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<section id="common-gotchas">
<h1>Common Gotchas<a class="headerlink" href="#common-gotchas" title="Permalink to this heading">¶</a></h1>
<p>This chapter lists some common gotchas that should be avoided.</p>
<section id="removing-inodes-in-unlink-handler">
<h2>Removing inodes in unlink handler<a class="headerlink" href="#removing-inodes-in-unlink-handler" title="Permalink to this heading">¶</a></h2>
<p>If your file system is mounted at <code class="file docutils literal notranslate"><span class="pre">mnt</span></code>, the following code
should complete without errors:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="k">with</span> <span class="nb">open</span><span class="p">(</span><span class="s1">'mnt/file_one'</span><span class="p">,</span> <span class="s1">'w+'</span><span class="p">)</span> <span class="k">as</span> <span class="n">fh1</span><span class="p">:</span>
<span class="n">fh1</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'foo'</span><span class="p">)</span>
<span class="n">fh1</span><span class="o">.</span><span class="n">flush</span><span class="p">()</span>
<span class="k">with</span> <span class="nb">open</span><span class="p">(</span><span class="s1">'mnt/file_one'</span><span class="p">,</span> <span class="s1">'a'</span><span class="p">)</span> <span class="k">as</span> <span class="n">fh2</span><span class="p">:</span>
<span class="n">os</span><span class="o">.</span><span class="n">unlink</span><span class="p">(</span><span class="s1">'mnt/file_one'</span><span class="p">)</span>
<span class="k">assert</span> <span class="s1">'file_one'</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">os</span><span class="o">.</span><span class="n">listdir</span><span class="p">(</span><span class="s1">'mnt'</span><span class="p">)</span>
<span class="n">fh2</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'bar'</span><span class="p">)</span>
<span class="n">os</span><span class="o">.</span><span class="n">close</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">dup</span><span class="p">(</span><span class="n">fh1</span><span class="o">.</span><span class="n">fileno</span><span class="p">()))</span>
<span class="n">fh1</span><span class="o">.</span><span class="n">seek</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span>
<span class="k">assert</span> <span class="n">fh1</span><span class="o">.</span><span class="n">read</span><span class="p">()</span> <span class="o">==</span> <span class="s1">'foobar'</span>
</pre></div>
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<p>If you’re getting an error, then you probably did a mistake when
implementing the <a class="reference internal" href="operations.html#pyfuse3.Operations.unlink" title="pyfuse3.Operations.unlink"><code class="xref py py-obj docutils literal notranslate"><span class="pre">unlink</span></code></a> handler and are removing the
file contents when you should be deferring removal to the
<a class="reference internal" href="operations.html#pyfuse3.Operations.forget" title="pyfuse3.Operations.forget"><code class="xref py py-obj docutils literal notranslate"><span class="pre">forget</span></code></a> handler.</p>
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