prompt sudo once and forget about it

sudo_once.sh

startsudo()
{
	sudo -v
	( while true; do sudo -v; sleep 50; done; ) &
	SUDO_PID="$!"
	trap stopsudo SIGINT SIGTERM
}
stopsudo()
{
	kill "$SUDO_PID"
	trap - SIGINT SIGTERM
	sudo -k
}