Crontab Commands
Crontab is the utility used for scheduled any script and job in the Operating System Level. It comes with the Linux, HP-UX , Unix and Other Operating System.
It is very usefully utility for scheduling purpose.
To list or display all the scheduled job in crontab:
crontab -l
To add entry or change in existing job in crontab:
crontab -e
Backup of Crontab:
crontab -l > crontab_new
it will make a copy of crontab into crontab_new file.
Restore of Crontab:
crontab crontab_new
It will set crontab_new as crontab
example:
———–
0 5 * * * sh backup.sh
* * * * * command to be executed
– – – – –
| | | | |
| | | | +—– day of week (0 – 6) (Sunday=0)
| | | +——- month (1 – 12)
| | +——— day of month (1 – 31)
| +———– hour (0 – 23)
+————- min (0 – 59)
Example for scheduling
* * * * * #Runs every minute
30 * * * * #Runs at 30 minutes past the hour
15 8 * * * #Runs at 8:15 am every day
15 20 * * * #Runs at 8:15 pm every day
00 14 * * 0 #Runs at 2:00 pm every Sunday
00 5 * * Sun #Runs at 5:00 am every Sunday
30 8 1 * * #Runs at 8:30 am on the first day of every month
00 0-23/2 01 * * #Runs every other hour on the first of every moth
00 * * * * #Runs on every hour
