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Full Discussion: Honey, I broke awk! (duplicate line removal in 30M line 3.7GB csv file)
Top Forums Shell Programming and Scripting Honey, I broke awk! (duplicate line removal in 30M line 3.7GB csv file) Post 302895685 by Chubler_XL on Tuesday 1st of April 2014 07:22:33 PM
Old 04-01-2014
This updated version checks for different lines that have the same MD5 and fails with an exit code so at least you can be confident nothing is wrong. This needs a filename parameter as it needs random access and streams don't support that.

Code:
#!/usr/bin/perl -w
use Digest::MD5 qw(md5);
open(DATA, "<", $ARGV[0]) || die "Can't open $ARGV[0]: $!";

my %seen;
while (1) {
  my $pos = tell DATA;
  my $line=<DATA>;
  last unless defined $line;
  my $crc= md5($line);
  if(!$seen{$crc}) {
     $seen{$crc}=$pos+1;
         print $line;
  } else {
      $pos = tell DATA;
      seek DATA, $seen{$crc}-1, 0;
          $!=255;
          die "Duplicate CRC found" unless (<DATA> eq $line);
          seek DATA, $pos, 0;
  }
}

This User Gave Thanks to Chubler_XL For This Post:
Michael Stora
 

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LEARN ABOUT MOJAVE

io::digest

IO::Digest(3)						User Contributed Perl Documentation					     IO::Digest(3)

NAME

       IO::Digest - Calculate digests while reading or writing

SYNOPSIS

	use IO::Digest;

	# Get a Digest::MD5 object that takes input while $fh being written or read
	my $fh;
	my $iod = IO::Digest->new ($fh, 'MD5');

	print $fh "fooo";
	print $iod->hexdigest

DESCRIPTION

       This module allows you to calculate digests while reading or writing file handles.  This avoids the case you need to reread the same
       content to compute the digests after written a file.

TEST COVERAGE

	----------------------------------- ------ ------ ------ ------ ------ ------
	File				      stmt branch   cond    sub   time	total
	----------------------------------- ------ ------ ------ ------ ------ ------
	blib/lib/IO/Digest.pm		     100.0    n/a    n/a  100.0  100.0	100.0
	Total				     100.0    n/a    n/a  100.0  100.0	100.0
	----------------------------------- ------ ------ ------ ------ ------ ------

AUTHORS

       Chia-liang Kao <clkao@clkao.org>

COPYRIGHT

       Copyright 2004 by Chia-liang Kao <clkao@clkao.org>.

       This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

       See <http://www.perl.com/perl/misc/Artistic.html>

perl v5.18.2							    2013-02-16							     IO::Digest(3)
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