I am not a big fan of Facebook’s Pavlovification of life, and I try and spend as little time as possible on it. This, unfortunately, has lead to me missing invites to things.

I was shooting the shit with a mate of mine recently, who is even more anti-Facebook, and here’s what I came up with.

iCal Feeds

One of the hidden features Facebook has is that it’s feed of events you’re going to or have been invited to, is made available via an iCal feed you can subscribe to. I had already added this to my Google calendar (add another calendar by URL), so I get a list of upcoming events appearing in my calendar, and you can even tell Google calendar to send you a notification email when new stuff is added.

However, Google has its own problems, so I thought it’d be nice to get a weekly email digest of upcoming things.

Python lists

So, using the python-icalendar module, I wrote a very quick bit of python program that you an point at an ical feed, and get a summary list of upcoming events printed to the console in a nice list. It uses the summary text of the event, together with the start and end times, and, if available, the location and URL link (handy for Facebook events).

It automatically removes events that have already ended, and by default only lists events that start within the next 7 days.

Use it as follows:

python parse_cal.py -u 'https://url.of.feed/ical' -d *numberofdays*

Which outputs something like:

     2016-02-24 19:30 - 2016-02-24 22:30
     Wheatsheaf Oxford
     2016-02-25 20:00 - 2016-02-26 01:00
     The Bullingdon  (Oxford)

Which are two awesome events I’m heading to in the next few weeks (two very different styles of music!)

Now the email

Getting a weekly digest then is just a matter of a bit of cron and mailer goodness, edit your crontab thus:

@weekly /usr/bin/python /path/to/parse_cal.py -u 'https://feed.example.com/calendar.ics' -d 7 | mail -E -s "This week's upcoming events" you@example.com

The program only outputs something if it finds things, so the -E tells mailx to not send anything if there’s no message body.

And you’re done!

I’ve found this pretty handy for a few other calendar feeds (my work joblist for example). Enjoy!

» Visit the project on Github...

iCal is a simple format for sharing calendar, event and todo list information between applications. It is widely supported by many many applications.

I have recently been hacking on a couple of projects which required me to implement the format, and during this I hit on a couple of less well documented gotchas.

So, I’ve jotted them down here in order to hopefully save you some time…

  • Line endings: The specification says that line endings should be CRLF only, and some less tolerant clients puke if they’re not.
  • No blank lines: Ensure that your output contains no blank lines, again some clients with puke or interpret these as the end of the file.
  • End in .ics (the biggy): This is important if you dynamically generate an iCal feed for use with Google Calendar. You should set header type appropriately, e.g.

    header("Content-Type: text/calendar");
    header('Content-Disposition: attachment; filename="calendar.ics"');

    But critically, if all your entries are showing up only as “Busy”, you must also end the URL you pass to Google calendar as http://foo.com/bar/whatever.ics

You may find one of these validator tools useful too.

Hope that helps!

Image “Calendar Logo” by Quadmod