title: Checking for certain characters in C string
body: <p>When accepting command line arguments in C, is there any way to ensure that the string contains only letters (i.e., no <s>letters</s> digits or symbols) without converting to int?  Is there a built-in function for this?</p>
  
  <pre><code>int
  main(int argc, char *argv[])
  {
  
     char *input = argv[1];
     if (/* input contains anything but upper and lowercase letters */)
        return 1;
     ...
  }
  </code></pre>