Linux – How to setup a cron job every random weekday

bashcentoscronlinuxUbuntu

As the question is fairly self-explanatory, I would like to know how to set a cronjob to execute any random weekday without using any external script.

EDIT: In case people have not understood this question, We have 5 weekdays, viz., Monday, Tuesday, Wednesday, Thursday, Friday. I have a server running 24/7. I want to set a cron that will run on any 1 weekday per week.

Note: I highly doubt this is a duplicate question, as this question is not pertaining to daily/weekly/monthly cronjobs.

Best Answer

Would something like this work for you? It selects a random day from a bash array days (note the SHELL prefix) and then writes a cronjob (random_runner) under /etc/cron.d to run the script /home/foobar/myscript.

You could place this in /etc/cron.d/random_generator and generate a new "runner" every day.

SHELL=/bin/bash
27 8 * * * root  days=(Mon Tue Wed Thu Fri Sat Sun); rd="$(( RANDOM \% 7 ))"; day="${days[$rd]}"; echo "45 15 * * $day root /home/foobar/myscript" > /etc/cron.d/random_runner

Related Solutions

Linux Cron – Can a Cron Job Run More Frequently Than Every Minute?

If your task needs to run that frequently, cron is the wrong tool. Aside from the fact that it simply won't launch jobs that frequently, you also risk some serious problems if the job takes longer to run than the interval between launches. Rewrite your task to daemonize and run persistently, then launch it from cron if necessary (while making sure that it won't relaunch if it's already running).

Cron Job – How to Run a Cron Job Manually and Immediately

Here's what I did, and it seems to work in this situation. At least, it shows me an error, whereas running from the command line as the user doesn't show the error.

Step 1: I put this line temporarily in the user's crontab:

* * * * *   /usr/bin/env > /home/username/tmp/cron-env

then took it out once the file was written.

Step 2: Made myself a little run-as-cron bash script containing:

#!/bin/bash
/usr/bin/env -i $(cat /home/username/tmp/cron-env) "$@"

So then, as the user in question, I was able to

run-as-cron /the/problematic/script --with arguments --and parameters

This solution could obviously be expanded to make use of sudo or such for more flexibility.

Hope this helps others.

Best Answer

Related Solutions

Linux Cron – Can a Cron Job Run More Frequently Than Every Minute?

Cron Job – How to Run a Cron Job Manually and Immediately

Related Topic