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

Return the IPv6 Zone ID

== Synopsis

Declared in `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/url_view_base.hpp#L1463[boost/url/url_view_base.hpp]>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<xref:boost/urls/string_token/StringToken.adoc[string_token::StringToken] StringToken = xref:boost/urls/string_token/return_string.adoc[string_token::return_string]>
StringToken::result_type
zone_id(StringToken&& token = {});
----

== Description

If the host type is xref:boost/urls/host_type.adoc[`host_type::ipv6`], this function returns the Zone ID as a string. Otherwise an empty string is returned. Any percent‐escapes in the string are decoded first.

== Example
[,cpp]
----
assert( url_view( "http://[fe80::1%25eth0]/" ).zone_id() == "eth0" );
----
== Complexity
Linear in `this‐>encoded_zone_id().size()`.

== Exception Safety
Calls to allocate may throw.

== BNF
[,cpp]
----
host        = IP-literal / IPv4address / reg-name

IP-literal = "[" ( IPv6address / IPv6addrz / IPvFuture  ) "]"

ZoneID = 1*( unreserved / pct-encoded )

IPv6addrz = IPv6address "%25" ZoneID
----
== Specification
* https://datatracker.ietf.org/doc/html/rfc6874[]

== Return Value

The Zone ID as a string.

== Parameters

[cols=2]
|===
| Name
| Description
| *token*
| A string token customization.
|===


[.small]#Created with https://www.mrdocs.com[MrDocs]#