Task — K-directory diff

Given a few (three or more) directories (non-recursively), display a side-by-side difference of files that are missing from at least one of the directories. Do not display files that exist in every directory.

Since the task is non-recursive, if you encounter a subdirectory, append a '/', but otherwise treat it the same as a regular file.

Examples

Example 1:
Given the following directory structure:
 
dir_a:
Arial.ttf  Comic_Sans.ttf  Georgia.ttf  Helvetica.ttf  
Impact.otf  Verdana.ttf  Old_Fonts/
 
dir_b:
Arial.ttf  Comic_Sans.ttf  Courier_New.ttf
Helvetica.ttf  Impact.otf  Tahoma.ttf  Verdana.ttf
 
dir_c:
Arial.ttf  Courier_New.ttf  Helvetica.ttf  Impact.otf  
Monaco.ttf  Verdana.ttf
 
... the output should look similar to the following:
 
dir_a          | dir_b           | dir_c
-------------- | --------------- | ---------------
Comic_Sans.ttf | Comic_Sans.ttf  |
               | Courier_New.ttf | Courier_New.ttf
Georgia.ttf    |                 |
               |                 | Monaco.ttf
Old_Fonts/     |                 |
               | Tahoma.ttf      |

Analysis

The logic of this is:

• Loop over directories and files
• Find the longest file name (to determine column width)
• Create %files with key = file name and value = a list of the containing directories
• Create a string ($all) that indicates the file is in all directories

Print the heading lines using the longest file name (above) to determine column width and then:

• Loop over directories and files
• Skip file if $files{$file} eq $all
• Print the file name in every column that appears in $files{$file}

Getting the columns to line up is a little messy, made slightly worse by the example have one fewer vertical line than columns. The %-s format in sprintf comes in useful for padding the file names to the right width.

Try it 

Script

#!/usr/bin/perl

# Peter Campbell Smith - 2022-05-23
# PWC 166 task 2

use v5.28;
use strict;
use warnings;
use utf8;

my (@dirs, $dir, $file, $width, $header, $all, %files, $line1, $line2, $prefix);

@dirs = ([qw[Arial.ttf  Comic_Sans.ttf  Georgia.ttf  Helvetica.ttf  Impact.otf  Verdana.ttf  Old_Fonts/]],
         [qw[Arial.ttf  Comic_Sans.ttf  Courier_New.ttf  Helvetica.ttf  Impact.otf  Tahoma.ttf  Verdana.ttf]],
         [qw[Arial.ttf  Courier_New.ttf  Helvetica.ttf  Impact.otf  Monaco.ttf  Verdana.ttf]]);

# loop over directories
$width = 0;
for $dir (0 .. scalar @dirs - 1) {
    
    # loop over files within directory
    for $file (@{$dirs[$dir]}) {
        $files{$file} .= qq[/$dir/];   # if file exists within directory n, $files{$file} matches /n/
        $width = length($file) if length($file) > $width;   # get max file name length
    }
    $all .= qq[/$dir/];   # if $files{$file} eq /0//1//2/ (etc) then file exists in all directories and is skipped below
}

# heading lines
$line1 = qq[\n];
$prefix = ' ';
for $dir (0 .. scalar @dirs - 1) {
    $line1 .= $prefix . 'dir_' . sprintf('%-' . ($width - 4) . 's', chr(ord('a') + $dir)) . ' ';
    $line2 .= $prefix . ('-' x ($width)) . ' ';
    $prefix = '| ';
}
say qq[$line1\n$line2];

# file lines
for $file (sort keys %files) {
    next if $files{$file} eq $all; # skip file if in all directories
    
    # loop over directories
    $prefix = '';
    for $dir (0 .. scalar @dirs - 1) {
        
        # file is in this directory
        if ($files{$file} =~ m|/$dir/|) {
            print sprintf($prefix . " %-${width}s", $file);
        
        # file isn't in this directory
        } else {
            print sprintf($prefix . " %-${width}s", ' ');
        }
    $prefix = ' |';
    }
    print qq[\n];
}
print qq[\n];

Output

 dir_a           | dir_b           | dir_c           
 --------------- | --------------- | --------------- 
 Comic_Sans.ttf  | Comic_Sans.ttf  |                
                 | Courier_New.ttf | Courier_New.ttf
 Georgia.ttf     |                 |                
                 |                 | Monaco.ttf     
 Old_Fonts/      |                 |                
                 | Tahoma.ttf      |