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Add directories example

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Eli Bendersky 2019-06-08 06:11:13 -07:00
parent 6eae6fe9b7
commit 447d77234f
7 changed files with 387 additions and 1 deletions
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1
examples.txt
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@ -58,6 +58,7 @@ Reading Files
Writing Files Writing Files
Line Filters Line Filters
File Paths File Paths
Directories
Command-Line Arguments Command-Line Arguments
Command-Line Flags Command-Line Flags
Command-Line Subcommands Command-Line Subcommands

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examples/directories/directories.go Normal file
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// Go has several useful functions for working with
// *directories* in the file system.
package main
import (
"fmt"
"io/ioutil"
"os"
)
func check(e error) {
if e != nil {
panic(e)
}
}
func main() {
// Create a new sub-directory in the current working
// directory.
err := os.Mkdir("subdir", 0755)
check(err)
// When creating temporary directories, it's good
// practice to `defer` their removal. `os.RemoveAll`
// will delete a whole directory tree (similarly to
// `rm -rf`).
defer os.RemoveAll("subdir")
// Helper function to create a new empty file.
createEmptyFile := func(name string) {
d := []byte("")
check(ioutil.WriteFile(name, d, 0644))
}
createEmptyFile("subdir/file1")
// We can create a hierarchy of directories, including
// parents wiht `MkdirAll`. This is similar to the
// command-line `mkdir -p`.
err = os.MkdirAll("subdir/parent/child", 0755)
check(err)
createEmptyFile("subdir/parent/file2")
createEmptyFile("subdir/parent/file3")
createEmptyFile("subdir/parent/child/file4")
// `ReadDir` lists directory contents, returning a
// slice of `os.FileInfo` objects.
c, err := ioutil.ReadDir("subdir/parent")
check(err)
fmt.Println("Listing subdir/parent")
for _, entry := range c {
fmt.Println(entry.Name(), entry.IsDir())
}
// `Chdir` lets us change the current working directory,
// similarly to `cd`.
err = os.Chdir("subdir/parent/child")
check(err)
// Now we'll see the contents of "subdir/parent/child"
// when listing the *current* directory.
c, err = ioutil.ReadDir(".")
check(err)
fmt.Println("Listing subdir/parent/child")
for _, entry := range c {
fmt.Println(entry.Name(), entry.IsDir())
}
// `cd` back to where we started.
err = os.Chdir("../../..")
check(err)
}

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examples/directories/directories.hash Normal file
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7b2eed223a00c8a84df582bd254a642c7a57dd9b
UnjBL6NmR8-

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examples/directories/directories.sh Normal file
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$ go run directories.go
Listing subdir/parent
child true
file2 false
file3 false
Listing subdir/parent/child
file4 false

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public/directories Normal file
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example: Directories</title>
<link rel=stylesheet href="site.css">
</head>
<body>
<div class="example" id="directories">
<h2><a href="./">Go by Example</a>: Directories</h2>
<table>
<tr>
<td class="docs">
<p>Go has several useful functions for working with
<em>directories</em> in the file system.</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="http://play.golang.org/p/UnjBL6NmR8-">
<img title="Run code" class="run" src="data:image/png;base64,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" />
</a>
<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;io/ioutil&quot;</span>
<span class="s">&quot;os&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">check</span><span class="p">(</span><span class="nx">e</span> <span class="kt">error</span><span class="p">)</span> <span class="p">{</span>
<span class="k">if</span> <span class="nx">e</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">e</span><span class="p">)</span>
<span class="p">}</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>Create a new sub-directory in the current working
directory.</p>
</td>
<td class="code leading">
<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">&quot;subdir&quot;</span><span class="p">,</span> <span class="mo">0755</span><span class="p">)</span>
<span class="nx">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>When creating temporary directories, it&rsquo;s good
practice to <code>defer</code> their removal. <code>os.RemoveAll</code>
will delete a whole directory tree (similarly to
<code>rm -rf</code>).</p>
</td>
<td class="code leading">
<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">&quot;subdir&quot;</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>Helper function to create a new empty file.</p>
</td>
<td class="code leading">
<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>
<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">&quot;&quot;</span><span class="p">)</span>
<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>
<span class="p">}</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">createEmptyFile</span><span class="p">(</span><span class="s">&quot;subdir/file1&quot;</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>We can create a hierarchy of directories, including
parents wiht <code>MkdirAll</code>. This is similar to the
command-line <code>mkdir -p</code>.</p>
</td>
<td class="code leading">
<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">&quot;subdir/parent/child&quot;</span><span class="p">,</span> <span class="mo">0755</span><span class="p">)</span>
<span class="nx">check</span><span class="p">(</span><span class="nx">err</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">createEmptyFile</span><span class="p">(</span><span class="s">&quot;subdir/parent/file2&quot;</span><span class="p">)</span>
<span class="nx">createEmptyFile</span><span class="p">(</span><span class="s">&quot;subdir/parent/file3&quot;</span><span class="p">)</span>
<span class="nx">createEmptyFile</span><span class="p">(</span><span class="s">&quot;subdir/parent/child/file4&quot;</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p><code>ReadDir</code> lists directory contents, returning a
slice of <code>os.FileInfo</code> objects.</p>
</td>
<td class="code leading">
<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">&quot;subdir/parent&quot;</span><span class="p">)</span>
<span class="nx">check</span><span class="p">(</span><span class="nx">err</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">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;Listing subdir/parent&quot;</span><span class="p">)</span>
<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>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</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>
<span class="p">}</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p><code>Chdir</code> lets us change the current working directory,
similarly to <code>cd</code>.</p>
</td>
<td class="code leading">
<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">&quot;subdir/parent/child&quot;</span><span class="p">)</span>
<span class="nx">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>Now we&rsquo;ll see the contents of &ldquo;subdir/parent/child&rdquo;
when listing the <em>current</em> directory.</p>
</td>
<td class="code leading">
<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">&quot;.&quot;</span><span class="p">)</span>
<span class="nx">check</span><span class="p">(</span><span class="nx">err</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">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;Listing subdir/parent/child&quot;</span><span class="p">)</span>
<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>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</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>
<span class="p">}</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p><code>cd</code> back to where we started.</p>
</td>
<td class="code">
<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">&quot;../../..&quot;</span><span class="p">)</span>
<span class="nx">check</span><span class="p">(</span><span class="nx">err</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 directories.go
<span class="go">Listing subdir/parent</span>
<span class="go">child true</span>
<span class="go">file2 false</span>
<span class="go">file3 false</span>
<span class="go">Listing subdir/parent/child</span>
<span class="go">file4 false</span>
</pre></div>
</td>
</tr>
</table>
<p class="next">
Next example: <a href="command-line-arguments">Command-Line Arguments</a>.
</p>
<p class="footer">
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>
</p>
</div>
</body>
</html>

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public/file-paths
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@ -229,7 +229,7 @@ be made relative to base.</p>
<p class="next"> <p class="next">
Next example: <a href="command-line-arguments">Command-Line Arguments</a>. Next example: <a href="directories">Directories</a>.
</p> </p>
<p class="footer"> <p class="footer">

2
public/index.html
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@ -143,6 +143,8 @@
<li><a href="file-paths">File Paths</a></li> <li><a href="file-paths">File Paths</a></li>
<li><a href="directories">Directories</a></li>
<li><a href="command-line-arguments">Command-Line Arguments</a></li> <li><a href="command-line-arguments">Command-Line Arguments</a></li>
<li><a href="command-line-flags">Command-Line Flags</a></li> <li><a href="command-line-flags">Command-Line Flags</a></li>