19.2.2.4.2 Restrictions on Examining a Pathname Device Component

The device might be a string, :wild, :unspecific, or nil.

Note that :wild might result from an attempt to read[1] the pathname component, even though portable programs are restricted from writing[1] such a component value; see Section 19.2.2.3 (Restrictions on Wildcard Pathnames) and Section 19.2.2.5 (Restrictions on Constructing Pathnames).