At $DAYJOB, email is handled through Microsoft’s Office 365, and with that I occasionally get event invitations in Microsofts’s internal format. As I am using an IMAP-based e-mail client (since I cannot stand Outlook Web Access), actually reading those invites can be a bit difficult.

With the default settings, the invitations are presented as a link into the Outlook Web Access client, with only the subject of the event readable (as the email subject). Everything else is completely hidden from the user. Thunderbird does have some built-in code that downloads the calendaring information and displays it to the user, but I am using a different email client and only get the web link.

Entering Outlook Web Access and going into the settings, there is a setting to present invites as Icalendar files (MIME type text/calendar, extension .ics). Enabling this changes the emails so that the event text is presented in the message body, but all the important details, such as start time and location, are only present in the Icalendar file. And while the calendar is “readable” in the sense that it is a text file, it is not readable in the sense that it is easy to find out what it says.

I am running Linux on my desktop, and do not have any calendaring software installed, so nothing wants to pick up the .ics file. And reading it in a text editor isn’t easy. There are several timestamps, and it takes a while to figure out that it is the third DTSTART entry that contains the event start time:

$ grep DT attachment.ics
DTSTART:16010101T030000
DTSTART:16010101T020000
DTSTART;TZID=W. Europe Standard Time:20211103T100000
DTEND;TZID=W. Europe Standard Time:20211103T142500
DTSTAMP:20211102T150149Z

Trying to find software that will just view an ics file in a readable format isn’t easy. I don’t need calendaring software on my desktop (I do have a calendar app on my phone that I could use, though), but it would be nice to display it.

After some intense web searching, I found mutt-ics, a plug-in for the textual Mutt e-mail client. I am not using Mutt, but running the script on the ics file did produce readable output:

$ python ./mutt_ics/mutt_ics.py /tmp/attachment857.ics
[...]
Start: Wednesday, 03 November 2021, 10:00 CET
End: Wednesday, 03 November 2021, 14:25 CET

That’s a step forward. The next issue is that I am using a graphical e-mail client, and this is a text-mode script. The e-mail software runs “xdg-open” to open the file, so I had to create a few items to get it working. First, a script wrapper that runs the script and shows the output using “xmessage” (other software also works, I have not yet found out how to get xmessage to display UTF-8 text properly, so I might need to replace it eventually):

#!/bin/bash
python /home/peter/mutt-ics/mutt_ics/mutt_ics.py "$1" | iconv -c -f UTF-8 -t ISO8859-1 | xmessage -file -
exit 0

Next step was to make a .desktop file that defines the script as a handler for the text/calendar MIME type:

$ cat /home/peter/.local/share/applications/view-ics.desktop
[Desktop Entry]
Type=Application
Version=1.0
Name=View iCalendar
Exec=/home/peter/bin/view_ics
Terminal=false
MimeType=text/calendar;
StartypNotify=false

And to tie it all together, I have to register it as the default handler for text/calendar by running xdg-mime:

xdg-mime default view-ics.desktop text/calendar

There, now running “xdg-open file.ics” opens a xmessage dialog showing the calendar details in a new window. Managed to get it working just in time, the meeting starts in twenty minutes…