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<p>提供基本语法和方法的 C 快速参考备忘单。</p>
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</svg></div><div class="menu-modal"><a aria-hidden="true" class="leve2 tocs-link" data-num="2" href="#入门">入门</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#helloc">hello.c</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#变量">变量</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#常量-constants">常量 Constants</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#注释">注释</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#打印文本">打印文本</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#控制空格数">控制空格数</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#字符串-strings">字符串 Strings</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#条件判断">条件判断</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#三元运算符">三元运算符</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#switch">Switch</a><a aria-hidden="true" class="leve3 tocs-link" 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href="#基本格式说明符">基本格式说明符</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#基本格式说明符-1">基本格式说明符</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#数据格式示例">数据格式示例</a><a aria-hidden="true" class="leve2 tocs-link" data-num="2" href="#预处理器">预处理器</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#预处理器指令">预处理器指令</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#预定义宏">预定义宏</a><a aria-hidden="true" class="leve4 tocs-link" data-num="4" href="#预定义宏示例">预定义宏示例</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#宏延续运算符">宏延续运算符（\）</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#字符串常量化运算符">字符串常量化运算符（#）</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#标记粘贴运算符">标记粘贴运算符（##）</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#defined-运算符">defined() 运算符</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#参数化的宏">参数化的宏</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#warning-和-error">Warning 和 Error</a><a aria-hidden="true" class="leve2 tocs-link" data-num="2" href="#函数">函数</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#函数声明和定义">函数声明和定义</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#调用函数">调用函数</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#函数参数">函数参数</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#多个参数">多个参数</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#返回值">返回值</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#递归示例">递归示例</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#数学函数">数学函数</a><a aria-hidden="true" class="leve2 tocs-link" data-num="2" href="#structures-结构">Structures 结构</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#创建结构">创建结构</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#结构中的字符串">结构中的字符串</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#访问结构成员">访问结构成员</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#复制结构">复制结构</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#修改值">修改值</a><a aria-hidden="true" class="leve2 tocs-link" data-num="2" href="#文件处理">文件处理</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#文件处理函数">文件处理函数</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#打开模式参数">打开模式参数</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#打开文件fopen">打开文件：fopen()</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#写入文件fprintf">写入文件：fprintf()</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#读取文件fscanf">读取文件：fscanf()</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#写入文件fputc">写入文件：fputc()</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#读取文件fgetc">读取文件：fgetc()</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#写入文件fputs">写入文件：fputs()</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#读取文件fgets">读取文件：fgets()</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#fseek">fseek()</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#rewind">rewind()</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#ftell">ftell()</a><a aria-hidden="true" class="leve2 tocs-link" data-num="2" href="#c-网络编程">C 网络编程</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#网络编程介绍">网络编程介绍</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#创建套接字">创建套接字</a><a aria-hidden="true" class="leve4 tocs-link" data-num="4" href="#服务端">服务端</a><a aria-hidden="true" class="leve4 tocs-link" data-num="4" href="#客户端">客户端</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#绑定套接字">绑定套接字</a><a aria-hidden="true" class="leve4 tocs-link" data-num="4" href="#服务端-1">服务端</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#监听和接收连接">监听和接收连接</a><a aria-hidden="true" class="leve4 tocs-link" data-num="4" href="#服务端-2">服务端</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#连接到服务端">连接到服务端</a><a aria-hidden="true" class="leve4 tocs-link" data-num="4" href="#客户端-1">客户端</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#发送和接收数据">发送和接收数据</a><a aria-hidden="true" class="leve4 tocs-link" data-num="4" href="#服务端-3">服务端</a><a aria-hidden="true" class="leve4 tocs-link" data-num="4" href="#客户端-2">客户端</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#关闭套接字">关闭套接字</a><a aria-hidden="true" class="leve4 tocs-link" data-num="4" href="#服务端-4">服务端</a><a aria-hidden="true" class="leve4 tocs-link" data-num="4" href="#客户端-3">客户端</a><a aria-hidden="true" class="leve2 tocs-link" data-num="2" href="#io多路复用">I/O多路复用</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#多路复用介绍">多路复用介绍</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#使用select">使用select</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#使用poll">使用poll</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#使用epoll">使用epoll</a><a aria-hidden="true" class="leve2 tocs-link" data-num="2" href="#杂项">杂项</a><a aria-hidden="true" class="leve3 tocs-link" data-num="3" href="#docker-运行环境">Docker 运行环境</a><a aria-hidden="true" class="leve2 tocs-link" data-num="2" href="#另见">另见</a></div></div><div class="h1wrap-body"><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="入门"><a aria-hidden="true" tabindex="-1" href="#入门"><span class="icon icon-link"></span></a>入门</h2><div class="wrap-body">
