Use crontab to notify when a piece of software has been released

Sometimes I eagerly await the release of a distro version or a new version of a piece of software. But I don't want to remember to check constantly, so I wrote a script that can be run from cron to let me know.

#!/bin/sh
case $# in
0|1)
       echo Usage: $0 url message
       exit
       ;;
esac
url="$1"
shift
wget -q --spider "$url" && echo "$@"

As you can see, this runs a wget on a specified URL which does not produce any output, but if successful, will print the message. Put this in crontab and the message will be mailed to you.

This script depends on knowing a URL that will exist when the release happens. Often you can guess the URL from previous releases. Here are a couple of examples, each is all on a single line:

1. Check at 0808 every day to see if AntiX 17 has been released:

8 8 * * * watchurl https://sourceforge.net/projects/antix-linux/files/Final/antiX-17/ AntiX 17 released

2. Check at 0809 every day to see if VirtualBox 5.1.30 has been released:

9 8 * * * watchurl https://www.virtualbox.org/download/hashes/5.1.30/MD5SUMS VirtualBox 5.1.30 has been released

Rebuild kernel modules for VirtualBox on Linux automatically

I prefer to install packages distributed by VirtualBox rather than packages built by the distro maintainers as I don't have to wait for a new package when a new kernel is released. Unfortunately this involves rebuilding the vbox kernel modules after the new kernel is booted. So I decided to devise a way to automate this.

First I wrote a script to check if the vbox modules are loaded and if not to run the setup script. It's just this:

#!/bin/sh

sleep 120
if ! lsmod | grep -s vbox > /dev/null
then
       /usr/lib/virtualbox/vboxdrv.sh setup
fi

The sleep is needed as in some init systems cron comes up even before all the modules are loaded. Next, I installed a crontab entry that runs the script above once at bootup, using the @reboot notation:

@reboot /root/bin/vboxdrv

This goes into root's crontab, using crontab -e.

And voilà, that's all that's needed.