title: How to use dash (-) with unix commands correctly?
body: <p>I have just noticed that commands:</p>
  <pre><code>ps -T
  </code></pre>
  <p>and</p>
  <pre><code>ps T
  </code></pre>
  <p>give different results. For instance:</p>
  <p><a href="https://i.stack.imgur.com/cQqfs.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cQqfs.png" alt="ps -T" /></a></p>
  <p><a href="https://i.stack.imgur.com/hCIoF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hCIoF.png" alt="ps T" /></a></p>
  <p>I mean lines 2 and 3 of second output. <br>
  Could someone please explain what happens here and how the dash really works in such commands (to be honest I thought options that didn't require an argument could be given without a dash).</p>
  <p>Thanks in advance.</p>