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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example: File Paths</title>
<link rel=stylesheet href="site.css">
</head>
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<body>
<div class="example" id="file-paths">
<h2><a href="./">Go by Example</a>: File Paths</h2>
<table>
<tr>
<td class="docs">
<p>The <code>filepath</code> package provides functions to parse
and construct <em>file paths</em> in a way that is portable
between operating systems; <code>dir/file</code> on Linux vs.
<code>dir\file</code> on Windows, for example.</p>
</td>
<td class="code leading">
<a href="http://play.golang.org/p/5h3lUytvmyO"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<pre class="chroma">
<span class="kn">package</span> <span class="nx">main</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kn">import</span> <span class="p">(</span>
<span class="s">"fmt"</span>
<span class="s">"path/filepath"</span>
<span class="s">"strings"</span>
<span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>Join</code> should be used to construct paths in a
portable way. It takes any number of arguments
and constructs a hierarchical path from them.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">p</span> <span class="o">:=</span> <span class="nx">filepath</span><span class="p">.</span><span class="nf">Join</span><span class="p">(</span><span class="s">"dir1"</span><span class="p">,</span> <span class="s">"dir2"</span><span class="p">,</span> <span class="s">"filename"</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"p:"</span><span class="p">,</span> <span class="nx">p</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>You should always use <code>Join</code> instead of
concatenating <code>/</code>s or <code>\</code>s manually. In addition
to providing portability, <code>Join</code> will also
normalize paths by removing superfluous separators
and directory changes.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">filepath</span><span class="p">.</span><span class="nf">Join</span><span class="p">(</span><span class="s">"dir1//"</span><span class="p">,</span> <span class="s">"filename"</span><span class="p">))</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">filepath</span><span class="p">.</span><span class="nf">Join</span><span class="p">(</span><span class="s">"dir1/../dir1"</span><span class="p">,</span> <span class="s">"filename"</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>Dir</code> and <code>Base</code> can be used to split a path to the
directory and the file. Alternatively, <code>Split</code> will
return both in the same call.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"Dir(p):"</span><span class="p">,</span> <span class="nx">filepath</span><span class="p">.</span><span class="nf">Dir</span><span class="p">(</span><span class="nx">p</span><span class="p">))</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"Base(p):"</span><span class="p">,</span> <span class="nx">filepath</span><span class="p">.</span><span class="nf">Base</span><span class="p">(</span><span class="nx">p</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>We can check whether a path is absolute.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">filepath</span><span class="p">.</span><span class="nf">IsAbs</span><span class="p">(</span><span class="s">"dir/file"</span><span class="p">))</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">filepath</span><span class="p">.</span><span class="nf">IsAbs</span><span class="p">(</span><span class="s">"/dir/file"</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"> <span class="nx">filename</span> <span class="o">:=</span> <span class="s">"config.json"</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>Some file names have extensions following a dot. We
can split the extension out of such names with <code>Ext</code>.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">ext</span> <span class="o">:=</span> <span class="nx">filepath</span><span class="p">.</span><span class="nf">Ext</span><span class="p">(</span><span class="nx">filename</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">ext</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>To find the file’s name with the extension removed,
use <code>strings.TrimSuffix</code>.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">strings</span><span class="p">.</span><span class="nf">TrimSuffix</span><span class="p">(</span><span class="nx">filename</span><span class="p">,</span> <span class="nx">ext</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>Rel</code> finds a relative path between a <em>base</em> and a
<em>target</em>. It returns an error if the target cannot
be made relative to base.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">rel</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">filepath</span><span class="p">.</span><span class="nf">Rel</span><span class="p">(</span><span class="s">"a/b"</span><span class="p">,</span> <span class="s">"a/b/t/file"</span><span class="p">)</span>
<span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
<span class="nb">panic</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="p">}</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">rel</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code">
<pre class="chroma"> <span class="nx">rel</span><span class="p">,</span> <span class="nx">err</span> <span class="p">=</span> <span class="nx">filepath</span><span class="p">.</span><span class="nf">Rel</span><span class="p">(</span><span class="s">"a/b"</span><span class="p">,</span> <span class="s">"a/c/t/file"</span><span class="p">)</span>
<span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
<span class="nb">panic</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="p">}</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">rel</span><span class="p">)</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code">
<pre class="chroma"><span class="gp">$</span> go run file-paths.go
<span class="go">p: dir1/dir2/filename
</span><span class="go">dir1/filename
</span><span class="go">dir1/filename
</span><span class="go">Dir(p): dir1/dir2
</span><span class="go">Base(p): filename
</span><span class="go">false
</span><span class="go">true
</span><span class="go">.json
</span><span class="go">config
</span><span class="go">t/file
</span><span class="go">../c/t/file</span></pre>
</td>
</tr>
</table>
<p class="next">
Next example: <a href="directories">Directories</a>.
</p>
<p class="footer">
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> and <a href="https://eli.thegreenplace.net">Eli Bendersky</a> | <a href="https://github.com/mmcgrana/gobyexample">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
</p>
</div>
<script>
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