title: use a shell script to update version
body: <pre><code>#include  "calcmarks.h"
  
  // calcmarks, version 1, released Thu Mar 23 13:16:49 WST 2017
  
  int main(int argc, char *argv[])
  {
      int nmarks = 0;
  
      if(argc == 1) {
           nmarks += readmarks(stdin);
  </code></pre>
  
  <p>Don't care what this code is, what I want is a shellscript to update and version.After do the shellscript,the comment above will become</p>
  
  <p>// calcmarks, version 2, released (time you execute the script)</p>
  
  <p>Tried to do below which didn't work.</p>
  
  <pre><code>a=$(date) 
  sed -i "_bak" s'/Thu Mar 23 13:16:49 WST 2017/$a/g' "calcmarks.c"
  </code></pre>