-.P
-The environment must provide the following variables:
-.TP
-.B ACTION
-.IR add " or " remove
-signifies the connection or disconnection of a device.
-.TP
-.B DEVPATH
-The sysfs devpath of the device without the mountpoint but a leading slash.
-.P
-Additional optional environment variables:
-.TP
-.B UDEV_CONFIG_FILE
-Overrides the default location of the
-.B udev
-config file.
-.TP
-.B UDEV_NO_SLEEP
-The default behavior of
-.B udev
-is to wait until all the sysfs files of the device chain are populated. If set,
-.B udev
-will continue, regardless of the state of the device representation.
-.TP
-.B UDEV_NO_DEVD
-The default behavior of
-.B udev
-is to execute programs in the
-.I /etc/dev.d/
-directory after device handling. If set,
-.B udev
-will skip this step.