title: What is the written-out word for O_EXCL
body: <p>I was writing a safe <code>enum class</code> for the different file flags listed in <code>open(3)</code>, when I noticed that I couldn't find the written-out word for <code>O_EXCL</code>.</p>
  
  <pre><code>enum class Flags {
      readOnly, // O_RDONLY
      truncate, // O_TRUNC
      ?         // O_EXCL
  };
  </code></pre>
  
  <p>Two possible meanings come into my mind:</p>
  
  <ul>
  <li><code>OPEN_EXCLUSIVE</code></li>
  <li><code>OPEN_EXISTS_CLOSE</code></li>
  </ul>
  
  <p>But I can't find any resources on the intended meaning.</p>