Add an external cron-job: Mac OSX and Linux

If you are using Mac or Linux operating systems then you can access the Cron Job scheduler using the following command.

crontab -e

This system uses specific syntax to schedule Cron Job.

Use the following example to define a Cron Job which executes every 15 minutes.  

1.minutes ( 0 - 59 )
2.hour ( 0 - 23 ) 
3.day of the month ( 1 - 31 ) 
4.month ( 1 - 12 ) 
5.day of the week ( 0 - 6 )
6.command to execute   

Example : 

 */15 * * * * wget http://YOUR_SITE_URL/wp-cron.php