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<h1 class="lined-header"><span>cowboy_req:header(3)</span></h1>

<h2 id="_name">Name</h2>
<p>cowboy_req:header - HTTP header</p>
<h2 id="_description">Description</h2>
<div class="listingblock"><div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><b><font color="#000000">header</font></b>(<font color="#009900">Name</font>, <font color="#009900">Req</font>)          <font color="#990000">-&gt;</font> <b><font color="#000000">header</font></b>(<font color="#009900">Name</font>, <font color="#009900">Req</font>, <font color="#000080">undefined</font>)
<b><font color="#000000">header</font></b>(<font color="#009900">Name</font>, <font color="#009900">Req</font>, <font color="#009900">Default</font>) <font color="#990000">-&gt;</font> <b><font color="#000080">binary</font></b>() | <font color="#009900">Default</font>

<font color="#009900">Name</font>    <font color="#990000">::</font> <b><font color="#000080">binary</font></b>()          <i><font color="#9A1900">%% lowercase; case insensitive</font></i>
<font color="#009900">Req</font>     <font color="#990000">::</font> <b><font color="#000000">cowboy_req:req</font></b>()
<font color="#009900">Default</font> <font color="#990000">::</font> <b><font color="#000000">any</font></b>()</tt></pre>
</div></div>
<p>Return the value for the given HTTP header.</p>
<p>The header name must be given as a lowercase binary string. While header names are case insensitive, Cowboy requires them to be given as lowercase to function properly.</p>
<p>Headers can also be obtained using pattern matching:</p>
<div class="listingblock"><div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>#{<font color="#FF6600">headers</font> <font color="#990000">:=</font> #{<font color="#009900">Name</font> <font color="#990000">:=</font> <font color="#009900">Value</font>}} <font color="#990000">=</font> <font color="#009900">Req</font><font color="#990000">.</font></tt></pre>
</div></div>
<p>Note that this snippet will crash if the header is missing.</p>
<h2 id="_arguments">Arguments</h2>
<dl><dt>Name</dt>
<dd><p>Desired HTTP header name as a lowercase binary string.</p>
</dd>
<dt>Req</dt>
<dd><p>The Req object.</p>
</dd>
<dt>Default</dt>
<dd><p>Default value returned when the header is missing.</p>
</dd>
</dl>
<h2 id="_return_value">Return value</h2>
<p>The header value is returned as a binary string. When the header is missing, the default argument is returned.</p>
<h2 id="_changelog">Changelog</h2>
<ul><li><strong>2.0</strong>: Only the header value is returned, it is no longer wrapped in a tuple.
</li>
<li><strong>1.0</strong>: Function introduced.
</li>
</ul>
<h2 id="_examples">Examples</h2>
<div class="listingblock"><div class="title">Get the accept header</div>
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><font color="#009900">Accept</font> <font color="#990000">=</font> <b><font color="#000000">cowboy_req:header</font></b>(<font color="#990000">&lt;&lt;</font><font color="#FF0000">"accept"</font><font color="#990000">&gt;&gt;</font>, <font color="#009900">Req</font>)<font color="#990000">.</font></tt></pre>
</div></div>
<div class="listingblock"><div class="title">Get the content-length header with a default value</div>
<div class="content"><!-- Generator: GNU source-highlight 3.1.8
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><font color="#009900">Length</font> <font color="#990000">=</font> <b><font color="#000000">cowboy_req:header</font></b>(<font color="#990000">&lt;&lt;</font><font color="#FF0000">"content-length"</font><font color="#990000">&gt;&gt;</font>, <font color="#009900">Req</font>, <font color="#990000">&lt;&lt;</font><font color="#FF0000">"0"</font><font color="#990000">&gt;&gt;</font>)<font color="#990000">.</font></tt></pre>
</div></div>
<h2 id="_see_also">See also</h2>
<p><a href="../cowboy_req">cowboy_req(3)</a>, <a href="../cowboy_req.headers">cowboy_req:headers(3)</a>, <a href="../cowboy_req.parse_header">cowboy_req:parse_header(3)</a></p>






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