Linux crontab use

1. Viewing, editing, and deleting

Cron saves the command line in the crontab (cron table) file, which is usually in the/etc directory. Each system user can have their own crontab (under/var/spool/cron/). To view the current user's crontab, enter crontab-l; To edit crontab, enter crontab-e; To delete crontab, enter Crontab-r. If you are currently root, to view/edit/delete/a user's crontab, simply add the-u USERNAME (such as crontab-e-U USERNAME) after the corresponding command. The default editor for the crontab file is VI, and you can enter export visual= ' editor ' to change the default editor. Cron service every minute not only to read all the files in the/var/spool/cron directory, but also to read the/etc/crontab file once. Configuring this file also allows Cron to perform tasks. Using the crontab command is a configuration of a user-level task, and editing a/etc/crontab file is a configuration of a system-level task.

2.Linux Task Start

/sbin/service crond start/sbin/service crond stop/sbin/service crond restart/sbin/service crond reload/sbin/service Crond status

3.cron Time Format

crontab format 1th column minute 1~59 2nd Column hour 1~23 (0 means midnight) 3rd Liege 1~31 4th Column Month 1~12 5th Column Week 0~6 (0 = Sunday) 6th column to run the command below is the format of crontab: Time-sharing day and month Commands to run here are some examples of crontab file entries: * * * * * * * * * * * * * * * * * * * * * * * * * * */usr/local/apache/bin/apachectl Restart above shows the 21:30 restart Apache per night 4 1,10,22 * */usr/local/apache/bin/apachectl Restart the above example shows the 4:45 restart Apache per month for 1, 10, 22nd. 1 * * 6,0/usr/local/apache/bin/apachectl Restart the above example shows that 1:10 restarts Apache every Saturday and Sunday. 0,30 18-23 * * * */usr/local/apache/bin/apachectl Restart the above example shows that Apache restarts every 30 minutes from 18:00 to 23:00 every day. 0 * * 6/usr/local/apache/bin/apachectl Restart the above example indicates that the Apache is restarted every Saturday. * */1 * * * */usr/local/apache/bin/apachectl Restart restart every hour apache* 23-7/1 * */usr/local/apache/bin/apachectl restart 11 o'clock To 7 hours in the morning, restart every hour apache0 4 * mon-wed/usr/local/apache/bin/apachectl Restart monthly 4th and 11 points per Monday to Wednesday restart APACHE0 4 1 Jan */usr/loc Al/apache/bin/apachectl Restart January 1 4-point restart Apache

Linux crontab use