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Re: compare two files by column and return second (matching) column

by aitap (Curate)
on Aug 06, 2012 at 19:32 UTC ( #985805=note: print w/replies, xml ) Need Help??

in reply to compare two files by column and return second (matching) column

Firstly, a couple of advices:
my $in1 = $ARGV[0]; my $in2 = $ARGV[1]; my $fout = $ARGV[2];
It can be simplified into: my ($in1, $in2, $fout) = @ARGV;
open ONE, $in1; open TWO, $in2; open foutname, ">$fout";
You need to check for errors; it's also safer to use three-argument form of open() (imagine someone specifying '/bin/rm -rf / |' as file name). Thus,
open my $one, '<', $in1 || die "$in1: $!\n"; open my $two, '<', $in2 || die "$in2: $!\n"; open my $foutname, ">", $fout || die "$fout: $!\n";
Secondly, when you need to match something to something, think of a hash. Thus,
my %first; while (<$one>) { chomp; my @data = split /\t/; $first{$data[0]}=$data[1]; # fill the hash with the values from the f +irst file } close $one; while (<$two>) { chomp; # just search the hash for these strings exists $first{$_} && print $foutname $first{$_},'\n'; } close $two; close $foutname || warn "$fout: $!\n';
(the code is untested, feel free to ask about errors it gives)
Sorry if my advice was wrong.

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