|
||
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="helloc"><a aria-hidden="true" tabindex="-1" href="#helloc"><span class="icon icon-link"></span></a>hello.c</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Hello World!"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
<p>使用 <code>gcc</code> 编译 <code>hello.c</code> 源文件</p>
|
||
<pre class="language-bash"><code class="language-bash code-highlight"><span class="code-line">$ gcc <span class="token parameter variable">-o</span> hello hello.c
|
||
</span></code></pre>
|
||
<p>运行编译后的二进制文件可执行文件(<code>hello</code>)</p>
|
||
<pre class="language-bash"><code class="language-bash code-highlight"><span class="code-line">$ ./hello
|
||
</span><span class="code-line"><span class="token comment"># 输出 => Hello World</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="变量"><a aria-hidden="true" tabindex="-1" href="#变量"><span class="icon icon-link"></span></a>变量</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> myNum <span class="token operator">=</span> <span class="token number">15</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> myNum2<span class="token punctuation">;</span> <span class="token comment">// 声明变量 myNum2</span>
|
||
</span><span class="code-line"><span class="token comment">// 变量声明后第一次赋值我们称为初始化</span>
|
||
</span><span class="code-line"><span class="token comment">// 如果 初始化 和 赋值 在同一行</span>
|
||
</span><span class="code-line"><span class="token comment">// 那么我们可以直接称为 定义变量 myNum2</span>
|
||
</span><span class="code-line">myNum2 <span class="token operator">=</span> <span class="token number">15</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> myNum3 <span class="token operator">=</span> <span class="token number">15</span><span class="token punctuation">;</span> <span class="token comment">// myNum3 值为 15</span>
|
||
</span><span class="code-line">myNum3 <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">;</span> <span class="token comment">// 现在 myNum3 值为 10</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">float</span> myFloatNum <span class="token operator">=</span> <span class="token number">5.99</span><span class="token punctuation">;</span> <span class="token comment">// 浮点数</span>
|
||
</span><span class="code-line"><span class="token keyword">char</span> myLetter <span class="token operator">=</span> <span class="token char">'D'</span><span class="token punctuation">;</span> <span class="token comment">// 字符</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> x <span class="token operator">=</span> <span class="token number">5</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> y <span class="token operator">=</span> <span class="token number">6</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> sum <span class="token operator">=</span> x <span class="token operator">+</span> y<span class="token punctuation">;</span> <span class="token comment">// 添加变量相加</span>
|
||
</span><span class="code-line"><span class="token comment">// 声明多个变量</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> x <span class="token operator">=</span> <span class="token number">5</span><span class="token punctuation">,</span> y <span class="token operator">=</span> <span class="token number">6</span><span class="token punctuation">,</span> z <span class="token operator">=</span> <span class="token number">50</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">//仅声明变量不初始化</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> result<span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 如果未初始化，变量的值是未定义的，使用它会导致错误的结果。</span>
|
||
</span><span class="code-line"><span class="token comment">// 此时，变量的值是随机的，因此在使用该变量之前必须进行初始化。</span>
|
||
</span><span class="code-line">result <span class="token operator">=</span> result <span class="token operator">+</span> <span class="token number">10</span><span class="token punctuation">;</span> <span class="token comment">// 错误：未初始化的变量 result 会导致不可预测的结果</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 部分编译器会输出 Warning，警告未初始化的变量可能导致未定义行为。</span>
|
||
</span><span class="code-line">
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="常量-constants"><a aria-hidden="true" tabindex="-1" href="#常量-constants"><span class="icon icon-link"></span></a>常量 Constants</h3><div class="wrap-body">
|
||
<p>常量在 C 语言中我们一般理解为不能被改变的值，活用常量与符号常量，可以使代码更加清晰和安全</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">const</span> <span class="token keyword">int</span> minutesPerHour <span class="token operator">=</span> <span class="token number">60</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">const</span> <span class="token keyword">float</span> PI <span class="token operator">=</span> <span class="token number">3.14</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
<p>最佳实践</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">const</span> <span class="token keyword">int</span> BIRTHYEAR <span class="token operator">=</span> <span class="token number">1980</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
<p>说明与补充：</p>
|
||
<ol>
