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= cowboy_req:parse_qs(3)

== Name

cowboy_req:parse_qs - Parse the query string

== Description

[source,erlang]
----
parse_qs(Req :: cowboy_req:req())
    -> [{Key :: binary(), Value :: binary() | true}]
----

Parse the query string as a list of key/value pairs.

== Arguments

Req::

The Req object.

== Return value

The parsed query string is returned as a list of key/value pairs.
The key is a binary string. The value is either a binary string,
or the atom `true`. Both key and value are case sensitive.

The atom `true` is returned when a key is present in the query
string without a value. For example, in the following URIs
the key `<<"edit">>` will always have the value `true`:

* `/posts/42?edit`
* `/posts/42?edit&exclusive=1`
* `/posts/42?exclusive=1&edit`
* `/posts/42?exclusive=1&edit&from=web`

== Changelog

* *2.0*: The parsed value is not longer cached in the Req object.
* *2.0*: Only the parsed query string is returned, it is no longer wrapped in a tuple.
* *2.0*: Function introduced. Replaces `qs_val/1` and `qs_vals/1`.

== Examples

.Parse the query string and convert the keys to atoms
[source,erlang]
----
ParsedQs = cowboy_req:parse_qs(Req),
AtomsQs = [{binary_to_existing_atom(K, latin1), V}
    || {K, V} <- ParsedQs].
----

== See also

link:man:cowboy_req(3)[cowboy_req(3)],
link:man:cowboy_req:qs(3)[cowboy_req:qs(3)],
link:man:cowboy_req:match_qs(3)[cowboy_req:match_qs(3)]