Cron

cron is a time-based job scheduler in Unix-like computer operating systems. cron enables users to schedule jobs (commands or shell scripts) to run periodically at certain times or dates

Entry	Description	Equivalent To
@yearly (or @annually)	Run once a year, midnight, Jan. 1st	0 0 1 1 *
@monthly	Run once a month, midnight, first of month	0 0 1 * *
@weekly	Run once a week, midnight on Sunday	0 0 * * 0
@daily	Run once a day, midnight	0 0 * * *
@hourly	Run once an hour, beginning of hour	0 * * * *
@reboot	Run at startup

*    *    *    *    *  command to be executed
┬    ┬    ┬    ┬    ┬
│    │    │    │    │
│    │    │    │    │
│    │    │    │    └───── day of week (0 - 6) (0 is Sunday, or use names)
│    │    │    └────────── month (1 - 12)
│    │    └─────────────── day of month (1 - 31)
│    └──────────────────── hour (0 - 23)
└───────────────────────── min (0 - 59)

crontab - l = list

crontab -e = edit

crontab -r = removes crontab directory

crontab -u username -l

So in terminal print ‘Hello’ every 5 minutes..


# MIN   HOUR   MDAY  MON  DOW   COMMAND 
   */5     *      *     *    *    echo 'Hello'