title: What is the general syntax of a Unix shell command?
body: <p>In particular, why is that sometimes the options to some commands are preceded by a <code>+</code> sign and sometimes by a <code>-</code> sign?</p>
  
  <p>for example:</p>
  
  <pre><code>sort -f
  sort -nr
  sort +4n
  sort +3nr
  </code></pre>