title: How to compute run time for a C program in ubuntu
body: <p>I tried <code>&gt;&gt;time ./a.out</code></p>
  
  <p>got</p>
  
  <pre><code>real 0m0.035s
  
  user 0m0.008s
  
  sys  0m0.004s
  </code></pre>
  
  <p>what it really means?</p>
  
  <p>when I repeated I got</p>
  
  <pre><code>real 0m0.012s
  
  user 0m0.000s
  
  sys  0m0.012s
  </code></pre>
  
  <p>if I try this many times 
  each time I am getting different output why? how can I solve it.</p>