|
||
<li>
|
||
<p><strong>常量命名规范</strong>：常量通常使用全大写字母，多个单词之间用下划线分隔（例如 BIRTHYEAR、MAX_LENGTH）。</p>
|
||
</li>
|
||
<li>
|
||
<p><strong><code>#define</code> 与 <code>const</code></strong>：</p>
|
||
<ul>
|
||
<li><strong><code>#define</code></strong>：宏常量通常在预处理阶段进行替换，不进行类型检查；</li>
|
||
<li><strong><code>const</code></strong>：类型安全的常量，编译器可以检查类型，一般更推荐使用 <code>const</code></li>
|
||
</ul>
|
||
</li>
|
||
<li>
|
||
<p><strong>数组大小</strong>：可以使用 <code>const</code> 来定义数组的常量大小，这样编译器会将其作为编译时常量处理</p>
|
||
</li>
|
||
</ol>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="注释"><a aria-hidden="true" tabindex="-1" href="#注释"><span class="icon icon-link"></span></a>注释</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token comment">// 这是一个注释</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Hello World!"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 这是一个注释</span>
|
||
</span><span class="code-line"><span class="token comment">/*
|
||
</span></span><span class="code-line"><span class="token comment"> 多行注释：用于注释跨多行的内容
|
||
</span></span><span class="code-line"><span class="token comment"> 上面的代码将打印出 Hello World! 到屏幕上
|
||
</span></span><span class="code-line"><span class="token comment"> 注意：多行注释不能嵌套，否则会导致编译错误
|
||
</span></span><span class="code-line"><span class="token comment">*/</span>
|
||
</span></code></pre>
|
||
<p><strong>注意</strong>:
|
||
单行注释<code>//</code>可以嵌套，<code>////////这种注释也是对的</code><br>
|
||
但行内注释应避免过长，以免影响代码可读性</p>
|
||
<p>多行注释不能嵌套，否则会导致编译错误（详见下文 <a href="#warning-%E5%92%8C-error">### Warning 和 Error</a> ）</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token comment">/* 这是一个多行注释的开始
|
||
</span></span><span class="code-line"><span class="token comment"> /* 这是嵌套的多行注释，C语言不支持 */</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="打印文本"><a aria-hidden="true" tabindex="-1" href="#打印文本"><span class="icon icon-link"></span></a>打印文本</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"I am learning C."</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> testInteger <span class="token operator">=</span> <span class="token number">5</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Number = %d"</span><span class="token punctuation">,</span> testInteger<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">float</span> f <span class="token operator">=</span> <span class="token number">5.99</span><span class="token punctuation">;</span> <span class="token comment">// 浮点数</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Value = %f"</span><span class="token punctuation">,</span> f<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">short</span> a <span class="token operator">=</span> <span class="token number">0</span>b1010110<span class="token punctuation">;</span> <span class="token comment">// 2 进制数字</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> b <span class="token operator">=</span> <span class="token number">02713</span><span class="token punctuation">;</span> <span class="token comment">// 8 进制数字</span>
|
||
</span><span class="code-line"><span class="token keyword">long</span> c <span class="token operator">=</span> <span class="token number">0X1DAB83</span><span class="token punctuation">;</span> <span class="token comment">// 16 进制数字</span>
|
||
</span><span class="code-line"><span class="token comment">//变量a和c分别为short和long型，所以输出必须加上对应的修饰符h和l</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 以 8 进制形式输出</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"a=%ho, b=%o, c=%lo\n"</span><span class="token punctuation">,</span> a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 => a=126, b=2713, c=7325603</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 以 10 进制形式输出</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"a=%hd, b=%d, c=%ld\n"</span><span class="token punctuation">,</span> a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 => a=86, b=1483, c=1944451</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 以 16 进制形式输出（字母小写）</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"a=%hx, b=%x, c=%lx\n"</span><span class="token punctuation">,</span> a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 => a=56, b=5cb, c=1dab83</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 以 16 进制形式输出（字母大写）</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"a=%hX, b=%X, c=%lX\n"</span><span class="token punctuation">,</span> a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 => a=56, b=5CB, c=1DAB83</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="控制空格数"><a aria-hidden="true" tabindex="-1" href="#控制空格数"><span class="icon icon-link"></span></a>控制空格数</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> a1<span class="token operator">=</span><span class="token number">20</span><span class="token punctuation">,</span> a2<span class="token operator">=</span><span class="token number">345</span><span class="token punctuation">,</span> a3<span class="token operator">=</span><span class="token number">700</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> b1<span class="token operator">=</span><span class="token number">56720</span><span class="token punctuation">,</span> b2<span class="token operator">=</span><span class="token number">9999</span><span class="token punctuation">,</span> b3<span class="token operator">=</span><span class="token number">20098</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> c1<span class="token operator">=</span><span class="token number">233</span><span class="token punctuation">,</span> c2<span class="token operator">=</span><span class="token