[PHP] Dynamic cron jobs?

Question

I'm writing a script that needs to be called at a random time during the day, but am not sure how to accomplish this.

I don't want to waste server resources to run a cron job every minute.

I want the script to be called at random, so generating the random times for say a month in advance and then creating cron jobs for each of them isn't what I'm looking for.

Also this script only needs to be executed once a day.

Thanks in advance!

Answer 1

Have each run submit a further run using 'at' with a random time? That wouldn't guarantee it ran every day, but you could get that as an average.

Answer 2

If you have access to it, modify the crontab file whenever your target script runs and add in a random time.

Answer 3

This will add a cron job:

cat "* * * * * /path/to/script" | crontab

You need to generate a proper time instead of * * * * * (it will run every minute otherwise).

cat "* * * * * /path/to/script" | crontab -r

will remove the job. So, now you need to call those from PHP script, I don't remember exactly how it's done in PHP.

EDIT

http://php.net/manual/en/function.system.php

MORE EDIT

Every time script executes, it's two last operations might be removing the current cron job and generating another one for the next day.

EVEN MORE EDIT

http://codepad.org/Z1B2v4lF -- here's how I would do it in Python. This may run more than once a day. If running only once a day is a must, you can add a day-of-month value as well.