Ignore empty lines in a CSV file using 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.

fyi, you appear to be missing a comma between "flops" and "ub" — Gabs00
– Gabs00, Commented Jan 6, 2014 at 6:26
Move the 'next if ...' one line up, because you Cañons access elements if the line is . — smartmeta
– smartmeta, Commented Jan 6, 2014 at 6:54
Adding to @Gabs00, you have more syntax errors: my $aCsv = "abc.csv" is missing a ;. Copy-Paste mistake? — chrsblck
– chrsblck, Commented Jan 6, 2014 at 7:34

Gabs00 · Accepted Answer · 2014-01-06 06:30:25Z

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.

edited Jan 6, 2014 at 6:30

answered Jan 6, 2014 at 6:17

Gabs00

1,8771 gold badge13 silver badges12 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Zach Leighton · Accepted Answer · 2014-01-06 06:48:57Z

0

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;
}

answered Jan 6, 2014 at 6:48

Zach Leighton

1,94114 silver badges25 bronze badges

Comments

Kenosis · Accepted Answer · 2014-01-06 07:27:31Z

0

You can do the following to skip empty lines:

while (my $row = $csv->getline($fh)){
    next unless grep $_, @$row;
    ...

edited Jan 6, 2014 at 7:27

answered Jan 6, 2014 at 7:02

Kenosis

6,1941 gold badge18 silver badges16 bronze badges

Comments

AKHolland · Accepted Answer · 2014-01-06 18:02:40Z

0

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 };
    ...
}

answered Jan 6, 2014 at 18:02

AKHolland

4,46525 silver badges36 bronze badges

1 Comment

CJ7 Over a year ago

This didn't work for me. I had to use any { $_ eq '' }

Collectives™ on Stack Overflow

Ignore empty lines in a CSV file using Perl

4 Answers 4

Comments

Comments

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related