$ udevadm monitor
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing
KERNEL - the kernel uevent

KERNEL[7163.757337] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6 (usb)
KERNEL[7163.758397] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6/1-6:1.0 (usb)
KERNEL[7163.758500] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6/1-6:1.1 (usb)
UDEV  [7163.764236] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6 (usb)
KERNEL[7163.767166] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6/1-6:1.1/tty/ttyACM0 (tty)
KERNEL[7163.767246] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6/1-6:1.2 (usb)
KERNEL[7163.767356] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6/1-6:1.3 (usb)
KERNEL[7163.767571] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6/1-6:1.4 (usb)
UDEV  [7163.769130] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6/1-6:1.1 (usb)
UDEV  [7163.771770] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6/1-6:1.0 (usb)
UDEV  [7163.773214] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6/1-6:1.2 (usb)
UDEV  [7163.774705] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6/1-6:1.1/tty/ttyACM0 (tty)
UDEV  [7163.779169] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6/1-6:1.4 (usb)
UDEV  [7163.779749] add      /devices/pci0000:00/0000:00:1a.7/usb1/1-6/1-6:1.3 (usb)