Cronjobs: When First Connected to Internet
Cronjobs: When First Connected to Internet
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.
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Personally I'd write a script to do whatever it is you want to do, checking first whether the internet connection is working. Said script can check the internet is working, if not, sleep for 10 minute or something, and try again, perhaps giving up after a set number of tries. Said script could also check the date and time of the file downloaded and confirm it is out of date.
Then, have the script execute on bootup by adding it to the startup scripts.
Instead of having it sleep 10 minutes just make it a cronjob that runs every 10 minutes and has a lockfile, much more robust that way.
If it should be done say only twice a day, then your way would be completely cumbersome.
If it should be done only twice a day sleeping for 12h would be even more error prone and you would be even less likely to have it actually run at that time.
Also, if it should be done only twice a day you don't really want it to run twice a day only since you can not guarrantee that you have internet exactly at the time when your timer expires, you would want to check some "last_updated" timestamp and check if it was more than 12h ago.