How to execute tasks on linux on the hour and on the hour-php Tutorial

How does one implement the entire and half-point execution tasks in linux? How does crontab-e in linux set the whole and half-point execution tasks?
It is to execute a task every 30 minutes at the hour, such as and.

Reply to discussion (solution)

*/30 *** tasks

*/30 *** tasks

Great God, if it is now 09:15, how can I execute it once at half past nine and execute it again every 30 minutes to the hour after?

*/30 * curl http://www.xxx.com/controller /region name


This is to execute a request for this address every 30 minutes, that is, the implementation method.
Right?

Don't worry about that 15 minutes.

Then you can schedule the task.
Or write cron. when the date is reached, it can be enabled on time.

The simplest and most crude method is to run the timer once a minute, and then the script determines whether the time is executed.