This is a neat way to quickly generate a QR-code, for example to transfer text from computer to phone (thanks to Solène Rapenne for the original idea and implementation). On the phone, you'll of course need to use a QR-reader app, such as Binary Eye.

xclip -o -selection clipboard | qrencode -o - -t PNG | feh -g 600x600 -Z -

Using this command, whatever is in your clipboard will be encoded to QR and displayed on your monitor. Note that xclip can pull stuff from different clipboards, and in my case the contents were not picked up with -selection default but -selection clipboard did the trick.

Linux (well, really the window managers, so X11 and then, i3, Wayland, etc…​) have multiple clipboards. The default ones are the Primary selection one, and the Secondary one. The names are historical accidents, but the “primary” one always has a copy of the last text you selected from anywhere, which can be pasted anywhere by clicking the middle mouse button. You just select some text and that’s it - you don’t have to do anything else and you can then middle-click paste this anywhere. The “secondary” clipboard is the “normal” Cut, Copy, Paste, Ctrl+c, Ctrl+v one.
https://duncanlock.net/blog/2022/04/06/using-windows-after-15-years-on-linux/

I recently got a copy of my "digital covid certificate". (You can get yours at covidbevis.se).
The certificate contains a rather dense-looking QR code, so naturally I was curious as to what data it contained.

With the help of Binary Eye, I could see that whatever the QR code encoded was not stored in clear-text.

Searching the web, I encountered this blog post by Austrian hacker Tobias Girstmair.
He has written a Python script that deconstructs the QR code into its data fields.

I installed it and used it to read out the values from a JPG screenshot of my QR code (I have randomised or hidden some data to protect privacy):

$ git clone https://git.gir.st/greenpass.git/
$ cd greenpass
$ python3.8 -m venv venv,
$ source venv/bin/activate
$ pip3 install flynn base45 PyPDF2 pyzbar Pillow
$ sudo apt install libzbar0 
$ python3 greenpass.py myqrcode-screenshot.jpg
QR Code Issuer : SE
QR Code Expiry : 2021-09-29 15:00:00
QR Code Generated : 2021-07-01 15:00:00
 Vaccination Group
   Unique Certificate Identifier: UVCI : URN:UVCI:01:SE:EHM/V10050020P8X
   Country of Vaccination : SE
   Dose Number : 1
   ISO8601 complete date: Date of Vaccination : 2021-06-01
   Certificate Issuer : Swedish eHealth Agency
   Marketing Authorization Holder : ORG-100030215
   vaccine medicinal product : EU/1/20/1528
   Total Series of Doses : 2
   disease or agent targeted : 840539006
   vaccine or prophylaxis : J07BX03
 Date of birth : 1982-02-01
 Surname(s), forename(s)
   Surname : <>
   Forename : <>
   Standardised surname : <>
   Standardised forename : <>
 Schema version : 1.3.0

The script worked when supplying a screenshot, but threw an error when I tried supplying the HC1 hash itself. In any case, I congratulate Tobias on a very nice piece of investigative work, allowing citizens all over the EU to inspect the data they share when using their COVID vaccination certificate.