sudofry 
UPDATE – This No Longer Works!
These steps explain how to get the full user Id of every Magic the Gathering Arena player that you have battled since the time you opened the game this session. The user Ids are stored in a log file (if logging is turned on) and there are quite a few search results explaining how to find this log file in Windows and MAC, but I couldn’t really find anything that explained where this file was located in Linux for players that run MTGA with Lutris. I found the file and threw together a command that grabs each unique user Id (excluding your own) and displays them for you so you can add new friends when you have an epic battle and you want some more.
First open MTGA and click on the Settings gear. Next click on “Account” at the bottom. Then check the box that says “Detailed Logs (Plugin Support)”.
Close MTGA.
Now it will start saving a detailed log file. Every person you battle will show up in this file until you close and re-open a new game session.
Path to the logfile where you can find a user’s full user Id.
/home/your-pc-username/Games/magic-the-gathering-arena/drive_c/Program Files/Wizards of the Coast/MTGA/MTGA_Data/Logs/Logs
I wrote the following command to strip out each user Id (excluding your own) from the rest of the file. Each player you battled this session will show up. This file will delete itself and recreate a new file each time you close MTGA and re-open it.
Change the sections in green to your info.
your-pc-username – Example: sudofry
your-MTGA-userId – Example: sudofry#12345
grep -oP "playerName.{0,25}" "/home/your-pc-username/Games/magic-the-gathering-arena/drive_c/Program Files/Wizards of the Coast/MTGA/MTGA_Data/Logs/Logs/"*.log | cut -c 15- | sed 's/".*//' | awk '!seen[$0]++' | awk '{ if (/your-MTGA-userId/ && !seen) {seen = 1} else print }'
If you add the following line to the end of the command (make sure to add the space at the beginning) and save it in a script, whenever you run the script it will create a text file on your desktop with all of the user Id’s.
> /home/your-pc-username/Desktop/ArenaUsers.txt
Now set this script to launch with a keyboard combo and you can overwrite this file with an updated list any time you press the combo.
