Why opaque URI shall not begin with single slash ('/'), not double-slash ('//')? Any practical example of URI with just one slash?

Question

A URI is opaque if, and only if, it is absolute and its scheme-specific part does not begin with a slash character ('/'). An opaque URI has a scheme, a scheme-specific part, and possibly a fragment; all other components are undefined.

But all URI/URL having a protocol (scheme) I always see two slashes (like http:// ).

Is there a practically used example of an URI or URL with a single / after protocol?

Answer 1

并非每个分层URI方案都需要一个权限组件。最值得注意的是，file:方案不需要一个。 file:/home/vgr是有效的URI。