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writing-files.html
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example 中文版: 写文件</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'reading-files';
}
if (e.key == "ArrowRight") {
window.location.href = 'line-filters';
}
}
</script>
<body>
<div class="example" id="writing-files">
<h2><a href="./">Go by Example 中文版</a>: 写文件</h2>
<table>
<tr>
<td class="docs">
<p>在 Go 中，写文件与我们前面看过的读文件方法类似。</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="https://play.studygolang.com/p/2CEMRivZzqA"><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">"bufio"</span>
<span class="s">"fmt"</span>
<span class="s">"os"</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">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>
</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>开始！这里展示了如何写入一个字符串（或者只是一些字节）到一个文件。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">d1</span> <span class="o">:=</span> <span class="p">[]</span><span class="nb">byte</span><span class="p">(</span><span class="s">"hello\ngo\n"</span><span class="p">)</span>
<span class="nx">err</span> <span class="o">:=</span> <span class="nx">os</span><span class="p">.</span><span class="nf">WriteFile</span><span class="p">(</span><span class="s">"/tmp/dat1"</span><span class="p">,</span> <span class="nx">d1</span><span class="p">,</span> <span class="mo">0644</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>对于更细粒度的写入，先打开一个文件。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">f</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">os</span><span class="p">.</span><span class="nf">Create</span><span class="p">(</span><span class="s">"/tmp/dat2"</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>打开文件后，一个习惯性的操作是：立即使用 defer 调用文件的 <code>Close</code>。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="k">defer</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Close</span><span class="p">()</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>您可以按期望的那样 <code>Write</code> 字节切片。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">d2</span> <span class="o">:=</span> <span class="p">[]</span><span class="kt">byte</span><span class="p">{</span><span class="mi">115</span><span class="p">,</span> <span class="mi">111</span><span class="p">,</span> <span class="mi">109</span><span class="p">,</span> <span class="mi">101</span><span class="p">,</span> <span class="mi">10</span><span class="p">}</span>
<span class="nx">n2</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">Write</span><span class="p">(</span><span class="nx">d2</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"wrote %d bytes\n"</span><span class="p">,</span> <span class="nx">n2</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>WriteString</code> 也是可用的。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">n3</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">f</span><span class="p">.</span><span class="nf">WriteString</span><span class="p">(</span><span class="s">"writes\n"</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"wrote %d bytes\n"</span><span class="p">,</span> <span class="nx">n3</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>调用 <code>Sync</code> 将缓冲区的数据写入硬盘。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">f</span><span class="p">.</span><span class="nf">Sync</span><span class="p">()</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>与我们前面看到的带缓冲的 Reader 一样，<code>bufio</code> 还提供了的带缓冲的 Writer。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">w</span> <span class="o">:=</span> <span class="nx">bufio</span><span class="p">.</span><span class="nf">NewWriter</span><span class="p">(</span><span class="nx">f</span><span class="p">)</span>
<span class="nx">n4</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">w</span><span class="p">.</span><span class="nf">WriteString</span><span class="p">(</span><span class="s">"buffered\n"</span><span class="p">)</span>
<span class="nf">check</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Printf</span><span class="p">(</span><span class="s">"wrote %d bytes\n"</span><span class="p">,</span> <span class="nx">n4</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>使用 <code>Flush</code> 来确保，已将所有的缓冲操作应用于底层 writer。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">w</span><span class="p">.</span><span class="nf">Flush</span><span class="p">()</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code">
<pre class="chroma"><span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
<p>运行这段文件写入代码。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="gp">$</span> go run writing-files.go
<span class="go">wrote 5 bytes
</span><span class="go">wrote 7 bytes
</span><span class="go">wrote 9 bytes</span></pre>
</td>
</tr>
<tr>
<td class="docs">
<p>然后检查写入文件的内容。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="gp">$</span> cat /tmp/dat1
<span class="go">hello
</span><span class="go">go
</span><span class="go"></span><span class="gp">$</span> cat /tmp/dat2
<span class="go">some
</span><span class="go">writes
</span><span class="go">buffered</span></pre>
</td>
</tr>
<tr>
<td class="docs">
<p>我们刚刚看到了文件 I/O 思想，
接下来，我们看看它在 <code>stdin</code> 和 <code>stdout</code> 流中的应用。</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<p class="next">
下一个例子: <a href="line-filters">行过滤器</a>
</p>
<p class="footer">
<a href="https://twitter.com/mmcgrana">@mmcgrana</a> 和<a href="https://eli.thegreenplace.net">Eli Bendersky</a>编写 | <a href="https://github.com/gobyexample-cn">gobyexample-cn</a> 翻译 | <a href="https://github.com/gobyexample-cn/gobyexample/issues">反馈</a> | <a href="https://github.com/gobyexample-cn/gobyexample">源码</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a> </p>
</p>
</div>
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