Cron jobs are a way of automating tasks that you want done every week/month/day and at a certain time. To accomplish this, you will make crontab entries on your server which will tell it when it needs to run the command you want. Crontab entries tell the server to "run this command at this time on this date". Using cron with LinkX will allow you to have the software backup the database and run the link scanner at times you specify.
Crontab Entries
A crontab entry consists of two parts - a time to run, and a command to run.
The time to run (the first part of the entry) is broken up into 5 fields:
1. minute of the hour
2. hour of the day (on the 24 hour clock)
3. day of the month
4. month of the year (1 = January, 2 = February, etc.)
5. day of the week (0 = Sunday, 1 = Monday, 2 = Tuesday, ..., 6 = Saturday)
A * in one of these fields indicates that the job should be executed at any or every one of these, so for instance a * in the month of the year field means that this task should be carried out every month at the time specified in the other fields. A * in the day of the week field, when there is something in the day of the month field, does not mean that this task should be carried out every day, but rather that it should be carried out on the appointed day of the month regardless of what weekday it is. Only *s in the day of the week field, and the day of the month field, and the month of the year field would indicate a daily task.
Examples:
In the examples, [command] represents the full path and filename of the file you want to execute.
The job with this time to run would run every Sunday at 12:20 am:
20 0 * * 0 [command]
This job would run at midnight on any Friday the 13th:
0 0 13 * 5 [command]
You don't have to put just one time in a field. This job, for instance, would run every day at 12:30am, 2:30am, 4:30am, 6:30am, 6:30pm, 8:30pm, and 10:30pm:
30 0,2,4,6,18,20,22 * * * [command]
This one would run every Tuesday and Friday at 5:30 am:
30 5 * * 2,5 [command]
Creating a File For Crontab Entries
To register the cron commands with the server, you will need to create a plain text file with a list of all of the crontab entries. You will then use this file along with the server's crontab command to register them with the server. Once they have been registered, they can begin executing at the time you specify.
Start with an empty text file in the text editor of your preference (we recommend EditPlus for Windows users). At the top of this file you will want to put any already existing crontab entries that you have running on your server. If you have never used cron before, there will not be any. If you have used cron before, you will need to login to your server through telnet or SSH and execute the crontab -l command. This will display a list of your existing crontab entries. Copy and paste this to the top of your text file.
Now you can start adding your LinkX crontab entries to the file. All of the available commands are covered later in this document, so be sure to read the entire thing before setting up your cron jobs.
Once you have all of the above steps completed, you can save the file. You can name it anything you want. It is recommended that you use cron.txt for the filename, however anything will work. To register these commands with the server, continue with the next section of this document.
Here is an example crontab entry file for you to look at.
Registering Your Cron Commands
Once you have created the text file containing your crontab entries, you will need to register them with the server. To do this, upload the text file to your server (for this example, assume the filename is cron.txt). A good place to upload it is the same directory where LinkX is installed.
After the cron.txt file has been uploaded, login to your server through telnet or SSH. Change into the directory where you uploaded the cron.txt file and run the command crontab cron.txt. This will register the crontab entries with the system, and they will begin executing at the next scheduled time. To make sure your crontab entries were recorded properly, you can run the crontab -l command. This will display a list of all of the current crontab entries registered under your username.
Using the cron.php Script
To use the cron.php script your server will need to have the command line interface (CLI) version of PHP installed. If you are not sure about this, contact your server administrator and ask them if the CLI version of PHP is installed on the server. You will also need to know where the CLI PHP binary is located on the server. In most cases it is in /usr/bin or /usr/local/bin
The cron.php script will accept a command line argument that will tell it which function it should run. Each of the available command line arguments are listed below.
-
--backup - This will backup your member database.
0 0 * * * /path/to/php /full/directory/path/to/cron.php --backup data.txt
Note that the /full/directory/path/to/ portion would be replaced with the directory path on your server to the directory where the cron.php script is located and /path/to/php would be replaced with the location of the CLI version of PHP on your server. The data.txt portion of the command specifies the filename to use for the database backup. This file will be created in the data directory of your LinkX installation and will contain all of the database information.
Using the scanner.php Script
To use the scanner.php script your server will need to have the command line interface (CLI) version of PHP installed. If you are not sure about this, contact your server administrator and ask them if the CLI version of PHP is installed on the server. You will also need to know where the CLI PHP binary is located on the server. In most cases it is in /usr/bin or /usr/local/bin
You can start the scanner.php script through cron to have your links automatically scanned at the times you specify. The scanner.php script will need to be passed the ID number of the scanner configuration you want it to run. You can find the ID number for each configuration next to it's Identifier in the control panel interface. For example, if you wanted to run the link scanner with configuration id 7 once every week at 6am on Sunday, you would use the following crontab entry:
0 6 * * 0 /path/to/php /full/directory/path/to/scanner.php 7 &
Note that the /full/directory/path/to/ portion would be replaced with the directory path on your server to the directory where the scanner.php script is located and /path/to/php would be replaced with the location of the CLI version of PHP on your server.