$$
The $ character.
12.6.3
Using udev Match Keys
Match keys describe conditions that must be met before a udev rule can be applied.
The following match keys are available:
ACTION
The name of the event action, for example, add or remove when adding or remov-
ing a device.
DEVPATH
The device path of the event device, for example,
DEVPATH=/bus/pci/drivers/ipw3945 to search for all events related to
the ipw3945 driver.
KERNEL
The internal (kernel) name of the event device.
SUBSYSTEM
The subsystem of the event device, for example, SUBSYSTEM=usb for all events
related to USB devices.
ATTR{filename}
sysfs attributes of the event device. To match a string contained in the vendor
attribute le name, you could use ATTR{vendor}=="On[sS]tream", for
example.
KERNELS
Let udev search the device path upwards for a matching device name.
SUBSYSTEMS
Let udev search the device path upwards for a matching device subsystem name.
DRIVERS
Let udev search the device path upwards for a matching device driver name.
Dynamic Kernel Device Management with udev 215
