Cron jobs worth setting up on a small website: seven ideas that save time

A cron job is for anything you would otherwise repeat by hand at the same time every day or week: taking a copy of the database, deleting temporary files, importing a price list, sending a summary by e-mail. If you already know how to create one, here are seven concrete uses for a small site on shared hosting. To create one, see cron jobs: what they are for and how to create one.

Seven ideas, most useful first

1	A database copy every night. A `mysqldump` into a folder outside `public_html`, named after the day. It is your insurance against a mistake of yours or a plugin’s. The steps are in automatic backups with cron and mysqldump.

2	Clearing out old files. Exports, temporary files and old copies fill the space without anyone noticing. For example, `find /home/ACCOUNT/exports -type f -mtime +7 -delete` removes whatever is older than seven days. Run it first with `-print` in place of `-delete` to see what would go.

3	Replacing the WordPress scheduler with a real cron job. Scheduled posts go out on time even with no visitors. See swapping WP-Cron for a real server cron job.

4	Calling an address on your own site. Many applications ship a file made for this, such as `/usr/bin/curl -s "https://asuaempresa.co.mz/cron.php?key=SECRET" >/dev/null 2>&1`. Put a key in the address, or anyone can call it.

5	Importing data from outside. A price or stock list a supplier drops every night, read by a PHP script. See running a PHP script from a cron job.

6	Sending a report. Today’s orders, enquiries received, space used. See a scheduled report by e-mail.

7	Warning you when something fails. A script that checks a page or a file and sends a notice. See getting an alert when your site goes down.

How often, and where to see the result

Job	A reasonable frequency	Where you see it ran
Database copy	Once a day, in the small hours.	The new file in the backup folder.
Clearing files	Once a day or once a week.	A smaller folder; use `>>` for a log.
WordPress cron	Every five minutes.	A scheduled post that goes out on time.
Importing data	When the supplier updates, plus a margin.	The modification date of the file or table.
E-mail report	Once a day or once a week.	The e-mail in your inbox.

A cron job spends your account’s resources like a visitor does. Do not schedule anything every minute unless you must: if one run takes longer than the interval they start piling up. The reasoning is in cron jobs.

Keep scripts outside public_html, in a folder such as /home/ACCOUNT/scripts. Nobody can open them from a browser, and they stop depending on the site’s address. Add >> /home/ACCOUNT/cron.log 2>&1 to the end of the line for the first weeks, so you have a record of what happened.

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Where to see it in your account

Your cron jobs run inside your account, under the same limits as the rest of the site. The Cron Jobs page in cPanel lists what is scheduled and when. To know whether a job ran into a limit, open Resource Usage: it shows CPU, memory, entry processes and I/O against the limits of your account, and when the ceiling was reached. A job that goes past those limits can be slowed down or stopped, so it is better to split long jobs into short parts or, for heavy work, move them to a VPS, which gives you full SSH access. For the exact figures that apply to your account, read them on those screens or ask us.

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