361 lines
17 KiB
Plaintext
Generated
361 lines
17 KiB
Plaintext
Generated
<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Go by Example: Directories</title>
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<link rel=stylesheet href="site.css">
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</head>
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<script>
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onkeydown = (e) => {
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if (e.key == "ArrowLeft") {
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window.location.href = 'file-paths';
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}
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if (e.key == "ArrowRight") {
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window.location.href = 'temporary-files-and-directories';
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}
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}
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</script>
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<body>
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<div class="example" id="directories">
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<h2><a href="./">Go by Example</a>: Directories</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Go has several useful functions for working with
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<em>directories</em> in the file system.</p>
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</td>
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<td class="code empty leading">
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</td>
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<td class="docs">
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</td>
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<td class="code leading">
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<a href="http://play.golang.org/p/UaeLMS5VQVR"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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</pre></div>
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</td>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
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<span class="s">"fmt"</span>
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<span class="s">"io/ioutil"</span>
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<span class="s">"os"</span>
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<span class="s">"path/filepath"</span>
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<span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">check</span><span class="p">(</span><span class="nx">e</span> <span class="kt">error</span><span class="p">)</span> <span class="p">{</span>
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<span class="k">if</span> <span class="nx">e</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
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<span class="nb">panic</span><span class="p">(</span><span class="nx">e</span><span class="p">)</span>
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<span class="p">}</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Create a new sub-directory in the current working
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directory.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">os</span><span class="p">.</span><span class="nx">Mkdir</span><span class="p">(</span><span class="s">"subdir"</span><span class="p">,</span> <span class="mo">0755</span><span class="p">)</span>
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<span class="nx">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>When creating temporary directories, it’s good
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practice to <code>defer</code> their removal. <code>os.RemoveAll</code>
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will delete a whole directory tree (similarly to
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<code>rm -rf</code>).</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="k">defer</span> <span class="nx">os</span><span class="p">.</span><span class="nx">RemoveAll</span><span class="p">(</span><span class="s">"subdir"</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<td class="docs">
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<p>Helper function to create a new empty file.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">createEmptyFile</span> <span class="o">:=</span> <span class="kd">func</span><span class="p">(</span><span class="nx">name</span> <span class="kt">string</span><span class="p">)</span> <span class="p">{</span>
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<span class="nx">d</span> <span class="o">:=</span> <span class="p">[]</span><span class="nb">byte</span><span class="p">(</span><span class="s">""</span><span class="p">)</span>
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<span class="nx">check</span><span class="p">(</span><span class="nx">ioutil</span><span class="p">.</span><span class="nx">WriteFile</span><span class="p">(</span><span class="nx">name</span><span class="p">,</span> <span class="nx">d</span><span class="p">,</span> <span class="mo">0644</span><span class="p">))</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">createEmptyFile</span><span class="p">(</span><span class="s">"subdir/file1"</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>We can create a hierarchy of directories, including
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parents with <code>MkdirAll</code>. This is similar to the
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command-line <code>mkdir -p</code>.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">err</span> <span class="p">=</span> <span class="nx">os</span><span class="p">.</span><span class="nx">MkdirAll</span><span class="p">(</span><span class="s">"subdir/parent/child"</span><span class="p">,</span> <span class="mo">0755</span><span class="p">)</span>
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<span class="nx">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">createEmptyFile</span><span class="p">(</span><span class="s">"subdir/parent/file2"</span><span class="p">)</span>
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<span class="nx">createEmptyFile</span><span class="p">(</span><span class="s">"subdir/parent/file3"</span><span class="p">)</span>
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<span class="nx">createEmptyFile</span><span class="p">(</span><span class="s">"subdir/parent/child/file4"</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p><code>ReadDir</code> lists directory contents, returning a
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slice of <code>os.FileInfo</code> objects.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">c</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">ioutil</span><span class="p">.</span><span class="nx">ReadDir</span><span class="p">(</span><span class="s">"subdir/parent"</span><span class="p">)</span>
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<span class="nx">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"Listing subdir/parent"</span><span class="p">)</span>
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<span class="k">for</span> <span class="nx">_</span><span class="p">,</span> <span class="nx">entry</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">c</span> <span class="p">{</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">" "</span><span class="p">,</span> <span class="nx">entry</span><span class="p">.</span><span class="nx">Name</span><span class="p">(),</span> <span class="nx">entry</span><span class="p">.</span><span class="nx">IsDir</span><span class="p">())</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p><code>Chdir</code> lets us change the current working directory,
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similarly to <code>cd</code>.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">err</span> <span class="p">=</span> <span class="nx">os</span><span class="p">.</span><span class="nx">Chdir</span><span class="p">(</span><span class="s">"subdir/parent/child"</span><span class="p">)</span>
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<span class="nx">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Now we’ll see the contents of <code>subdir/parent/child</code>
