Cron can run simple commands, shell scripts, and programs written in languages such as PHP, Python, and Perl. If a task can be completed on the command line or in a script, you can automate it with the task scheduler.<\/p>\n\n\n\n
Cron job use-cases include<\/strong>:<\/strong><\/h2>\n\n\n\n- Log rotation<\/strong> \u2014 rotate old logs to an archive at pre-set intervals to stop them from growing to an unmanageable size.<\/li>
- Emailing users<\/strong> \u2014 alert users when they\u2019re approaching resource limits.<\/li>
- Triggering updates<\/strong> \u2014 schedule checks for security updates and apply them automatically.<\/li>
- Content management system and database backups<\/strong> \u2014 ensure you never forget to complete essential backups.<\/li><\/ul>\n\n\n\n
Configuring a Cron Job in cPanel<\/strong><\/h2>\n\n\n\nCron uses a compact notation to represent times and days. A typical configuration line might look like this:<\/p>\n\n\n\n
30 23 25 * * myscript.sh<\/p>\n\n\n\n
The format has five white-space separated fields for time intervals followed by a command. <\/p>\n\n\n\n
The schedule is stored in a \u201ccrontab\u201d file, a list of jobs with additional directives. You can edit the file over SSH with the crontab<\/em> command, but using cPanel & WHM is faster, easier, including two interfaces for scheduling jobs: one for cPanel\u2019s maintenance scripts and one for user scripts, which we\u2019ll take a look at in the next section. <\/p>\n\n\n\nBefore we get to cPanel\u2019s cron configuration interface, you should have a firm grasp of the interval notation. <\/p>\n\n\n\n
The time fields represent the following, from left to right:<\/p>\n\n\n\n
- Minutes<\/strong> \u2014 a number between 0 and 59.<\/li>
- Hours<\/strong> \u2014 a number between 0 and 23. Cron uses the 24-hour format, so 4 p.m is 16, 11 p.m. is 23, and so on. <\/li>
- Days of the month<\/strong> \u2014 a number between 1 and 31.<\/li>
- Months<\/strong> \u2014 a number between 1 and 12.<\/li>
- Days of the week<\/strong> \u2014 a number between 0 and 7, with Sunday represented as either 0 or 7.<\/li><\/ul>\n\n\n\n
Fields with an asterisk indicate that the job will run at every relevant interval compatible with the other fields.<\/p>\n\n\n\n
Our first example specified the time interval \u201c30 23 25 * *\u201d. This is the 30th minute of the 23rd hour of the 25th day of the month. Or, to put it another way, 11:30 in the evening on the 25th of each month. Because the Month and Day of Week fields contain asterisks, the script runs on days and months for which the other fields are valid; in this case, every day and month. <\/p>\n\n\n\n
Let\u2019s look at some more complex examples. You have a monitoring script that you would like to run every hour, on the hour, between 9 a.m and 5 p.m., but only on weekdays. To achieve this, we have to introduce another piece of notation, the range.<\/p>\n\n\n\n
00 9-17 * * 1-5 myscript.sh<\/p>\n\n\n\n
Ranges are values separated by a hyphen. The example breaks down as:<\/p>\n\n\n\n
- 00 \u2014 the first (or, more accurately, the zeroeth) minute of the hour. <\/li>
- 9-17 \u2014 each hour between 9 a.m and 5 p.m.<\/li>
- * \u2014 every day.<\/li>
- * \u2014 every month.<\/li>
- 1-5 \u2014 the first to the fifth day, so Monday to Friday. <\/li><\/ul>\n\n\n\n
What if, instead of every hour between 9 a.m. and 5 p.m, you wanted the script to run at 9 a.m, 12 p.m., 3 p.m., and 6 p.m on weekdays. For intervals of this type, you need one more piece of notation, the list. <\/p>\n\n\n\n
00 9,12,15,18 * * 1-5 myscript<\/p>\n\n\n\n
This example is the same as the previous one, but with a list in the Hours field instead of a range. <\/p>\n\n\n\n
The basics we have outlined here should cover almost every situation, but cron has an incredibly flexible notation with additional shortcuts and directives. If you want to learn more, take a look at this article<\/a> or the man page on your CentOS server with the command \u201cman 5 crontab.\u201d<\/p>\n\n\n\nConfiguring cPanel Cron Jobs in WHM<\/strong><\/h3>\n\n\n\n
Configuring a Cron Job in cPanel<\/strong><\/h2>\n\n\n\nCron uses a compact notation to represent times and days. A typical configuration line might look like this:<\/p>\n\n\n\n
30 23 25 * * myscript.sh<\/p>\n\n\n\n
The format has five white-space separated fields for time intervals followed by a command. <\/p>\n\n\n\n
The schedule is stored in a \u201ccrontab\u201d file, a list of jobs with additional directives. You can edit the file over SSH with the crontab<\/em> command, but using cPanel & WHM is faster, easier, including two interfaces for scheduling jobs: one for cPanel\u2019s maintenance scripts and one for user scripts, which we\u2019ll take a look at in the next section. <\/p>\n\n\n\nBefore we get to cPanel\u2019s cron configuration interface, you should have a firm grasp of the interval notation. <\/p>\n\n\n\n
The time fields represent the following, from left to right:<\/p>\n\n\n\n
- Minutes<\/strong> \u2014 a number between 0 and 59.<\/li>
