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

at -f [file] [timespec]

or

echo [command] | at [timespec]

or

at [timespec] ... and interactive specification like script's recording.

Command

At runs the text provide on stdin or in the file specified by -f [file].

Timespec

Here's the [timespec] grammar. It can be something like:

• 24-hour time as 4-digit int, e.g. 0100, 2359, 1620
• now + 10 minutes
• 2071-05-31 - 5 hours 12 minutes UTC

If you're explicitly specifying the timezone, some versions of the timespec might only allow UTC for the optional timezone argument.

Example

cat script.sh | at now + $(($RANDOM % 10)) hours $(($RANDOM % 60)) minutes

at -f script.sh now + $(($RANDOM % 10)) hours $(($RANDOM % 60)) minutes

Try it out...

You can test the bash parsing by pre-pending echo and escaping the | (pipe).

echo cat script.sh \| at now + $(($RANDOM % 10)) hours $(($RANDOM % 60)) minutes

echo at -f script.sh now + $(($RANDOM % 10)) hours $(($RANDOM % 60)) minutes

To see jobs scheduled, use atq and job contents (environment vars, setup, and command/script) with at -c [jobid].

Note

The system is part of cron, and the interactive prompt actually captures the whole current state of your shell, so you can run commands without specifying absolute paths.