What is the minimum and maximum permissible interval for running automatic Cron scripts?

The minimum interval for running Cron scripts is usually 1 minute, as the standard cron syntax does not support more frequent execution (for example, every 30 seconds). There is no maximum time limit — you can set up execution intervals in hours, days, weeks, and even months.

Example of a record to run a script every minute:

* * * * * /usr/bin/php /path/to/script.php

If you need to run at intervals less than a minute, this is usually implemented not through cron, but via daemons or scripts with loops and delays inside.