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<title>Simple wget — cpp-netlib v0.10.0</title>
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<div class="section" id="simple-wget">
<span id="id1"></span><h1>Simple <cite>wget</cite><a class="headerlink" href="#simple-wget" title="Permalink to this headline">¶</a></h1>
<p>This example is a very simple implementation of a <tt class="docutils literal"><span class="pre">wget</span></tt> style
clone. It’s very similar to the previous example, but introduces the
<tt class="docutils literal"><span class="pre">uri</span></tt> class.</p>
<div class="section" id="the-code">
<h2>The code<a class="headerlink" href="#the-code" title="Permalink to this headline">¶</a></h2>
<div class="highlight-c++"><div class="highlight"><pre><span class="cp">#include <boost/network/protocol/http/client.hpp></span>
<span class="cp">#include <boost/network/uri.hpp></span>
<span class="cp">#include <string></span>
<span class="cp">#include <fstream></span>
<span class="cp">#include <iostream></span>
<span class="k">namespace</span> <span class="n">http</span> <span class="o">=</span> <span class="n">boost</span><span class="o">::</span><span class="n">network</span><span class="o">::</span><span class="n">http</span><span class="p">;</span>
<span class="k">namespace</span> <span class="n">uri</span> <span class="o">=</span> <span class="n">boost</span><span class="o">::</span><span class="n">network</span><span class="o">::</span><span class="n">uri</span><span class="p">;</span>
<span class="k">namespace</span> <span class="p">{</span>
<span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">get_filename</span><span class="p">(</span><span class="k">const</span> <span class="n">uri</span><span class="o">::</span><span class="n">uri</span> <span class="o">&</span><span class="n">url</span><span class="p">)</span> <span class="p">{</span>
<span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">path</span> <span class="o">=</span> <span class="n">uri</span><span class="o">::</span><span class="n">path</span><span class="p">(</span><span class="n">url</span><span class="p">);</span>
<span class="n">std</span><span class="o">::</span><span class="kt">size_t</span> <span class="n">index</span> <span class="o">=</span> <span class="n">path</span><span class="p">.</span><span class="n">find_last_of</span><span class="p">(</span><span class="sc">'/'</span><span class="p">);</span>
<span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">filename</span> <span class="o">=</span> <span class="n">path</span><span class="p">.</span><span class="n">substr</span><span class="p">(</span><span class="n">index</span> <span class="o">+</span> <span class="mi">1</span><span class="p">);</span>
<span class="k">return</span> <span class="n">filename</span><span class="p">.</span><span class="n">empty</span><span class="p">()</span><span class="o">?</span> <span class="s">"index.html"</span> <span class="o">:</span> <span class="n">filename</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">}</span> <span class="c1">// namespace</span>
<span class="kt">int</span>
<span class="n">main</span><span class="p">(</span><span class="kt">int</span> <span class="n">argc</span><span class="p">,</span> <span class="kt">char</span> <span class="o">*</span><span class="n">argv</span><span class="p">[])</span> <span class="p">{</span>
<span class="k">if</span> <span class="p">(</span><span class="n">argc</span> <span class="o">!=</span> <span class="mi">2</span><span class="p">)</span> <span class="p">{</span>
<span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o"><<</span> <span class="s">"Usage: "</span> <span class="o"><<</span> <span class="n">argv</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o"><<</span> <span class="s">" url"</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
<span class="k">return</span> <span class="mi">1</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">try</span> <span class="p">{</span>
<span class="n">http</span><span class="o">::</span><span class="n">client</span> <span class="n">client</span><span class="p">;</span>
<span class="n">http</span><span class="o">::</span><span class="n">client</span><span class="o">::</span><span class="n">request</span> <span class="n">request</span><span class="p">(</span><span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">]);</span>
<span class="n">http</span><span class="o">::</span><span class="n">client</span><span class="o">::</span><span class="n">response</span> <span class="n">response</span> <span class="o">=</span> <span class="n">client</span><span class="p">.</span><span class="n">get</span><span class="p">(</span><span class="n">request</span><span class="p">);</span>
<span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">filename</span> <span class="o">=</span> <span class="n">get_filename</span><span class="p">(</span><span class="n">request</span><span class="p">.</span><span class="n">uri</span><span class="p">());</span>
<span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="s">"Saving to: "</span> <span class="o"><<</span> <span class="n">filename</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
<span class="n">std</span><span class="o">::</span><span class="n">ofstream</span> <span class="n">ofs</span><span class="p">(</span><span class="n">filename</span><span class="p">.</span><span class="n">c_str</span><span class="p">());</span>
