crontab command format

1th column min 1~59
2nd Hour 1~23 (0 = midnight)
3rd Liege 1~31
4th Column Month 1~12
5th Column Week 0~6 (0 = Sunday)
6th List of commands to run

Here is the format for crontab:
Time-sharing day and month command to run

Here are some examples of crontab file entries:

21:30 restart Apache per night:

* * * * */usr/local/apache/bin/apachectl restart

4:45 restarts Apache on 1, 10, 22nd of each month:

4 1,10,22 * */usr/local/apache/bin/apachectl restart

1:10 restarts Apache per Saturday, Sunday:

1 * * 6,0/usr/local/apache/bin/apachectl restart

Restart Apache every 30 minutes from 18:00 to 23:00 every day:

0,30 18-23 * * */usr/local/apache/bin/apachectl restart

The above example shows the restart of Apache for every Saturday at 11:00AM:

0 * * 6/usr/local/apache/bin/apachectl restart

Restart Apache every hour:

* */1 * * * */usr/local/apache/bin/apachectl restart

From 11 o'clock to 7 in the morning, restart Apache every hour:

* 23-7/1 * * * */usr/local/apache/bin/apachectl restart

4th per month with 11-point restart from Monday to Wednesday Apache:

0 4 * Mon-wed/usr/local/apache/bin/apachectl restart

4-point restart of Apache on January 1

0 4 1 Jan */usr/local/apache/bin/apachectl restart

crontab command format