:relfileprefix: ../../../
[#boost-urls-url-set_host]

= xref:boost.adoc[pass:[boost]]::xref:boost/urls.adoc[pass:[urls]]::xref:boost/urls/url.adoc[pass:[url]]::set_host


Set the host


== Synopsis

Declared in header `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/url.hpp#L438[boost/url/url.hpp,window=blank_]>`

[source,cpp,subs="verbatim,macros,-callouts"]
----
xref:boost/urls/url.adoc[url]&
set_host(core::string_view s);
----

== Description


Depending on the contents of the passed
string, this function sets the host:

* If the string is a valid IPv4 address,
then the host is set to the address.
The host type is
xref:boost/urls/host_type/ipv4.adoc[host_type::ipv4]
.

* If the string is a valid IPv6 address
enclosed in square brackets, then the
host is set to that address.
The host type is
xref:boost/urls/host_type/ipv6.adoc[host_type::ipv6]
.

* If the string is a valid IPvFuture
address enclosed in square brackets, then
the host is set to that address.
The host type is
xref:boost/urls/host_type/ipvfuture.adoc[host_type::ipvfuture]
.

* Otherwise, the host name is set to
the string, which may be empty.
Reserved characters in the string are
percent-escaped in the result.
The host type is
xref:boost/urls/host_type/name.adoc[host_type::name]
.

In all cases, when this function returns,
the URL contains an authority.

=== Example
[,cpp]
----
assert( url( "http://www.example.com" ).set_host( "127.0.0.1" ).buffer() == "http://127.0.0.1" );
----

=== Postconditions
[,cpp]
----
this->has_authority() == true
----

=== Complexity

Linear in `this-&gt;size() + s.size()`.

=== Exception Safety

Strong guarantee.
Calls to allocate may throw.

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

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

reg-name    = *( unreserved / pct-encoded / "-" / ".")
----

=== Specification

* link:https://en.wikipedia.org/wiki/IPv4[IPv4 (Wikipedia)]

* link:https://datatracker.ietf.org/doc/html/rfc4291[IP Version 6 Addressing Architecture (rfc4291)]

* link:https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2[            3.2.2. Host (rfc3986)]





== Parameters

|===
| Name | Description 

| *s*
| 
The string to set.

|===




== See Also


xref:boost/urls/url_base/set_encoded_host.adoc[set_encoded_host]
,
xref:boost/urls/url_base/set_encoded_host_address.adoc[set_encoded_host_address]
,
xref:boost/urls/url_base/set_encoded_host_name.adoc[set_encoded_host_name]
,
xref:boost/urls/url_base/set_host_address.adoc[set_host_address]
,
xref:boost/urls/url_base/set_host_ipv4.adoc[set_host_ipv4]
,
xref:boost/urls/url_base/set_host_ipv6.adoc[set_host_ipv6]
,
xref:boost/urls/url_base/set_host_ipvfuture.adoc[set_host_ipvfuture]
,
xref:boost/urls/url_base/set_host_name.adoc[set_host_name]
.



