我可以从另一个 cron 作业正在执行的 php 脚本中修改 cron 作业的时间表吗？

Question

For example I have a cron running on the 1st of every month, this cron executes a PHP script that returns some dates.

I want to use these dates and modify the schedule of another cron job?

I know I can add a new cronjob doing something like this but unsure of how to update 1 specific entry when there could be multiple.

$output = shell_exec('crontab -l');
file_put_contents('/tmp/crontab.txt', $output.'* * * * * NEW_CRON'.PHP_EOL);
echo exec('crontab /tmp/crontab.txt');

Answer 1

Make sure you do not break something you better monitor your cronjobs after you deploy this 😉 But what you want to do is possible.

1. You can create, modify and delete Cronjobs via PHP ( Use PHP to create, edit and delete crontab jobs? )

2. This is also true if this PHP is executed via another cronjob (as long as you give the correct permissions)

⇒ It is possible (qed)

Also see this question: https://askubuntu.com/questions/408611/how-to-remove-or-delete-single-cron-job-using-linux-command

This is how you remove a single cronjob (by example) - just create a new one for the different dates:

crontab -u mobman -l | grep -v 'perl /home/mobman/test.pl'  | crontab -u mobman -