title: Writing FS with FUSE, function not implemented error when `cat>a`
body: <p>I'm writing FS with FUSE, here are the functions I've implemented: </p>
  
  <p><code>create</code> <code>open</code> <code>read</code> <code>write</code> <code>release</code> <code>unlink</code> <code>mkdir</code> <code>opendir</code> <code>readdir</code> <code>releasedir</code> <code>rmdir</code> <code>getattr</code> <code>rename</code></p>
  
  <p>Everything works fine, except this case: when I first try <code>cat&gt;a</code> (when a file still does not exist) it works fine: creates "a" and lets me write something in it.</p>
  
  <p>But when I type again <code>cat&gt;a</code> It tells me <code>-bash: a: Function not implemented</code>. (Similar message appears when I try to modify file with <code>nano a</code> it opens let's me write in, but after trying to save modifications the same message appears in <code>nano</code>)</p>
  
  <p>What can be the cause? Which function may I me missing? Or which function may be implemented not properly?</p>