David Newman wrote:
>
> Greetings. I have a working script (pasted below) that uses
> List::Compare to find common lines in two files.
>
> Now I am again looking to compare two files but this time exclude any
> lines in file 1 that appear in file 2. I don't see anything in the
> List::Compare documentation on how to do this.
>
> Thanks in advance for any clues on a simple way to handle this.
>
> dn
>
> #!/usr/bin/perl -w
>
> use strict;
You should also use the warnings pragma instead of the command-line switch.
use warnings;
> use List::Compare;
>
> my $lfile = $ARGV[0];
> my $rfile = $ARGV[1];
It would also be nice to make sure that there are in fact two parameters
die "The parameters must be the the two files for comparison"
unless @ARGV == 2;
> my $lc;
> my @union;
It is best to declare variables as close as possible to their first use. All you
need here is
my ($lfile, $rfile) = @ARGV;
> # get files
> open(DAT, $lfile) or die("unable to open");
>
> my @Llist = <DAT>;
>
> close(DAT);
You should include the $! variable in the die string so that you know why the
open failed. I suggest
my @llist;
{
open my $fh, '<', $lfile or die "Unable to open '$lfile': $!";
@llist = <$fh>;
}
> open(DAT, $rfile) or die("unable to open");
>
> my @Rlist = <DAT>;
>
> close(DAT);
The same applies to the second parameter.
> # do comparison
>
> $lc = List::Compare->new(\...@llist, \...@rlist);
>
> @union = $lc->get_union;
This call doesn't 'find common lines in two files'. It generates a list of lines
that appear at least once in either file.
> foreach my $union (@union) {
> print "$union";
> }
You shouldn't put $union in quotes, and the loop is better written as
print for @union;
It's not clear from your description what new information you want. You say you
want to 'exclude any lines in file 1 that appear in file 2', but you don't say
what you want to exclude those lines from.
I think you must mean either:
- All records that appear at least once in either file, but not in both. In that
case you need
my @difference = $lc->get_LorRonly;
- All records that appear in file 1 but not in file 2. To do that you want
my @file1only = $lc->get_Lonly;
I hope this helps.
Rob
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