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

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

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
[download]

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
[download]

 
#!/usr/bin/perl

use strict; use warnings;

use Text::Diff;

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

print $diffs;
[download]

Comment on Compare two txt files and print the difference between the two files. Select or Download Code

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Re: Compare two txt files and print the difference between the two files. by Kenosis (Priest) on Feb 01, 2013 at 18:25 UTC
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;` [download] Output on your data sets: `http://www.ok.com/test_1234.html http://www.ok.com/test_error.html` [download] Hope this helps!	[reply] [d/l] [select]
Re: Compare two txt files and print the difference between the two files. by trizen (Hermit) on Feb 01, 2013 at 17:06 UTC
`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', $_}; }` [download]	[reply] [d/l]
Re^2: Compare two txt files and print the difference between the two files. by Anonymous Monk on Apr 05, 2017 at 17:45 UTC
Great script! Thanks	[reply]
Re: Compare two txt files and print the difference between the two files. by Lotus1 (Vicar) on Feb 01, 2013 at 18:41 UTC
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` [download]	[reply] [d/l]
Re: Compare two txt files and print the difference between the two files. by 7stud (Deacon) on Feb 02, 2013 at 02:33 UTC
`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` [download]	[reply] [d/l]