Cron

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

Operator	Description
*	All values
,	Separate individual values
-	A range of values
/	Divide a value into steps

Special strings

String	Description
@reboot	every reboot
@hourly	once every hour - same as `0 * * * *`
@daily	once every day - same as `0 0 * * *`
@midnight	once every midnight - same as `@daily`
@weekly	once every week - same as `0 0 * * 0`
@monthly	once every month - same as `0 0 1 * *`
@yearly	once every year - same as `0 0 1 1 *`

Examples

Command	Description
0 * * * *	Every hour
/15 * * *	Every 15 mins
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

Crontab

Adding tasks easily

 
echo "@reboot echo hi" | crontab

Open in editor - optional for another user

 
crontab -e [-u user]

List tasks - optional for another user

 
crontab -l [-u user]

Delete crontab file - optional for another user

 
crontab -r [-u user]

Follow me on : Medium Linkedin Researchgate