Compare the contents of two folders

compare_folders.rb

#!/usr/bin/env ruby
# encoding: utf-8

require 'fileutils'

errors = []
folderA = 'folder1'
folderB = 'folder2'

# list all files in each folder
filesFolderA = Dir["./#{folderA}/*.txt"]
filesFolderB = Dir["./#{folderB}/*.txt"]

if filesFolderA.size != filesFolderB.size
  errors << "Number of files in folders is different. A: #{filesFolderA.size} files, B: #{filesFolderB.size} files."
end

filesFolderA.sort!
filesFolderB.sort!

# create a list of filenames
namesA = filesFolderA.map do |a|
  a.gsub("./#{folderA}/",'')
end

namesB = filesFolderB.map do |b|
  b.gsub("./#{folderB}/",'')
end

# find the missing files in folder A
missingFilesA = namesB - namesA
if missingFilesA.size > 0
  errors << "Missing files on folder '#{folderA}': #{missingFilesA.join(', ')}"
end

# find missing files in folder B
missingFilesB = namesA - namesB
if missingFilesB.size > 0
  errors << "Missing files on folder '#{folderB}': #{missingFilesB.join(', ')}"
end

# compare files
maxItems = [filesFolderA.size, filesFolderB.size].max
first = filesFolderA
second = filesFolderB
if filesFolderB.size == maxItems
  first = filesFolderB
  second = filesFolderA
end

first.zip(second) do |pair|
  if not pair.first.nil? and not pair.last.nil?
    if not FileUtils.compare_file(pair.first.to_s, pair.last.to_s)
      errors << "\"#{pair.first}\" is different from \"#{pair.last}\""
    end
  end
end

puts "=" * 20
puts errors
puts "=" * 20