Scheduled task execution commands in Linux

In Linux, after the scheduled task execution command has the mail alarm function, the next step is to make a scheduled task for periodic execution of this task, in this way, you can receive the alarm information periodically. Before doing a scheduled task, check the current system time [date "+ % Y-% m-% d % T"] and hardware clock time [hwclock ]: [root @ localhost test] # date "+ % Y-% m-% d % T" 2013-07-01 07:57:52 [root @ localhost test] # hwclock on Monday 1, July 01, 2013-48 seconds- 0.059059 the results above seconds show that, my current clock time is incorrect. Set the system time first: [root @ localhost test] # date-s "July 09, 2013 08:47:00" 08:47:00 CST reset hardware time and system time synchronization [root @ localhost test] # hwclock-w next to view system time and hardware clock time: [root @ localhost test] # hwcl Ock 08:47:13-0.180411 seconds [root @ localhost test] # date "+ % Y-% m-% d % T" July 09, 2013 [root @ localhost test] # The time is normal, now we can do the scheduled task. In Linux, it is relatively simple to do the scheduled task. You can use the crontab command. Edit a test. sh. The content is formatted to display the current system time: date "+ % Y-% m-% d % T". Run the following command to view the result: [zl @ localhost test] $ sh test. sh2013-07-09 09:03:28 good, the result is normal. The following is a brief introduction to the crontab command: common parameters: crontab-l // view the cron task crontab-e under the current user // edit the current user's scheduled task [zl @ localhost test] $ crontab-l52 8 *** sh/home /zl/test. sh>/home/zl/test/test_chrontab.txt indicates that my current user has a scheduled task. Let's analyze this scheduled task: 52 8 *** sh/home/zl/test. sh> The/home/zl/test/test_chrontab.txt task is divided into six parts, abstracted as the hour, month, and week command ***** command column 1st indicates minute 1 ~ 59 every minute, use * or */1 to indicate 2nd columns to indicate hour 1 ~ 23 (0 indicates 0 points) column 3rd indicates date 1 ~ 31 column 4th indicates the month 1 ~ 12 column ID No. 0 ~ 6 (0 indicates Sunday). For example, run the preceding command in the 6th column. The task is executed at 08:52 every day and the command is sh/home/zl/test. sh>/home/zl/test/test_chrontab.txt if we need to add another weekly report task at every Friday, then run crontab-e [run the text editor to set the time table, and the preset text editor is vi]. Add 50 23 ** 5 sh/home/zl/weekly_report.sh to the task: [zl @ localhost test] $ crontab-ecrontab: installing new crontab: view the task list again, A new task [zl @ localhost test] $ crontab-l52 8 *** sh/home/zl/test is added. sh>/home/zl/test/tes T_chrontab.txt50 23 ** 5 sh/home/zl/weekly_report.sh [zl @ localhost test] $ here are some examples used by others: 0 21 ***/usr/local/etc/rc. d/lighttpd restart the above example indicates restarting apache at every night. 45 4, 22 **/usr/local/etc/rc. d/lighttpd restart the preceding example indicates restart apache on 4: 45 every month on day 1, 10, and 22. 10 1 ** 6, 0/usr/local/etc/rc. d/lighttpd restart the example above indicates that apache is restarted at every Saturday and Sunday. The preceding example of-23 ***/usr/local/etc/rc. d/lighttpd restart indicates that apache is restarted every 30 minutes from to every day. 0 23 ** 6/usr/local/etc/rc. d/lighttpd restart the preceding example indicates that apache is restarted at every Saturday. **/1 ***/usr/local/etc/rc. d/lighttpd restart apache * 23-7/1 */usr/local/etc/rc every hour. d/lighttpd restart: restart apache 0 11 4 * mon-wed/usr/local/etc/rc every hour from. d/lighttpd restart: restart apache 0 4 1 jan */usr/local/etc/rc from every Monday to Wednesday. d/lighttpd restart apache at on January 1, January 1