crontab command Explanation

Basic format:
* * * * command
Time-sharing and Lunar Week command
The 1th column represents minutes 1~59 per minute with * or */1
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
The 5th list of the week 0~6 (0 for Sunday)
6th column the command to run
Some examples of crontab files:
* * * */usr/local/etc/rc.d/lighttpd restart
The above example represents 21:30 restart Apache per night.
4 1,10,22 * */USR/LOCAL/ETC/RC.D/LIGHTTPD restart
The above example represents the 4:45 reboot of Apache for 1, 10, and 22nd per month.
1 * * 6,0/USR/LOCAL/ETC/RC.D/LIGHTTPD restart
The above example shows the 1:10 reboot of Apache every Saturday and Sunday.
0,30 18-23 * * * */usr/local/etc/rc.d/lighttpd restart
The example above shows that Apache is restarted every 30 minutes from 18:00 to 23:00 every day.
0 * * 6/USR/LOCAL/ETC/RC.D/LIGHTTPD restart
The above example indicates that 11:00 PM restarts Apache every Saturday.
* */1 * * * */usr/local/etc/rc.d/lighttpd restart
Restart Apache every hour
* 23-7/1 * * * */usr/local/etc/rc.d/lighttpd restart
From 11 o'clock to 7 in the morning, restart Apache every hour.
0 4 * mon-wed/usr/local/etc/rc.d/lighttpd restart
4th per month with 11 points per Monday to Wednesday restart Apache
0 4 1/USR/LOCAL/ETC/RC.D/LIGHTTPD * Restart
Restart Apache at 4 o ' January 1.
Name: crontab
Use Rights: All users
How to use:
crontab file [-u user]-replaces the current crontab with the specified files.
Crontab-[-u user]-replaces the current crontab with standard input.
crontab-1[user]-lists the user's current crontab.
crontab-e[user]-Edit user's current crontab.
crontab-d[user]-deletes the user's current crontab.
Crontab-c dir-Specifies the directory for crontab.
crontab file format: M H d M D cmd.
M: Minutes (0-59).
H: Hours (0-23).
D: Days (1-31).
M: Month (1-12).
D: Days of the week (0~6,0 for Sunday).
CMD to run the program, the program was sent to SH execution, this shell only user,home,shell these three environment variables
Description
Crontab is used to allow the user to execute a program at a fixed time or at a fixed interval, in other words, a user-like schedule. -u user refers to the setting specified
User's time table, the premise is that you have to have permission (for example, root) to specify other people's schedule. If you do not use-u user, it means that you set the
Set your own schedule.
Parameters:
CRONTAB-E: Execute the text editor to set the schedule, the default text editor is VI, if you want to use another text editor, please set the VISUAL environment variables
To specify the use of that text editor (for example, Setenv VISUAL Joe)
Crontab-r: Deletes the current schedule table
Crontab-l: List the current schedule
crontab file [-u user]-replaces the current crontab with the specified files.
The format of the schedule table is as follows:
F1 F2 F3 f4 f5 program
Where F1 is the minute, F2 represents the Hour, F3 represents the day of the month, the F4 represents the month, and the F5 represents the day of the one week. program says to hold
Line of the program.
When F1 is *, it means that the PROGRAM,F2 is executed every minute for *, and the rest of the program is executed every hour.
When F1 is a-b to be executed from the time of the first a minute to the B minute, the F2 is a-b to be performed from A to a B-hour, and the remainder of the analogy
When F1 is */n, it is executed once every n minutes, F2 is performed once per N-hour intervals for */n, and the rest
When F1 is a, B, C,... The first A, B, C,... Minutes to execute, F2 for a, B, C,... The first is a, B, c ... An hour to execute, and the rest of the analogy
The user can also store all the settings in the file file, using crontab file to set the schedule.
Example:
#每天早上7点执行一次/bin/ls:
0 7 * * */BIN/LS
In December, every day at 6 to 12, every 3 hours of the morning/usr/bin/backup are performed:
0 6-12/3 */usr/bin/backup
Send a letter to Alex@domain.name from Monday to Friday every 5:00:
0 * * 1-5 mail-s "HI" alex@domain.name
Every month at midnight 0:20, 2:20, 4:20 .... Execute echo "haha"
0-23/2 * * * echo "haha"
Attention:
When the program is executed at the time you specify, the system will send you a letter showing the execution of the program, and if you do not wish to receive such a letter, please leave a blank space in each line
After adding >/dev/null 2>&1
Example 2:
#每天早上6点10分
6 * * * Date
#每两个小时
0 */2 * * * Date
#晚上11点到早上8点之间每两个小时, 8 in the morning.
0 23-7/2,8 * * * Date
#每个月的4号和每个礼拜的礼拜一到礼拜三的早上11点
0 4 * mon-wed date
#1月份日早上4点
0 4 1, * date
Example
$crontab-L lists the user's current crontab.