A backup script that backups the folder you wish into a 7z file, sort of versioning done stupid

SmartStupidVersioning.rb

# Author: babinho
# Name: SmartBackup
# Purpose: A friend needed a fast schedulable solution for directory backup
# and i made it worse :) The script is x-platform, haven't tryed on a mac because
# i am one short. Only prerequisite is 7zip archiver that is in system path
# Executing: ruby smart_backup.rb path(/home/username/dir_to_backup)
# it creates a dir_to_backup.7z file with current date in the name

@in_dir = ARGV[0] 
separator = RUBY_PLATFORM.downcase.include?("mingw") ? "\\" : "/"
@filename = @in_dir[@in_dir.rindex(separator)+1..@in_dir.length]
@out_dir = @in_dir[0..@in_dir.rindex(separator)]

def backup
  files = Dir.entries(@out_dir)
  filename = "#{@filename}-#{Time.now.strftime('%Y-%m-%d')}"
  fout = filename
  i = 1
  until files.grep(/#{fout}/).empty?
    fout = filename+"_#{i.to_s}"
    i += 1
  end
  if RUBY_PLATFORM.downcase.include?("mingw")
    command = "7z.exe a -m0=lzma2 -mmt4"
  else
    command = "7za a -m0=lzma2 -mmt4"
  end
  system("#{command} #{@out_dir+fout}.7z #{@in_dir}")
  puts "backup finished"
end
backup