ruby gems for cron job

 1.gem Whenever  
 2.gem Craken  
 3.gem delayed_job (longer job)  
 4.gem Rufus scheduler  
 5.gem backgroundrb (run scheduled tasks as well as tasks that take too long for the normal client/server relationship)  
 6. gem resque-scheduler  
 7. rake approach  
 8. gem daemons  
 whenever  
 http://subhashmohan.wordpress.com/2010/03/27/rails-crontab-with-whenever-gem/  
 http://dzoba.com/162/  
 https://shellycloud.com/documentation/running_periodic_tasks  
 http://learnaholic.me/2012/10/10/backing-up-postgresql-with-backup-and-whatever-gems/  
 http://ruthienachmany.github.io/blog/2013/08/10/sidekiq-redis-cron-jobs/  
 http://blog.wyeworks.com/2009/8/10/scheduling/  
 http://rubydoc.info/github/javan/whenever/frames (HHH)  
 http://eewang.github.io/blog/2013/03/12/how-to-schedule-tasks-using-whenever/(HHH)  
 http://stackoverflow.com/questions/285717/a-cron-job-for-rails-best-practices(HHH)