Cron tab tasks are easy to do after you learn the syntax. Until I understood how to schedule tasks with cron, I have googled a lot, every time I needed to do something in cron.
Today, I will show you how to make your task run in all the odd or even days, of a month.
Let’s make a convention. We will use 30 days as the base for the even-days and 31 days for executing in the odd days only. Yes, I know that not all the months in a year have the same number of days. And I also know that there is a February month having 28 or 29 days only, but this may not concert you because the task job will work perfectly and in February will just not match the last 2-3 days.
Type cron -e and copy/paste this (don’t forget to do chmod +x /path/to/script for the script to be executed):
# Will only run on odd days:
0 0 1-31/2 * * /path/to/script
# Will only run on even days:
0 0 0-30/2 * * /path/to/script