Run a Cron at Specific time.

jrahma

Hi,

I have cron job on my host at San Diago. The job will run every day at midnight (san diago time of course). But my time here in Bahrain is GMT +3.

How can I let my PHP run at midnight (Bahrain time)?

Thanks,
Jassim

schwim

If you don't have the ability to manage your cron jobs, you can ask your host to change the cron job to run at 2:pm PST. There's nothing magic to a cron job, there can be as many as you'd like and they are highly configurable.

jrahma

but isn't it possible to configure the time in PHP something like convert the EST to GMT+3 while running the cron?

schwim

The crontab is run by the server OS. It has nothing to do with PHP other than the fact that a PHP script can be run via the crontab.

jrahma

My point is when the cron start, can the PHP check which is invoked by the corn check the server timezone and say if the time is EST then if it's 12 (on GMT) then run otherwise ignore.

schwim

You said the cron is set to run at a time you do not want it to run. Therefore, every time the cron runs(once a day at midnight, PST), it will be at a time you do not want your script to run. If you want your script to run at a different time, you have to add another cron job or edit the one that's currently set to run at your desired time.

If it's not critical that it run exactly at your desired time and there's PHP pages that are often accessed(public website with visits), then you can write into your PHP script to run if it's after your desired time and it has yet to run for that day. You'd need to keep record either in a database or file for the last run time, at the very least.

jrahma

I was think if I can run it every hour and let the PHP check if that hour is equal to midnight at my local time

laserlight

jrahma wrote:
I was think if I can run it every hour and let the PHP check if that hour is equal to midnight at my local time

That is possible, but it is a waste. The right approach is to configure the cron job.

schwim

If you can modify your cron to run every hour, why can't you change the time at which the cron job runs?

jrahma

Because the cron is for birthday greeting so anytime i run it will check the date on the server

laserlight

jrahma wrote:
Because the cron is for birthday greeting so anytime i run it will check the date on the server

What's stopping you from setting it to run once a day at midnight (Bahrain time) then?

Bonesnap

To ELI5 what laserlight has suggested you to do:

Find out the timezone where the server is located.
Find out the timezone Bahrain is located (hopefully you know this 😉)
Do some basic math to figure out the difference in hours
Apply this difference to the cron job's schedule
????
PROFIT

For example if local time in Bahrain is 5 hours ahead of where the server is, then set the cron job to run at 7pm. Anytime it's 7pm where the server is, it's midnight in Bahrain.

Your PHP script should not be checking the date or time; you have already determined that by the cron job's schedule.

Hope this helps!

EDIT: It may be possible to set the timezone for the cron job; I just assumed that it ran according to local time only. If you are able to set the timezone then... just do that. 🙂

dalecosp

This is all great advice, and probably apropos for this specific application.

I will however, mention one situation where the OP might have the right idea.

After quite a bit of development on our flagship site, we found we had cronjobs galore. (Over 3 dozen, I think). Cron was "managing" them ... sort of.

You see, cron itself doesn't give a flip whether one job is finished or not when it runs another, as long as it runs it at the proper time.

So, we'd end up with server loads of ungodly numbers when the cronjobs started to grow into long-running processes that were DB-intensive and cron would go ahead and start another job anyway.

Our solution: implement all crons as PHP files. Now our cron file shows 3 jobs: "daily.php", "hourly.php", and "frequent.php".

The scripts check for the presence of a lockfile indicating another cronjob has priority (if so, they sleep a while and check again, up to a max sleep value at which they just give up). When they run, they check what time it is and run the appropriate jobs for that part of the hour (frequent.php), or that hour (hourly.php), or a given day (daily.php).

The server is much happier now. ;-)