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when listing the <em>current</em> directory.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">c</span><span class="p">,</span> <span class="nx">err</span> <span class="p">=</span> <span class="nx">ioutil</span><span class="p">.</span><span class="nx">ReadDir</span><span class="p">(</span><span class="s">"."</span><span class="p">)</span>
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<span class="nx">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"Listing subdir/parent/child"</span><span class="p">)</span>
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<span class="k">for</span> <span class="nx">_</span><span class="p">,</span> <span class="nx">entry</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">c</span> <span class="p">{</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">" "</span><span class="p">,</span> <span class="nx">entry</span><span class="p">.</span><span class="nx">Name</span><span class="p">(),</span> <span class="nx">entry</span><span class="p">.</span><span class="nx">IsDir</span><span class="p">())</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p><code>cd</code> back to where we started.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">err</span> <span class="p">=</span> <span class="nx">os</span><span class="p">.</span><span class="nx">Chdir</span><span class="p">(</span><span class="s">"../../.."</span><span class="p">)</span>
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<span class="nx">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>We can also visit a directory <em>recursively</em>,
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including all its sub-directories. <code>Walk</code> accepts
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a callback function to handle every file or
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directory visited.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"Visiting subdir"</span><span class="p">)</span>
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<span class="nx">err</span> <span class="p">=</span> <span class="nx">filepath</span><span class="p">.</span><span class="nx">Walk</span><span class="p">(</span><span class="s">"subdir"</span><span class="p">,</span> <span class="nx">visit</span><span class="p">)</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p><code>visit</code> is called for every file or directory found
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recursively by <code>filepath.Walk</code>.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">visit</span><span class="p">(</span><span class="nx">p</span> <span class="kt">string</span><span class="p">,</span> <span class="nx">info</span> <span class="nx">os</span><span class="p">.</span><span class="nx">FileInfo</span><span class="p">,</span> <span class="nx">err</span> <span class="kt">error</span><span class="p">)</span> <span class="kt">error</span> <span class="p">{</span>
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<span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
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<span class="k">return</span> <span class="nx">err</span>
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<span class="p">}</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">" "</span><span class="p">,</span> <span class="nx">p</span><span class="p">,</span> <span class="nx">info</span><span class="p">.</span><span class="nx">IsDir</span><span class="p">())</span>
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<span class="k">return</span> <span class="kc">nil</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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</table>
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<table>
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<tr>
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<td class="docs">
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</td>
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<td class="code">
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<div class="highlight"><pre><span class="gp">$</span> go run directories.go
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<span class="go">Listing subdir/parent</span>
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<span class="go"> child true</span>
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<span class="go"> file2 false</span>
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<span class="go"> file3 false</span>
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<span class="go">Listing subdir/parent/child</span>
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<span class="go"> file4 false</span>
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<span class="go">Visiting subdir</span>
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<span class="go"> subdir true</span>
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<span class="go"> subdir/file1 false</span>
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<span class="go"> subdir/parent true</span>
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<span class="go"> subdir/parent/child true</span>
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<span class="go"> subdir/parent/child/file4 false</span>
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<span class="go"> subdir/parent/file2 false</span>
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<span class="go"> subdir/parent/file3 false</span>
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</pre></div>
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</td>
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</tr>
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</table>
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<p class="next">
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Next example: <a href="temporary-files-and-directories">Temporary Files and Directories</a>.
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</p>
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<p class="footer">
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by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/directories">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
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</p>
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</div>
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<script>
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var codeLines = [];
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codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import (\u000A \"fmt\"\u000A \"io/ioutil\"\u000A \"os\"\u000A \"path/filepath\"\u000A)\u000A');codeLines.push('func check(e error) {\u000A if e !\x3D nil {\u000A panic(e)\u000A }\u000A}\u000A');codeLines.push('func main() {\u000A');codeLines.push(' err :\x3D os.Mkdir(\"subdir\", 0755)\u000A check(err)\u000A');codeLines.push(' defer os.RemoveAll(\"subdir\")\u000A');codeLines.push(' createEmptyFile :\x3D func(name string) {\u000A d :\x3D []byte(\"\")\u000A check(ioutil.WriteFile(name, d, 0644))\u000A }\u000A');codeLines.push(' createEmptyFile(\"subdir/file1\")\u000A');codeLines.push(' err \x3D os.MkdirAll(\"subdir/parent/child\", 0755)\u000A check(err)\u000A');codeLines.push(' createEmptyFile(\"subdir/parent/file2\")\u000A createEmptyFile(\"subdir/parent/file3\")\u000A createEmptyFile(\"subdir/parent/child/file4\")\u000A');codeLines.push(' c, err :\x3D ioutil.ReadDir(\"subdir/parent\")\u000A check(err)\u000A');codeLines.push(' fmt.Println(\"Listing subdir/parent\")\u000A for _, entry :\x3D range c {\u000A fmt.Println(\" \", entry.Name(), entry.IsDir())\u000A }\u000A');codeLines.push(' err \x3D os.Chdir(\"subdir/parent/child\")\u000A check(err)\u000A');codeLines.push(' c, err \x3D ioutil.ReadDir(\".\")\u000A check(err)\u000A');codeLines.push(' fmt.Println(\"Listing subdir/parent/child\")\u000A for _, entry :\x3D range c {\u000A fmt.Println(\" \", entry.Name(), entry.IsDir())\u000A }\u000A');codeLines.push(' err \x3D os.Chdir(\"../../..\")\u000A check(err)\u000A');codeLines.push(' fmt.Println(\"Visiting subdir\")\u000A err \x3D filepath.Walk(\"subdir\", visit)\u000A}\u000A');codeLines.push('func visit(p string, info os.FileInfo, err error) error {\u000A if err !\x3D nil {\u000A return err\u000A }\u000A fmt.Println(\" \", p, info.IsDir())\u000A return nil\u000A}\u000A');codeLines.push('');
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<script src="site.js" async></script>
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</body>
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