Hi, I am fairly new to Perl and am running into a problem that I hope the Perl Monks can help shed some light on.

I am trying to add a column to an existing file with hundreds of columns and hundreds of thousands of rows. For what it's worth, these files have the same number of rows. The rows also correspond to each other. The file which I am appending a single column has the line number in the first column. (I am appending the second column.)

The following code that works, but it takes forever and I will need to do this daily. I am sure there are several inefficiencies and it seems there has to be a faster way.

use warnings;
use strict;

open (OUTFILE, ">outfile.csv");
open (IN1, "<infile1.csv");
 
my $counter = 0;
 
while (<IN1>){
chomp;
print OUTFILE $_;

open (IN2, "<infile2.csv");
while (<IN2>){
my @f = split(/,/);
if ($counter == $f[0]){
print OUTFILE ",$f[1]\n";
}}
close IN2;
$counter = $counter + 1;
}

close IN1;
close OUTFILE;
[download]

Thanks in advance!

Scott

Thanks for all the help. To clarify, the numbered file was in order.

This is the code that seemed to work best (similar to jwkrahn's code).

use warnings;
use strict;
 
 
open my $in2, '<', 'infile2.csv' or die "Cannot open 'infile2.csv' bec
+ause: $!";
 
my %data;
while ( <$in2> ) {
    my ( $key, $value ) = split /,/;
    $data{ $key } = $value;
    }
 
close $in2;
 
 
open my $outfile, '>', 'outfile.csv' or die "Cannot open 'StatsCubeR2f
+ormat.csv' because: $!";
open my $in1, '<' , 'infile1.csv' or die "Cannot open 'infile1.csv' be
+cause: $!";
 
while ( <$in1> ) {
    chomp;
    print $outfile "$_";
    if ( exists $data{ $. - 1 } ) {
        print $outfile ",$data{$. - 1}\n";
        }
    else {
                print $outfile ",field_name\n";
                }
    }
 
close $in1;
close $outfile;
[download]

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