error: `boost' has not been declared
<p>I'm trying to use boost libraries in my C++ application. I'm trying to compile it using g++ with different options.e.g <code>g++ -I /usr/include/boost/filesystem/ -o test.out test.cpp</code> however it always prompt  <code>error: 'boost' has not been declared</code>.  </p>

<p>And here is my code:</p>

<pre><code>#include &lt;fstream&gt;
#include &lt;iostream&gt;
#include &lt;string&gt;
#include &lt;vector&gt;
#include &lt;boost/filesystem.hpp&gt;
using namespace std;
int main (){
    string line;
    string fileName = "Read.txt";
    ifstream file;
    string str; 
    file.open(fileName.c_str());
    cout &lt;&lt; "Hello, world!\n";
    vector&lt;string&gt;  fileLines;

    fileLines.clear();
    while (getline(file, str))
    {
        fileLines.push_back(line);
    }
    cout &lt;&lt; "Total Line count:"&lt;&lt;fileLines.size()&lt;&lt;endl;
    fileLines.clear();
    cout &lt;&lt; "Total Line count:"&lt;&lt;fileLines.size()&lt;&lt;endl;
    boost::filesystem::path p("/tmp/foo.txt");


    return 0;
}
</code></pre>

<p>I will be glad if you help me to fix this.</p>

<p>P.S. I'm compiling my application in Centos 4.7 and It contains Boost version 1.32 according to <code>/usr/include/boost/version.hpp</code></p>

<p><strong>Update:</strong></p>

<p>I also commented boost instruction, but there is some problem with includes: <code>boost/filesystem.hpp: No such file or directory</code>.</p>