:relfileprefix: ../../../
[#boost-urls-url_view_base-scheme]

= xref:boost.adoc[pass:[boost]]::xref:boost/urls.adoc[pass:[urls]]::xref:boost/urls/url_view_base.adoc[pass:[url_view_base]]::scheme


Return the scheme


== Synopsis

Declared in header `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/url_view_base.hpp#L375[boost/url/url_view_base.hpp,window=blank_]>`

[source,cpp,subs="verbatim,macros,-callouts"]
----
core::string_view
scheme() const noexcept;
----

== Description


This function returns the scheme if it
exists, without a trailing colon (':').
Otherwise it returns an empty string.
Note that schemes are case-insensitive,
and the canonical form is lowercased.

=== Example
[,cpp]
----
assert( url_view( "http://www.example.com" ).scheme() == "http" );
----

=== Exception Safety

Throws nothing.

=== BNF
[,cpp]
----
scheme          = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )

URI             = scheme ":" hier-part [ "?" query ] [ "#" fragment ]

absolute-URI    = scheme ":" hier-part [ "?" query ]
----

=== Specification

* link:https://datatracker.ietf.org/doc/html/rfc3986#section-3.1[3.1. Scheme (rfc3986)]








== See Also


xref:boost/urls/url_view_base/has_scheme.adoc[has_scheme]
,
xref:boost/urls/url_view_base/scheme_id.adoc[scheme_id]
.