- Hours<\/strong> \u2014 a number between 0 and 23. Cron uses the 24-hour format, so 4 p.m is 16, 11 p.m. is 23, and so on. <\/li>
- Days of the month<\/strong> \u2014 a number between 1 and 31.<\/li>
- Months<\/strong> \u2014 a number between 1 and 12.<\/li>
- Days of the week<\/strong> \u2014 a number between 0 and 7, with Sunday represented as either 0 or 7.<\/li><\/ul>\n\n\n\n
Fields with an asterisk indicate that the job will run at every relevant interval compatible with the other fields.<\/p>\n\n\n\n
Our first example specified the time interval \u201c30 23 25 * *\u201d. This is the 30th minute of the 23rd hour of the 25th day of the month. Or, to put it another way, 11:30 in the evening on the 25th of each month. Because the Month and Day of Week fields contain asterisks, the script runs on days and months for which the other fields are valid; in this case, every day and month. <\/p>\n\n\n\n
Let\u2019s look at some more complex examples. You have a monitoring script that you would like to run every hour, on the hour, between 9 a.m and 5 p.m., but only on weekdays. To achieve this, we have to introduce another piece of notation, the range.<\/p>\n\n\n\n
00 9-17 * * 1-5 myscript.sh<\/p>\n\n\n\n
Ranges are values separated by a hyphen. The example breaks down as:<\/p>\n\n\n\n
- 00 \u2014 the first (or, more accurately, the zeroeth) minute of the hour. <\/li>
- 9-17 \u2014 each hour between 9 a.m and 5 p.m.<\/li>
- * \u2014 every day.<\/li>
- * \u2014 every month.<\/li>
- 1-5 \u2014 the first to the fifth day, so Monday to Friday. <\/li><\/ul>\n\n\n\n
What if, instead of every hour between 9 a.m. and 5 p.m, you wanted the script to run at 9 a.m, 12 p.m., 3 p.m., and 6 p.m on weekdays. For intervals of this type, you need one more piece of notation, the list. <\/p>\n\n\n\n
00 9,12,15,18 * * 1-5 myscript<\/p>\n\n\n\n
This example is the same as the previous one, but with a list in the Hours field instead of a range. <\/p>\n\n\n\n
The basics we have outlined here should cover almost every situation, but cron has an incredibly flexible notation with additional shortcuts and directives. If you want to learn more, take a look at this article<\/a> or the man page on your CentOS server with the command \u201cman 5 crontab.\u201d<\/p>\n\n\n\nConfiguring cPanel Cron Jobs in WHM<\/strong><\/h3>\n\n\n\n
Before we get to cPanel\u2019s cron configuration interface, you should have a firm grasp of the interval notation. <\/p>\n\n\n\n
The time fields represent the following, from left to right:<\/p>\n\n\n\n
- Minutes<\/strong> \u2014 a number between 0 and 59.<\/li>
- Hours<\/strong> \u2014 a number between 0 and 23. Cron uses the 24-hour format, so 4 p.m is 16, 11 p.m. is 23, and so on. <\/li>
- Days of the month<\/strong> \u2014 a number between 1 and 31.<\/li>
- Months<\/strong> \u2014 a number between 1 and 12.<\/li>
- Days of the week<\/strong> \u2014 a number between 0 and 7, with Sunday represented as either 0 or 7.<\/li><\/ul>\n\n\n\n
Fields with an asterisk indicate that the job will run at every relevant interval compatible with the other fields.<\/p>\n\n\n\n
Our first example specified the time interval \u201c30 23 25 * *\u201d. This is the 30th minute of the 23rd hour of the 25th day of the month. Or, to put it another way, 11:30 in the evening on the 25th of each month. Because the Month and Day of Week fields contain asterisks, the script runs on days and months for which the other fields are valid; in this case, every day and month. <\/p>\n\n\n\n
Let\u2019s look at some more complex examples. You have a monitoring script that you would like to run every hour, on the hour, between 9 a.m and 5 p.m., but only on weekdays. To achieve this, we have to introduce another piece of notation, the range.<\/p>\n\n\n\n
00 9-17 * * 1-5 myscript.sh<\/p>\n\n\n\n
Ranges are values separated by a hyphen. The example breaks down as:<\/p>\n\n\n\n
- 00 \u2014 the first (or, more accurately, the zeroeth) minute of the hour. <\/li>
- 9-17 \u2014 each hour between 9 a.m and 5 p.m.<\/li>
- * \u2014 every day.<\/li>
- * \u2014 every month.<\/li>
- 1-5 \u2014 the first to the fifth day, so Monday to Friday. <\/li><\/ul>\n\n\n\n
What if, instead of every hour between 9 a.m. and 5 p.m, you wanted the script to run at 9 a.m, 12 p.m., 3 p.m., and 6 p.m on weekdays. For intervals of this type, you need one more piece of notation, the list. <\/p>\n\n\n\n
00 9,12,15,18 * * 1-5 myscript<\/p>\n\n\n\n
This example is the same as the previous one, but with a list in the Hours field instead of a range. <\/p>\n\n\n\n
The basics we have outlined here should cover almost every situation, but cron has an incredibly flexible notation with additional shortcuts and directives. If you want to learn more, take a look at this article<\/a> or the man page on your CentOS server with the command \u201cman 5 crontab.\u201d<\/p>\n\n\n\n
Configuring cPanel Cron Jobs in WHM<\/strong><\/h3>\n\n\n\n
- Hours<\/strong> \u2014 a number between 0 and 23. Cron uses the 24-hour format, so 4 p.m is 16, 11 p.m. is 23, and so on. <\/li>