[#boost-urls-string_to_scheme]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::string_to_scheme
:relfileprefix: ../../
:mrdocs:


Return the known scheme for a non‐normalized string, if known

== Synopsis


Declared in `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/scheme.hpp#L141[boost/url/scheme.hpp]>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:boost/urls/scheme.adoc[scheme]
string_to_scheme(core::string_view s) noexcept;
----

== Description


If the string does not identify a known    scheme, the value xref:boost/urls/scheme.adoc[scheme::unknown] is    returned.


=== BNF

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

=== Specification

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



== Return Value


The known scheme



== Parameters


|===
| Name | Description

| *s*
| The string holding the scheme


|===



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