Compare two txt files and print the difference between the two files.

[Anonymous Monk]

Hi Monks!
I am trying to compare two text files with a bunch of links in each line, I would like to know what is not on the second file that is on the second file. Print the difference between the two files. I am using this code but It doesn't make sense on the results I’m getting, ma someone has a better way of doing this. Here is the code I am using:

a_file.txt sample:
http://www.ok.com/test_www.pdf       
http://www.ok.com/test_1234.html        
http://www.ok.com/test_part.pdf       
http://www.ok.com/test_345.pdf       
http://www.ok.com/test_error.html

b_file.txt sample:
http://www.ok.com/test_www.pdf              
http://www.ok.com/test_part.pdf       
http://www.ok.com/test_345.pdf

 
#!/usr/bin/perl

use strict; use warnings;

use Text::Diff;

my $diffs = diff 'a_file.txt' => 'b_file.txt';

print $diffs;

[Kenosis]

If I'm understanding you correctly, you're interested in finding all items in the first file that are not in the second file. If this is the case, List::Compare can assist you with this:

use strict;
use warnings;
use File::Slurp qw/read_file/;
use List::Compare;

chomp( my @a_file = read_file 'a_file.txt' );
chomp( my @b_file = read_file 'b_file.txt' );

my @a_file_only = List::Compare->new( \@a_file, \@b_file )->get_Lonly;

print "$_\n" for @a_file_only;

Output on your data sets:

http://www.ok.com/test_1234.html
http://www.ok.com/test_error.html

Hope this helps!

[trizen]

use strict;
use warnings;

my $first_file  = shift || 'a.txt';
my $second_file = shift || 'b.txt';

open my $a_fh, '<', $first_file  or die "$first_file: $!";
open my $b_fh, '<', $second_file or die "$second_file: $!";

my %second_file;
@second_file{map { unpack 'A*', $_ } <$b_fh>} = ();

while (<$a_fh>) {
    print unless exists $second_file{unpack 'A*', $_};
}

[Anonymous Monk]

Great script! Thanks

[Lotus1]

The code you presented in the OP worked fine for me. I assume the problem you had understanding the output was due to the differences in whitespace at the ends of the lines in your sample text files. The whitespace made some of the lines appear to be different. Once I removed the extra whitespace here is the output which makes sense to me:

--- a_file.txt    Fri Feb  1 13:30:39 2013
+++ b_file.txt    Fri Feb  1 13:30:55 2013
@@ -1,6 +1,4 @@
-a_file.txt sample:
+b_file.txt sample:
 http://www.ok.com/test_www.pdf
-http://www.ok.com/test_1234.html
 http://www.ok.com/test_part.pdf
 http://www.ok.com/test_345.pdf
-http://www.ok.com/test_error.html

[7stud]

use strict;
use warnings;
use 5.012;

my $fname = 'a.txt';

open my $afile, "<", $fname
    or die "Couldn't open $fname: $!";

my %a_links;

while (my $link = <$afile>) {
    chomp $link;
    $a_links{$link} = undef;
}

close $afile;
$fname = 'b.txt';

open my $bfile, "<", $fname
    or die "Couldn't open $fname: $!";

while (my $link = <$bfile>) {
    chomp $link;
    next if exists $a_links{$link}; 
    say $link;
}

close $bfile;


--output:--
http://www.ok.com/test_www.pdf              
http://www.ok.com/test_345.pdf