Linux VPS Planning Task crond command usage sharing _linux

First, the Installation plan task
This program may not be pre-installed on some systems, and you will need to perform the following command to install it.

Yum Install-y Vixie-cron

Then start the service

Service Crond Start

Second, set up scheduled Tasks
(1) Execute the following command to set up a scheduled task:

Crontab-e

The reason to use the above command instead of using VI directly is because Cron has a few but very necessary syntax checks.
(2) Set the specification of the scheduled task:
T1 T2 T3 T4 T5 Program

T1 represents minutes,
T2 says the hour,
T3 represents the day ordinal of a month,
T4 represents the month,
T5 represents the first day of the one week.
Program represents the programs to be executed.
(3) Some examples:
Perform a/bin/ls every 0 minutes per day of the month:

0 * * * */BIN/LS

In December, every 6 to 12 o ' Day in the morning, every 20 minutes to perform a/usr/bin/backup:

*/20 6-12 */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 </tmp/maildata

Every day at midnight 0:20, 2:20, 4:20 ... execute echo "haha"

0-23/2 * * * echo "haha"

Every two hours between 11 o'clock and 8 in the morning, and at eight a.m. in the morning, executes the date command.

0 23-7/2,8 * * * Date