Linux uses crontab to implement PHP execution plan scheduled tasks_PHP tutorial

First, let’s talk about cron, which is a scheduled execution tool under Linux. Users other than root can use the crontab tool to configure cron tasks. All user-defined crontabs are saved in the /var/spool/cron directory and executed using the identity of the user who created them. To create a crontab entry as a user, log in as that user, and then type the crontab -e command to edit the user's crontab. This file uses the same format as /etc/crontab. When the changes to the crontab are saved, the crontab file is saved according to the username and written to the file /var/spool/cron/username. The cron daemon checks the /etc/crontab file, etc/cron.d/ directory, and /var/spool/cron directory for changes every minute. If changes are found, they are loaded into memory. This way, you don't have to restart the daemon when a crontab file changes.

Install crontab:

yum install crontabs

Instructions:
/sbin/service crond start //Start the service
/sbin/service crond stop //Close the service
/sbin/service crond restart //Restart the service
/sbin/ service crond reload //Reload configuration

View crontab service status: service crond status

Manually start the crontab service: service crond start

Check whether the crontab service has been set to start at boot, execute the command: ntsysv

Add automatic startup at boot:
chkconfig –level 35 crond on

crontab command:

Function description: Set timer.

Syntax: crontab [-u ][configuration file] or crontab [-u ][-elr]

Additional explanation: cron is a resident service that provides a timer function, allowing users to execute preset instructions or programs at a specific time. As long as the user can edit the timer configuration file, the timer function can be used. The configuration file format is as follows:
Minute Hour Day Month DayOFWeek Command

Parameters:
-e Edit the timer settings for this user.
-l List the timer settings for this user.
-r Delete the timer settings for this user.
-u Specifies the user name to set the timer.

crontab format:

Basic format:

Minutes Hours Days Months Weeks Commands

*                                                    

The first column represents minutes 1 to 59. Each minute is represented by * or */1

The second column represents hours 1 to 23 (0 represents 0 o'clock)
The third column represents dates 1 to 31
The 4th column represents the month 1~12
The 5th column identifies the week 0~6 (0 means Sunday)
The 6th column represents the command to be run

Remember the meanings of several special symbols:

“*” represents a number within the value range,
“/” represents “every”,
“-” represents from a certain number to a certain numbers,
"," separates several discrete numbers

# Use the hash sign to prefix a comment

# +————- minute (0 – 59)
# | +————- hour (0 – 23)
# | | +——- day of month (1 – 31)
# | | | +——- month (1 – 12)
# | | | | +——- day of week (0 – 7 ) (Sunday=0 or 7)
# | | | | |
# * * * * * command to be executed

A few examples of crontab are as follows:

(1) First example.

30 21 * * * /etc/init.d/nginx restart

Restart nginx at 21:30 every night.

(2) The second example, which is the example tested in this tutorial

* * * * * /usr/bin/php -f /root/test.php >> test.log

Execute the /root/test.php file every minute and output the results to test.log.

After completing the above basic work, let’s take a look at how to use crontab to execute PHP scripts regularly:

(1) I created a new test.php file under /root with the following content:

Note: You can use whereis php to find the location of the php execution file.

(2) Then crontab -e writes the following shell: