Ruby Script to get timestamp from FIlename & rename the file to a common format

File_rename.rb

require 'time'

names = []
Dir.glob('*').select { |f| File.file?(f)}.each do |fn|
  file_name = fn.gsub('_', '')
  timestamp = Time.parse(file_name[file_name.index('20200'), 14])
  ext = file_name.split(".").last.downcase
  if ext == "mp4"
    new_file_name = timestamp.strftime("VID%Y%m%d-%H%M%S")
  else
    new_file_name = timestamp.strftime("IMG%Y%m%d-%H%M%S")
  end 
  new_file_name = new_file_name+'.'+ext
  if names.include?(new_file_name)
    new_file_name = new_file_name + '_2.' + ext
  end

  if names.include?(new_file_name)
    puts "Failed for: #{new_file_name}" 
    exit
  end

  names.push(new_file_name)
  if (fn != new_file_name)
    puts "mv #{fn} #{new_file_name}"
    system "mv #{fn} #{new_file_name}"
  end
end