Rubyさまの言うとおりscript

eeny_meeny_miny_moe.rb

require "csv"

WANT_TO_DO_CSV = "./want_to_do.csv" # やりたいことリストを準備しておく
HISTORY_CSV = "./history.csv"

puts "Eeny, meeny, miny, moe"
old_history = CSV.read(HISTORY_CSV, headers: true)
@today_pickup_todo = nil

def pickup_todo
  @today_pickup_todo = [Date.today.to_s, CSV.read(WANT_TO_DO_CSV).flatten.sample]
end

new_history = CSV.open(HISTORY_CSV, 'w')
  new_history.puts ["date", "what_todo"]
  old_history.each do |log|
    if log["date"] == Date.today.to_s
      new_history.puts pickup_todo
    else
      new_history.puts log
    end
  end
  new_history.puts pickup_todo if @today_pickup_todo.nil?
new_history.close

puts "Your todo: #{@today_pickup_todo[1]}"