Linux program crontab

In linux, crontab is used to start the crontab service. Generally, the/sbin/service crond start is used to start the cron service of the root user. You can use the sudo service crond start to check whether the service is running. Use ps-ax | grep cron. check whether the crontab service under this user is successfully created, use crontab-l to list a user's cron service crontab-l //-l to list a user's task plans to delete a user's cron service crontab-r //-r to delete a user's task edit a user's cron service crontab-e //-e edit a user's task specify a user's cron service crontab-u //-u specify the location where a user's crontab files are stored/ syntax of the cron file of the corresponding user in etc/crontab/var/spool/cron: "*" indicates a number in the value range, "/" indicates "every", and "-" indicates that a number is transferred to a number. "," separates several discrete numbers, for unspecified fields, use "*" to fill the value of the command 0-59 0-23 1-31 1-12 0-6 command (value range, 0 indicates that a normal line of Sunday corresponds to a task.) 3 3 3 3 3 3 * ls (execute the ls command at on July 10, March 3 every year) 3 3, 13 3-8 * ls (execute the ls command from 3 to 3 and 3 and 3 and 3 to 03 of 13 every year) */3 3, 13 3-8 * ls (execute the ls command every 3 minutes from 3 to 3, And, January 1, August)