Hi folks, Does anyone know how to instruct cron to carry out a command when a connection to the internet is first made after boot? I have a few jobs that only need to be done once per day and require an internet connection e.g downloading the weather forecast and my rss feeds. I’m not always connected to the internet on boot and do not have the computer switched on at the same times every day. Many thanks for any suggestions.
Everyone else is just telling you to do things in a way that is different, and while they are correct (you should use a unit.d/systems script for this depending on your distro), I’m going to actually answer your question since I know sometimes you just need a quick and simple way.
Depending on your version of cron, it may support special statements instead of the * * * * * notation for time.
The one you want is @reboot. Replace all entries of the schedule syntax with that, including the @, and the command will be executed only once when the system boots up.
Use that to start a script that checks for network connectivity on a loop with a sleep statement. Break the loop when you have connectivity, then execute your command, and exit the script.
Don’t ignore the correct way though. You’re better off executing this as a systemd (or equivalent) script. It’s barely more effort, and has the benefit of some nice built in logging and integrations.