+.It Cm s
+Print a
+.Cm style
+attribute.
+If present, it must be the last format letter.
+It requires two
+.Va char *
+arguments.
+The first is the name of the style property, the second its value.
+The name must not be
+.Dv NULL .
+The
+.Cm s
+.Ar fmt
+letter can be repeated, each repetition requiring an additional pair of
+.Va char *
+arguments.