<span class="n">ofs</span> <span class="o"><<</span> <span class="k">static_cast</span><span class="o"><</span><span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">></span><span class="p">(</span><span class="n">body</span><span class="p">(</span><span class="n">response</span><span class="p">))</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">catch</span> <span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">exception</span> <span class="o">&</span><span class="n">e</span><span class="p">)</span> <span class="p">{</span>
<span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o"><<</span> <span class="n">e</span><span class="p">.</span><span class="n">what</span><span class="p">()</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
<span class="k">return</span> <span class="mi">1</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="section" id="running-the-example">
<h2>Running the example<a class="headerlink" href="#running-the-example" title="Permalink to this headline">¶</a></h2>
<p>You can then run this to copy the <a class="reference external" href="http://www.boost.org/">Boost</a> website:</p>
<div class="highlight-bash"><div class="highlight"><pre><span class="nv">$ </span><span class="nb">cd</span> ~/cpp-netlib-build
<span class="nv">$ </span>make simple_wget
<span class="nv">$ </span>./example/simple_wget http://www.boost.org/
<span class="nv">$ </span>cat index.html
</pre></div>
</div>
</div>
<div class="section" id="diving-into-the-code">
<h2>Diving into the code<a class="headerlink" href="#diving-into-the-code" title="Permalink to this headline">¶</a></h2>
<p>As with <tt class="docutils literal"><span class="pre">wget</span></tt>, this example simply makes an HTTP request to the
specified resource, and saves it on the filesystem. If the file name
is not specified, it names the resultant file as <tt class="docutils literal"><span class="pre">index.html</span></tt>.</p>
<p>The new thing to note here is use of the <tt class="docutils literal"><span class="pre">uri</span></tt> class. The <tt class="docutils literal"><span class="pre">uri</span></tt>
takes a string as a constructor argument and parses it. The <tt class="docutils literal"><span class="pre">uri</span></tt>
parser is fully-compliant with <a class="reference external" href="http://www.ietf.org/rfc/rfc3986.txt">RFC 3986</a>. The URI is provided in
the following header:</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="cp">#include <boost/network/uri.hpp></span>
</pre></div>
</div>
<p>Most of the rest of the code is familiar from the previous example.
To retrieve the URI resource’s file name, the following function is
provided:</p>
<div class="highlight-c++"><div class="highlight"><pre><span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">get_filename</span><span class="p">(</span><span class="k">const</span> <span class="n">uri</span><span class="o">::</span><span class="n">uri</span> <span class="o">&</span><span class="n">url</span><span class="p">)</span> <span class="p">{</span>
<span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">path</span> <span class="o">=</span> <span class="n">uri</span><span class="o">::</span><span class="n">path</span><span class="p">(</span><span class="n">url</span><span class="p">);</span>
<span class="n">std</span><span class="o">::</span><span class="kt">size_t</span> <span class="n">index</span> <span class="o">=</span> <span class="n">path</span><span class="p">.</span><span class="n">find_last_of</span><span class="p">(</span><span class="sc">'/'</span><span class="p">);</span>
<span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">filename</span> <span class="o">=</span> <span class="n">path</span><span class="p">.</span><span class="n">substr</span><span class="p">(</span><span class="n">index</span> <span class="o">+</span> <span class="mi">1</span><span class="p">);</span>
<span class="k">return</span> <span class="n">filename</span><span class="p">.</span><span class="n">empty</span><span class="p">()</span><span class="o">?</span> <span class="s">"index.html"</span> <span class="o">:</span> <span class="n">filename</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
<p>The <tt class="docutils literal"><span class="pre">uri</span></tt> interface provides access to its different components:
<tt class="docutils literal"><span class="pre">scheme</span></tt>, <tt class="docutils literal"><span class="pre">user_info</span></tt>, <tt class="docutils literal"><span class="pre">host</span></tt>, <tt class="docutils literal"><span class="pre">port</span></tt>, <tt class="docutils literal"><span class="pre">path</span></tt>, <tt class="docutils literal"><span class="pre">query</span></tt> and
<tt class="docutils literal"><span class="pre">fragment</span></tt>. The code above takes the URI path to determine the
resource name.</p>
<p>Next we’ll develop a simple client/server application using
<tt class="docutils literal"><span class="pre">http::server</span></tt> and <tt class="docutils literal"><span class="pre">http::client</span></tt>.</p>
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<ul>
<li><a class="reference internal" href="#">Simple <cite>wget</cite></a><ul>
<li><a class="reference internal" href="#the-code">The code</a></li>
<li><a class="reference internal" href="#running-the-example">Running the example</a></li>
<li><a class="reference internal" href="#diving-into-the-code">Diving into the code</a></li>
</ul>
</li>
</ul>
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