Cron jobs and random times, within given hours

Question

I need the ability to run a PHP script 20 times a day at completely random times. I also want it to run only between 9am - 11pm.

I\'m familiar with creating cron job

Answer 1

al-x 's Solution does not work for me since crontab commands are not executed in bash but in sh I guess. What does work is:

30 8 * * * bash -c "sleep $[RANDOM\%90]m" ; /path/to/script.py