Is there a way to run a shell script on a custom cron?

Question

I'm new to all this so maybe this isn't the best solution, but I've created a shell script cache warmer.

wget --quiet http://www.example.com/custom-sitemap.xml --output-document - |
egrep -o "http://www.example.com/[^<]+" | wget --delete-after -i -

I can also do this with drush commands too using the cache warmer module.

I need to figure out how to run these commands every couple of hours.

My understanding was that I could create a custom cron job with Elysia cron that ran the script on my server, but now I am confused if this is possible / how to implement.

When I go to the script section and write the following:

*/15 * * * * custom_cron

I am told it it is an invalid line.

Can you make custom timed cron jobs then use the elysia cron API to make a module call my shell script?

Thanks!

Answer 1

I believe you can edit the crontab or by talking to hosting provider you will be able to edit the crontab file.

In case, if you have to do it in custom module using Elysia Cron API, I assume you can do it following way :

function example_cronapi($op, $job = NULL) {
  $items['example_shell_cron'] = array(
    'description' => 'Send mail with news',
    'rule' => '0 */4 * * *', // Every 4 hours
  );
  return $items;
}


function example_shell_cron() {
  shell_exec ('wget --quiet http://www.example.com/custom-sitemap.xml --output-document - |
egrep -o "http://www.example.com/[^<]+" | wget --delete-after -i -');
}

Answer 2

The documentation under Linux for crontab is found in a manual page:

man 5 crontab

The 5 is important to indicate the section you want to see (section 1 shows you the command line documentation.)

Cron runs from / in most cases, so it won't find a script as you specified it. You have two solutions: make sure it can run from a specific user, which should be the case for root, or place the script somewhere under /var/... or /etc/... Then change the crontab script to use a full path:

*/15 * * * * /home/my_user_name/custom_cron

Using crontab you can also defined variables. Also remember that you do not have the full environment loaded. Your script needs to do that if you need a full environment.

Another way, assuming you don't need to run it every 15 minutes, is to place the script under a cron directory in /etc. In my case I use cron.hourly.

This means no setup in crontab, just copy the script under that directory, probably with a filename that makes sense such as:

/etc/cron.hourly/drupal.sh

That .sh file must be executable (have the x flag set) as in chmod 755 /etc/cron.hourly/drupal.sh.