NAME

File::MultipleDiff - Compare multiple files

SYNOPSIS

   use File::MultipleDiff;
   multiple_file_diff ( <input_directory>
                      , <file_names_pattern>
                      , 'c|b'            # c - colour, b - black/white
                      , <max_digits_amount> );

DESCRIPTION

Compares many files with each other. Writes comparison results into a symmetric matrix having amount of rows and amount of columns equal with the amount of compared files. Every matrix element contains amount of differences between corresponding pair of compared files.

If a directory "inp_directory" contains file "file1", ... "file5" and only these files, then the command

   multiple_file_diff ('inp_directory');

produces following output matrix:

   ---------------------------
         |  f   f   f   f   f 
         |  i   i   i   i   i 
         |  l   l   l   l   l 
         |  e   e   e   e   e 
         |  1   2   3   4   5 
   ---------------------------
   file1 |  0   1   2   0   3  
   file2 |  -   0   3   1   4  
   file3 |  -   -   0   2   5  
   file4 |  -   -   -   0   3  
   file5 |  -   -   -   -   0  
 

Amount of different lines in every pair of files is meant as an amount of differences and and these amounts are printed as elements of the matrix.

That means, that file1 is identical with file4, file2 has 4 differences from file5.

Comparison of 2 objects is a commutative operation: its result does not depend on sequence of compared objects. That means, if A is equal with B, than B is equal with A, if A is not equal with B, that B is not equal with A.

This obstacle forces a comparison matrix to be a symmetric one. The entries of a symmetric matrix are symmetric with respect to its main diagonal. See http://en.wikipedia.org/wiki/Symmetric_matrix

For performance's sake a half of the matrix will be filled in.

Example:

   fileA        fileB
   -----        -----
   line1        line1
   line2        line3
   line3        line4
   line4        line5

Perl module Algorithm::Diff is used for file comparison. This module minimizes amount of differences and for the example above it detects 2 (not 3) differences between these files:

   fileA        fileB
   -----        -----
   line1        line1
   line2                 1st difference
   line3        line3
   line4        line4
                line5    2nd difference

A basis of this minimization is the longest common subsequence (LCS) method, that is implemented in that module.

Remark for more curious

Have you noticed a fraud above? Amount of differences between 2 files is strictly speaking not commutative, if Algorithm::Diff is used. Nevertheless I've decided to create a triangular matrix, as if a full matrix were symmetric matrix indeed. This is acceptable for implementation of this module as a "chaosmeter". Assume, you expectation is that some kind of configuration files on many computers must be identical and you want to check this. Hopefully most of them might be identical, but some of them are different. Zeroes in the matrix mean identical files and identity check is commutative operation. Non-zeroes matrix elements mean divergence of file contents and a level of chaos. The larger matrix element, the larger distance between 2 files. A known from mathematics metric or distance function is similar with a conversion, made by Algorithm::Diff. Absent commutativity is known as quasimetric. Quote from http://en.wikipedia.org/wiki/Metric_(mathematics)#Quasimetrics "Quasimetrics are common in real life. ... Example is a taxicab geometry topology having one-way streets, where a path from point A to point B comprises a different set of streets than a path from B to A."

EXPORT

   multiple_file_diff

SUBROUTINES

multiple_file_diff

   multiple_file_diff (
       <input_directory>      # Directory, that contains all compared files;

     , <file_name_pattern>    # Regular expression, optional parameter,
                              # default value - all files in the input directory;
                             
     , 'c|b'                  # Refers to output of comparison, optional.
                              # c - colour, b - black/white output (b is default).
                              # Prerequisite for usage of colour mode is that
                              # terminal supports ANSI escape sequences.
                              # More about is here
                              # http://search.cpan.org/~rra/Term-ANSIColor-4.02/ANSIColor.pm ;

     , <max_digits_amount> ); # Max amount of digits in amounts of differences.
                              # Optional parameter, default value is 2.
                              # This parameter is self expandable and supports
                              # amount of differences until 9999.
                              # You can ignore the last parameter.

Only 1st parameter of this subroutine must be specified. Undefined or empty further parameters will be replaces by default values.

AUTHOR

Mart E. Rivilis, rivilism@cpan.org

BUGS

Please report any bugs or feature requests to bug-file-multiplediff@rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=File-MultipleDiff. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT

You can find documentation for this module with the perldoc command.

   perldoc File::MultipleDiff

You can also look for information at:

• RT: CPAN's request tracker (report bugs here)

   http://rt.cpan.org/NoAuth/Bugs.html?Dist=File-MultipleDiff

• AnnoCPAN: Annotated CPAN documentation

   http://annocpan.org/dist/File-MultipleDiff

• CPAN Ratings

   http://cpanratings.perl.org/d/File-MultipleDiff

• Search CPAN

   http://search.cpan.org/dist/File-MultipleDiff/

LICENSE AND COPYRIGHT

Copyright 2013 Mart E. Rivilis. This program is free software; you can redistribute it and/or modify it under the terms of the the Artistic License (2.0).

cpanm File::MultipleDiff

perl -MCPAN -e shell
install File::MultipleDiff