title: grep for lines containing "standard" US characters only
body: <p>I'm trying to figure out how to <code>grep</code> for lines that are made up of A-Z and a-z exclusively, that is, the "American" alphabet of letters. I would expect this to work, but it does not:</p>
  
  <pre><code>$ echo -e "Jutland\nJastrząb" | grep -x '[A-Za-z]*'
  Jutland
  Jastrząb
  </code></pre>
  
  <p>I want this to only print "Jutland", because <strong>ą</strong> is not a letter in the American alphabet. How can I achieve this?</p>