number">205</span><span class="token punctuation">,</span> c3<span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> d1<span class="token operator">=</span><span class="token number">34</span><span class="token punctuation">,</span> d2<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">,</span> d3<span class="token operator">=</span><span class="token number">23</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// %-9d: 十进制输出，最少宽度为9，左对齐</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%-9d %-9d %-9d\n"</span><span class="token punctuation">,</span> a1<span class="token punctuation">,</span> a2<span class="token punctuation">,</span> a3<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%-9d %-9d %-9d\n"</span><span class="token punctuation">,</span> b1<span class="token punctuation">,</span> b2<span class="token punctuation">,</span> b3<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%-9d %-9d %-9d\n"</span><span class="token punctuation">,</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">,</span> c3<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%-9d %-9d %-9d\n"</span><span class="token punctuation">,</span> d1<span class="token punctuation">,</span> d2<span class="token punctuation">,</span> d3<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
<p>输出结果</p>
|
||
<pre class="language-bash"><code class="language-bash code-highlight"><span class="code-line"><span class="token number">20</span> <span class="token number">345</span> <span class="token number">700</span>
|
||
</span><span class="code-line"><span class="token number">56720</span> <span class="token number">9999</span> <span class="token number">20098</span>
|
||
</span><span class="code-line"><span class="token number">233</span> <span class="token number">205</span> <span class="token number">1</span>
|
||
</span><span class="code-line"><span class="token number">34</span> <span class="token number">0</span> <span class="token number">23</span>
|
||
</span></code></pre>
|
||
<p><code>%-9d</code> 中，<code>d</code> 表示以 <code>10</code> 进制输出，<code>9</code> 表示最少占 <code>9</code> 个字符的宽度，宽度不足以空格补齐，<code>-</code> 表示左对齐，如果不使用左对齐则默认右对齐</p>
|
||
<p>对于整型数据，假设：</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> a <span class="token operator">=</span> <span class="token number">12345</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span>“<span class="token operator">%</span>md”<span class="token punctuation">,</span>a<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
<ol>
|
||
<li>若 m <= 实际数据的宽度，则按实际情况输出</li>
|
||
<li>若 m > 实际数据的宽度，则在实际数据的左边用空格补齐</li>
|
||
<li><code>printf(“%0md”,a);</code> 则实际的结果不够 m 位的在数据的左边用0补齐</li>
|
||
</ol>
|
||
<p>对于浮点型数据，<strong>数据的宽度=整数部分的位数+小数点+小数部分的宽度</strong><br>
|
||
假设：</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">float</span> a <span class="token operator">=</span> <span class="token number">1.2345</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span>“<span class="token operator">%</span>m<span class="token punctuation">.</span>nf”<span class="token punctuation">,</span>a<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//m --整个数据的宽度，n--小数位数</span>
|
||
</span></code></pre>
|
||
<ol>
|
||
<li>实际小数位数>n，截去小数右边多余的小数，截去的第一位要注意四舍五入</li>
|
||
<li>实际小数位数< n，在小数的最后补0</li>
|
||
<li>若m省略则写作%.n ，整数部分按照实际输出，小数部分按照以上两个规则进行</li>
|
||
<li>m < n+1，自动突破宽度为m的限制，按照实际数据进行输出</li>
|
||
<li>m > n+1，整个数据的最左边补空格</li>
|
||
</ol>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="字符串-strings"><a aria-hidden="true" tabindex="-1" href="#字符串-strings"><span class="icon icon-link"></span></a>字符串 Strings</h3><div class="wrap-body">
|
||
<p>在C语言中，字符串是以 <code>\0</code> 结尾的字符数组，而不是一种单独的数据类型<br>
|
||
可以通过字符数组来表示字符串</p>
|
||
<p>定义并打印字符串</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">char</span> greetings<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token string">"Hello World!"</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%s"</span><span class="token punctuation">,</span> greetings<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
<p>访问字符串中的字符</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">char</span> greetings<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token string">"Hello World!"</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%c"</span><span class="token punctuation">,</span> greetings<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">//这里我们访问字符串 greetings 的第一个字符'H'</span>
|
||
</span></code></pre>
|
||
<p>修改字符串中的字符</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">char</span> greetings<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token string">"Hello World!"</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">greetings<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token char">'J'</span><span class="token punctuation">;</span> <span class="token comment">//// 修改第一个字符为 'J'</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%s"</span><span class="token punctuation">,</span> greetings<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 "Jello World!"</span>
|
||
</span></code></pre>
|
||
<p>另一种创建字符串的方法</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">char</span> greetings<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token char">'H'</span><span class="token punctuation">,</span><span class="token char">'e'</span><span class="token punctuation">,</span><span class="token char">'l'</span><span class="token punctuation">,</span><span class="token char">'l'</span><span class="token punctuation">,</span><span class="token char">'\0'</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%s"</span><span class="token punctuation">,</span> greetings<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 "Hell!"</span>
