Crontab of Linux commands

crontab command:

Crontab-l: Show Scheduled Tasks list

CRONTAB-E: Editing a timed task

Crontab-r: Delete all Scheduled Tasks

basic format :  
* * * * * COMMAND 
time-of-day weekly command  
1th List　　1~59 minutes per minute with * or */1 for   the
2nd column represents the hour 1~23 (0 for 0 points)  
The 3rd column represents the date 1~31 
The 4th column represents the month 1~12 
　　5th Column Identification Number Week 0~6 (0 = Sunday)  
6th column to run command  
crontab file example :  
* * * * */USR/LOCAL/ETC/RC.D/LIGHTTPD restart 
The above example shows that 21:30 restarts Apache per night.  
4 1,10,22 * */USR/LOCAL/ETC/RC.D/LIGHTTPD restart 
The example above indicates that 4:45 restarts Apache per month for 1, 10, 22nd.  
1 * * 6,0/usr/local/etc/rc.d/lighttpd restart 
The example above shows that 1:10 restarts Apache per Saturday and Sunday.  
0,30 18-23 * * */usr/local/etc/rc.d/lighttpd restart 
The example above shows that Apache restarts every 30 minutes from 18:00 to 23:00 every day.  
0 * * 6/usr/local/etc/rc.d/lighttpd restart 
The example above indicates that Apache restarts every Saturday.  
* */1 * * * */USR/LOCAL/ETC/RC.D/LIGHTTPD restart 
Restart apache  every hour;
* 23-7/1 * * */US

When the program is executed at the time you specify, the system will send you a letter showing what the program is doing, and if you do not wish to receive such a letter, please leave a blank in each line
After adding >/dev/null 2>&1 can be

Crontab of Linux commands