.sp
.IR "key " ,[ "key " ,...]
.P
+Each key has the following format:
+.sp
+.IR "name op value"
+.P
+There are distinct key operation types, depending on the type of the key, it
+does a comparison or an assignment.
+.P
+Comparison operators are:
+.TP
+.B ==
+Compare for equality.
+.TP
+.B !=
+Compare for non-equality.
+.P
+Assignment operators are:
+.TP
+.B +=
+Add the value to a key that holds a list of entries.
+.TP
+.B :=
+Assign a value to a key finally; disallow any later changes, which
+is useful to prevent changes by any later rules.
+.TP
+.B =
+Asign a value to a key. Keys that represent a list, are reset and only this
+single value is assigned. While this operator still works inplicitely as
+comparison on keys that can't get a value assigned, its usage as an comparison
+operator is deprecated.
+.P
The following key names can be used to match against device properties:
.TP
.B BUS
.SH "SEE ALSO"
.BR udevinfo (8),
.BR udevd (8),
-.BR hotplug (8)
.PP
.B Web resources:
.nf