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63<h1><a class="anchor" name="itfile">Writing and reading data from files </a></h1>Here we will use the <code>it_file</code> class to store some data. The program <code>write_it_file.cpp</code> looks as follows:<p>
64<div class="fragment"><pre class="fragment"><span class="preprocessor">#include &lt;itpp/itcomm.h&gt;</span>
65
66<span class="keyword">using namespace </span>itpp;
67
68<span class="keywordtype">int</span> main()
69{
70  <span class="comment">// Declare the it_file class</span>
71  it_file ff;
72
73  <span class="comment">// Open a file with the name "it_file_test.it"</span>
74  ff.open(<span class="stringliteral">"it_file_test.it"</span>);
75
76  <span class="comment">// Create some data to put into the file</span>
77  vec a = linspace(1, 20, 20);
78
79  <span class="comment">// Put the variable a into the file. The Name("a") tells the file class</span>
80  <span class="comment">// that the next variable shall be named "a".</span>
81  ff &lt;&lt; Name(<span class="stringliteral">"a"</span>) &lt;&lt; a;
82
83  <span class="comment">// Force the file to be written to disc. This is useful when performing</span>
84  <span class="comment">// iterations and ensures that the information is not stored in any cache</span>
85  <span class="comment">// memory. In this simple example it is not necessary to flush the file.</span>
86  ff.flush();
87
88  <span class="comment">// Close the file</span>
89  ff.close();
90
91  <span class="comment">// Exit program</span>
92  <span class="keywordflow">return</span> 0;
93}
94</pre></div><p>
95When you run this program you will obtain a file called <code>it_file_test.it</code> in your current directory. You can read the file into Matlab/Octave to view the data by using the following commands:<p>
96<div class="fragment"><pre class="fragment">itload(<span class="stringliteral">'it_file_test.it'</span>)
97figure(1); clf;
98plot(a)
99</pre></div><p>
100Note: Make sure that <code>$PREFIX/share/itpp</code> is in your Matlab/Octave path and that you run the code above from the directory where <code>it_file_test.it</code> is located (<code>$PREFIX</code> is the IT++ installation prefix; <code>/usr/local</code> by default).<p>
101The IT++ program <code>read_it_file.cpp</code> that reads the file and prints its content can look like this:<p>
102<div class="fragment"><pre class="fragment"></pre></div><p>
103Here is the output of the program:<p>
104<div class="fragment"><pre class="fragment">
105a = [1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20]
106</pre></div> </div>
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