Simple udev rule and script to allow switching between Yubikey smartcards for GPG use, without needing to clean directories each time
install clean-card-private-keys script in /usr/local/bin
sudo cp clean-card-private-keys /usr/local/bin/clean-card-private-keys
sudo chmod 755 /usr/local/bin/clean-card-private-keys
edit 40-yubikey.rules and replace CHANGEME with your Linux login name
sudo cp 40-yubikey.rules /etc/udev/rules.d/40-yubikey.rules
Not designed for linux systems with multiple users.