $line (#lines) {
$x++;
if ( $x > 12 ) {
if ( $line =~ $coord_string ) {
$thisCooordString = $line;
$var_startX = $x;
print "Found coord string: $thisCoordString\n";
print " on line: $var_startX\n";
}
}
}
The file that it's reading is here
and this is the output I get:
-bash-4.3$ perl writekml.pl HUC8short.kml
Found coord string:
on line: 25
Found coord string:
on line: 38
Is there some cap on the maximum length that a string can be in Perl? The longest line in this file is ~151,000 characters long. I've verified that all the lines in the file are read successfully.

Answer 1

You've misspelled the variable name (two os vs three os):
$thisCooordString = $line;
...
print "Found coord string: $thisCoordString\n";
Add use strict and use warnings to your script to prevent these sorts of errors.

Answer 2

Always include use strict and use warnings in EVERY perl script.
If you had done this, you would've gotten the following error message to clue you into your bug:
Global symbol "$thisCoordString" requires explicit package name
Adding these pragmas and simplifying your code results in the following:
#!/usr/bin/env perl
# Strips unsupported tags out of a QGIS-generated kml and writes a new one
use strict;
use warnings;
local #ARGV = 'HUC8short.kml';
while (<>) {
if ( $. > 12 && /<coordinates>/ ) {
print "Found coord string: $_\n";
print " on line: $.\n";
}
}

Answer 3

You can even try with perl one liners as shown below:
Perl One liner on windows command prompt:
perl -lne "if($_ =~ /<coordinates>/is && $. > 12) { print \"Found coord string : $_ \n"; print \" on line : $. \n\";}" HUC8short.kml
Perl One liner on unix prompt:
perl -lne 'if($_ =~ /<coordinates>/is && $. > 12) { print "Found coord string : $_ \n"; print " on line : $. \n";}' HUC8short.kml

Answer 4

As others have pointed out, you need. No, you MUST always use use strict; and use warnings;.
If you used strict, you would have gotten an error message telling you that your variable $thisCoordString or $thisCooordString was not declared with my. Using warnings would have warned you that you're printing an undefined string.
Your whole program is written in a very old (and obsolete) Perl programming style. This is the type of program writing I would have done back in Perl 3.0 days about two decades ago. Perl has changed quite a bit since then, and using the newer syntax will allow you to write easier to read and maintain programs.
Here's your basic program written in a more modern syntax:
#! /usr/bin/env perl
#
use strict; # Lets you know when you misspell variable names
use warnings; # Warns of issues (using undefined variables
use feature qw(say); # Let's you use 'say' instead of 'print' (No \n needed)
use autodie; # Program automatically dies on bad file operations
use IO::File; # Lots of nice file activity.
# Make Constants constant
use constant {
COORD_STRING => qr/<coordinates>/, # qr is a regular expression quoted string
};
my $file = shift;
# read existing kml file
open my $fh, '<', $file; # Three part open with scalar filehandle
while ( my $line = <$fh> ) {
chomp $line; # Always "chomp" on read
next unless $line =~ COORD_STRING; #Skip non-coord lines
say "Found coord string: $line";
say " on line: " . $fh->input_line_number;
}
close $fh;
Many Perl developers are self taught. There is nothing wrong with that, but many people learn Perl from looking at other people's obsolete code, or from reading old Perl manuals, or from developers who learned Perl from someone else back in the 1990s.
So, get some books on Modern Perl and learn the new syntax. You might also want to learn about things like references which can lead you to learn Object Oriented Perl. References and OO Perl will allow you to write longer and more complex programs.