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gobyexample/public/file-paths
Hana 9e216da9ef go.mod: add go.mod and move pygments to third_party 
After go1.16, go will use module mode by default,
even when the repository is checked out under GOPATH
or in a one-off directory. Add go.mod, go.sum to keep
this repo buildable without opting out of the module
mode.

> go mod init github.com/mmcgrana/gobyexample
> go mod tidy
> go mod vendor

In module mode, the 'vendor' directory is special
and its contents will be actively maintained by the
go command. pygments aren't the dependency the go will
know about, so it will delete the contents from vendor
directory. Move it to `third_party` directory now.

And, vendor the blackfriday package.

Note: the tutorial contents are not affected by the
change in go1.16 because all the examples in this
tutorial ask users to run the go command with the
explicit list of files to be compiled (e.g.
`go run hello-world.go` or `go build command-line-arguments.go`).
When the source list is provided, the go command does
not have to compute the build list and whether it's
running in GOPATH mode or module mode becomes irrelevant.
2021-02-15 16:45:26 -05:00

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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example: File Paths</title>
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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" />
<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
<span class="s">&quot;fmt&quot;</span>
<span class="s">&quot;path/filepath&quot;</span>
<span class="s">&quot;strings&quot;</span>
<span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
</pre></div>
</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">
<div class="highlight"><pre> <span class="nx">p</span> <span class="o">:=</span> <span class="nx">filepath</span><span class="p">.</span><span class="nx">Join</span><span class="p">(</span><span class="s">&quot;dir1&quot;</span><span class="p">,</span> <span class="s">&quot;dir2&quot;</span><span class="p">,</span> <span class="s">&quot;filename&quot;</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;p:&quot;</span><span class="p">,</span> <span class="nx">p</span><span class="p">)</span>
</pre></div>
</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">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">filepath</span><span class="p">.</span><span class="nx">Join</span><span class="p">(</span><span class="s">&quot;dir1//&quot;</span><span class="p">,</span> <span class="s">&quot;filename&quot;</span><span class="p">))</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">filepath</span><span class="p">.</span><span class="nx">Join</span><span class="p">(</span><span class="s">&quot;dir1/../dir1&quot;</span><span class="p">,</span> <span class="s">&quot;filename&quot;</span><span class="p">))</span>
</pre></div>
</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">
<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">&quot;Dir(p):&quot;</span><span class="p">,</span> <span class="nx">filepath</span><span class="p">.</span><span class="nx">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="nx">Println</span><span class="p">(</span><span class="s">&quot;Base(p):&quot;</span><span class="p">,</span> <span class="nx">filepath</span><span class="p">.</span><span class="nx">Base</span><span class="p">(</span><span class="nx">p</span><span class="p">))</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>We can check whether a path is absolute.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">filepath</span><span class="p">.</span><span class="nx">IsAbs</span><span class="p">(</span><span class="s">&quot;dir/file&quot;</span><span class="p">))</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">filepath</span><span class="p">.</span><span class="nx">IsAbs</span><span class="p">(</span><span class="s">&quot;/dir/file&quot;</span><span class="p">))</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">filename</span> <span class="o">:=</span> <span class="s">&quot;config.json&quot;</span>
</pre></div>
</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">
<div class="highlight"><pre> <span class="nx">ext</span> <span class="o">:=</span> <span class="nx">filepath</span><span class="p">.</span><span class="nx">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="nx">Println</span><span class="p">(</span><span class="nx">ext</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>To find the file&rsquo;s name with the extension removed,
use <code>strings.TrimSuffix</code>.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">strings</span><span class="p">.</span><span class="nx">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></div>
</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">
<div class="highlight"><pre> <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="nx">Rel</span><span class="p">(</span><span class="s">&quot;a/b&quot;</span><span class="p">,</span> <span class="s">&quot;a/b/t/file&quot;</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="nx">Println</span><span class="p">(</span><span class="nx">rel</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code">
<div class="highlight"><pre> <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="nx">Rel</span><span class="p">(</span><span class="s">&quot;a/b&quot;</span><span class="p">,</span> <span class="s">&quot;a/c/t/file&quot;</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="nx">Println</span><span class="p">(</span><span class="nx">rel</span><span class="p">)</span>
<span class="p">}</span>
</pre></div>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code">
<div class="highlight"><pre><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></div>
</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> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/file-paths">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
</p>
</div>
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