title: The meaning of real, user, and sys in output of Linux time command
body: <pre><code>$ time ./Test 
  
  real    0m2.906s
  user    0m2.887s
  sys     0m0.017s
  </code></pre>
  
  <p>Here is the program code:</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;map&gt;
  
  void func_a() {
      std::map&lt;int, int&gt; m;
      for (unsigned int i = 0; i &lt; 10000; i++) {
          m.insert(std::pair&lt;int, int&gt;(i, i));
      }
  }
  
  void func_b() {
      std::map&lt;int, int&gt; m;
      for (unsigned int i = 0; i &lt; 1000000; i++) {
          m.insert(std::pair&lt;int, int&gt;(i, i));
      }
  }
  
  int main() {
      func_a();
      func_b();
      return 0;
  }
  </code></pre>