⏰Crontab

What's crontab?

The cron command-line utility is a job scheduler on Unix-like operating systems. Users who set up and maintain software environments use cron to schedule jobs (commands or shell scripts), also known as cron jobs, to run periodically at fixed times, dates, or intervals.

Format

Min  Hour Day  Mon  Weekday
*    *    *    *    *  {command to be executed}
┬    ┬    ┬    ┬    ┬
│    │    │    │    └─  Weekday  (0=Sun .. 6=Sat)
│    │    │    └──────  Month    (1..12)
│    │    └───────────  Day      (1..31)
│    └────────────────  Hour     (0..23)
└─────────────────────  Minute   (0..59)

---

Operators	Description
*	all values
,	separate individual values
-	a range of values
/	divide a value into steps

---

Crontab

# Adding tasks easily
echo "@reboot echo hi" | crontab

# Open in editor
crontab -e

# List tasks
crontab -l [-u user]

---

Examples

Format example	Description
0 * * * *	every hour
*/15 * * * *	every 15 minutes
0 */2 * * *	every 2 hours
0 18 * * 0-6	every week Mon-Sat at 6pm
10 2 * * 6,7	every Sat and Sun on 2:10am
0 0 * * 0	every Sunday midnight
@reboot	every reboot