add_users() {
	_l="/etc/login.defs"
	_p="/etc/passwd"

	## get mini UID limit ##
	l=$(grep "^UID_MIN" $_l)

	## get max UID limit ##
	l1=$(grep "^UID_MAX" $_l)

	## use awk to print if UID >= $MIN and UID <= $MAX and shell is not /sbin/nologin ##
	users=$(awk -F':' -v "min=${l##UID_MIN}" -v "max=${l1##UID_MAX}" '{ if ( $3 >= min && $3 <= max  && $7 != "/sbin/nologin" ) print $0 }' "$_p" | cut -d: -f1)
	for i in $users; do
		echo "Adding user '$i' to user-group 'input,video'"
		usermod -a -G input "$i"
		usermod -a -G video "$i"
	done
}

add_group() {
	getent group "input" &>/dev/null || groupadd -r input -g 97
	getent group "video" &>/dev/null || groupadd -r video -g 91
	add_users
}

post_install() {
	post_upgrade
}

post_upgrade() {
	systemctl --global enable libinput-gestures
	add_group
}
