#!/usr/bin/perl
use strict;
use warnings;

# start
my $t0 = time();

my $file1   = 'file1.txt';
my $file2   = 'file2.csv';
my $outfile = 'final_lines.txt';

# run once
#testdata();

my %file2=();
open FILE2,  '<',$file2 or die "Could not open $file2 $!";
while (<FILE2>){
  s/[\r\n]//g;
  $file2{$_} = 1;
}
my $dur = time() - $t0;
print "$. records read from $file2 in $dur seconds\n";
close FILE2;
$t0 = time();

open OUTFILE,'>',$outfile or die "Could not open $outfile $!";
open FILE1,  '<',$file1 or die "Could not open $file1 $!";
my $count_out=0;
while (<FILE1>){
  my ($id,undef) = split /:/;
  if (exists $file2{$id}){
    print OUTFILE $_;
	++$count_out;
  }
}
$dur = time() - $t0;
print "$. records read from $file1 in $dur seconds\n";
close FILE1;
close OUTFILE;
print "$count_out records written to $outfile\n";

# some random data
sub testdata {
 my $count;
 my @char = ('A'..'Z','a'..'z','0'..'9');
 open OUT1,'>',$file1 or die "$file2 $!";
 open OUT2,'>',$file2 or die "$file2 $!";
 for (my $i=1_000_000;$i<=99_999_999;$i+=99){
   my @chars = map{ $char[int(rand(62))] }(1..60);
   my $line = ':'.(join '',@chars);
   print OUT1 ($i + int rand(99))."$line\n";
   print OUT2 ($i + int rand(99))."\n";
   ++$count;
 }
 close OUT1; close OUT2;
 print "$count records created in $file1 and $file2\n";
}