Cron is service designed to execute a specified command in a scheduled time.
The shhedule is supposed to be edited with command
and can be viewed with command
Cron can be used to handle sites that do not show history of their revisions.
Cron can be used to detect moment, when the publication disappears from its original site.
https://en.wikipedia.org/wiki/Cron The software utility cron is a time-based job scheduler in Unix-like computer operating systems. Users that set up and maintain software environments use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, dates, or intervals. It typically automates system maintenance or administration—though its general-purpose nature makes it useful for things like downloading files from the Internet and downloading email at regular intervals. The origin of the name cron is from the Greek word for time, χρόνος (chronos).//
Cron is most suitable for scheduling repetitive tasks. Scheduling one-time tasks can be accomplished using the associated at utility.
# ┌── minute (0 - 59) # │ ┌── hour (0 - 23) # │ │ ┌── day of the month (1 - 31) # │ │ │ ┌───── month (1 - 12) # │ │ │ │ ┌───── day of the week (0 - 6) (Sunday to Saturday; # │ │ │ │ │ 7 is also Sunday on some systems) # │ │ │ │ │ # │ │ │ │ │ # * * * * * <command to execute>
https://crontab.guru crontab guru. The quick and simple editor for cron schedule expressions by Cronitor