title: Simple way to validate command line arguments
body: <p>How to check if argv (argument vector) contains a char, i.e.: A-Z</p>
  
  <p>Would like to make sure that argv only contains unsigned intergers</p>
  
  <p>For example:</p>
  
  <pre><code>if argv[1] contained "7abc7\0" - ERROR
  
  if argv[1] contains "1234\0" - OK
  </code></pre>