# Bash on Linux, 21 bytes

    xev|awk 'NR%2&&/\(k/'

Unfortunately, I can't test it since I'm on MacBook on Linux - no PrntScr, no numeric keyboard &all.

`xev` is a tool that outputs mouse and keyboard events under `X.org`. I pipe it to awk, filter even lines (since every key is shown when key is pressed, and then when it's released), and select only those that contain `(k` - this string is in every line that describes pressed key.