module IRB::HistorySavingAbility

def save_history
  history = self.class::HISTORY
  if num = IRB.conf[:SAVE_HISTORY] and (num = num.to_i) != 0
    if history_file = IRB.conf[:HISTORY_FILE]
      history_file = File.expand_path(history_file)
    end
    history_file = IRB.rc_file("_history") unless history_file
    # Change the permission of a file that already exists[BUG #7694]
    begin
      if File.stat(history_file).mode & 066 != 0
        File.chmod(0600, history_file)
      end
    rescue Errno::ENOENT
    rescue Errno::EPERM
      return
    rescue
      raise
    end
    if File.exist?(history_file) &&
       File.mtime(history_file) != @loaded_history_mtime
      history = history[@loaded_history_lines..-1] if @loaded_history_lines
      append_history = true
    end
    File.open(history_file, (append_history ? 'a' : 'w'), 0o600, encoding: IRB.conf[:LC_MESSAGES]&.encoding) do |f|
      hist = history.map{ |l| l.split("\n").join("\\\n") }
      unless append_history
        begin
          hist = hist.last(num) if hist.size > num and num > 0
        rescue RangeError # bignum too big to convert into `long'
          # Do nothing because the bignum should be treated as inifinity
        end
      end
      f.puts(hist)
    end
  end
end