title: What does the 'x' mean in rwx on a directory?
body: <p>I got a testdir by <code>mkdir testdir</code>, and created a file in it by <code>touch testdir/a</code>.</p>
  
  <pre><code>drwxr-xr-x  2 jermaine     jermaine       4096 Mar 12 22:57 testdir
  </code></pre>
  
  <p>If I remove the 'x' by <code>chmod -x testdir</code></p>
  
  <p>Then I won't be able to </p>
  
  <pre><code>cd testdir
  
  touch testdir/b
  
  ls -l testdir
  
  cat testdir/a
  </code></pre>
  
  <p>So my question is why can't I list the file hierarchy under a directory with a 'r' but without an 'x'? What exactly does the 'x' mean on directory? </p>
  
  <p>I knew some explanations like "x means entering the direcotry, you have to enter before read and write". But what does 'enter' mean? I really appreciate answers on inode or dentry level. Thanks a lot.</p>