Ignore empty lines in a CSV file using Perl - perl

Question

I have to read a CSV file, abc.csv, select a few fields from them and form a new CSV file, def.csv.
Below is my code. I am trying to ignore empty lines from abc.csv.
genNewCsv();
sub genNewCsv {
my $csv = Text::CSV->new();
my $aCsv = "abc.csv"
my $mCsv = "def.csv";
my $fh = FileHandle->new( $aCsv, "r" );
my $nf = FileHandle->new( $mCsv, "w" );
$csv->print( $nf, [ "id", "flops""ub" ] );
while ( my $row = $csv->getline($fh) ) {
my $id = $row->[0];
my $flops = $row->[2];
next if ( $id =~ /^\s+$/ ); #Ignore empty lines
my $ub = "TRUE";
$csv->print( $nf, [ $id, $flops, $ub ] );
}
$nf->close();
$fh->close();
}
But I get the following error:
Use of uninitialized value $flops in pattern match (m//)
How do I ignore the empty lines in the CSV file?
I have used Stack Overflow question Remove empty lines and space with Perl, but it didn't help.

Answer 1

You can skip the entire row if any fields are empty:
unless(defined($id) && defined($flop) && defined($ub)){
next;
}
You tested if $id was empty, but not $flops, which is why you got the error.
You should also be able to do
unless($id && $flop && $ub){
next;
}
There, an empty string would evaluate to false.
Edit: Now that I think about it, what do you mean by ignore lines that aren't there?
You can also do this
my $id = $row[0] || 'No Val' #Where no value is anything you want to signify it was empty
This will show a default value for the the variable, if the first value evaluated to false.

Answer 2

Run this on your file first to get non-empty lines
sub removeblanks {
my #lines = ();
while(#_) {
push #lines, $_ unless( $_ =~ /^\s*$/ ); #add any other conditions here
}
return \#lines;
}

Answer 3

You can do the following to skip empty lines:
while (my $row = $csv->getline($fh)){
next unless grep $_, #$row;
...

Answer 4

You could use List::MoreUtils to check if any of the fields are defined:
use List::MoreUtils qw(any);
while(my $row = ...) {
next unless any { defined } #{ $row };
...
}