|
||
</span></code></pre>
|
||
<p>C语言中<strong>没有</strong><code>String</code>类型，字符串是由字符数组(Array)<code>char[]</code>来表示的，且必须以 \0 结尾以标识字符串的结束</p>
|
||
</div></div></div><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="条件判断"><a aria-hidden="true" tabindex="-1" href="#条件判断"><span class="icon icon-link"></span></a>条件判断</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> time <span class="token operator">=</span> <span class="token number">20</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span>time <span class="token operator"><</span> <span class="token number">18</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"再会！"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"晚上好！"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 -> "晚上好！"</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> time <span class="token operator">=</span> <span class="token number">22</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span>time <span class="token operator"><</span> <span class="token number">10</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"早上好！"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token keyword">if</span> <span class="token punctuation">(</span>time <span class="token operator"><</span> <span class="token number">20</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"再会！"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"晚上好！"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 -> "晚上好！"</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> time <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span>time <span class="token operator">></span> <span class="token number">8</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token comment">//再嵌套一个if</span>
|
||
</span><span class="code-line"> <span class="token keyword">if</span> <span class="token punctuation">(</span>time <span class="token operator"><</span> <span class="token number">12</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"中午好！"</span><span class="token punctuation">)</span>
|
||
</span><span class="code-line"> <span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 -> "中午好！"</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="三元运算符"><a aria-hidden="true" tabindex="-1" href="#三元运算符"><span class="icon icon-link"></span></a>三元运算符</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
<p>三元运算符（? :）是一种简洁的条件判断方式，常用于根据条件选择表达式的值,由三个部分组成：</p>
|
||
<ul>
|
||
<li>一个条件表达式</li>
|
||
<li>条件为真时的结果</li>
|
||
<li>条件为假时的结果<br>
|
||
基本语法：<code>(condition) ? expression1 : expression2;</code><br>
|
||
如果<code>condition</code>为真，则返回<code>expression1</code>否则返回<code>expression2</code>。</li>
|
||
</ul>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> time <span class="token operator">=</span> <span class="token number">20</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">(</span>time <span class="token operator"><</span> <span class="token number">18</span><span class="token punctuation">)</span> <span class="token operator">?</span> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"再会！"</span><span class="token punctuation">)</span> <span class="token operator">:</span> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"晚上好！"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 -> "晚上好！"</span>
|
||
</span></code></pre>
|
||
<p>三元运算符可以嵌套使用，但嵌套层级太多会导致代码可读性下降，不建议在实际场景使用</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> time <span class="token operator">=</span> <span class="token number">22</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token punctuation">(</span>time <span class="token operator"><</span> <span class="token number">10</span><span class="token punctuation">)</span> <span class="token operator">?</span> <span class="token string">"早上好！"</span> <span class="token operator">:</span> <span class="token punctuation">(</span>time <span class="token operator"><</span> <span class="token number">20</span><span class="token punctuation">)</span> <span class="token operator">?</span> <span class="token string">"再会！"</span> <span class="token operator">:</span> <span class="token string">"晚上好！"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 -> "晚上好！"</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="switch"><a aria-hidden="true" tabindex="-1" href="#switch"><span class="icon icon-link"></span></a>Switch</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> day <span class="token operator">=</span> <span class="token number">4</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">switch</span> <span class="token punctuation">(</span>day<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">case</span> <span class="token number">3</span><span class="token operator">:</span> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"周三"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">break</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">case</span> <span class="token number">4</span><span class="token operator">:</span> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"周四"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">break</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">default</span><span class="token operator">:</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"期待周末"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 -> "周四" (day 4)</span>
|
||
</span><span class="code-line"><span class="token comment">/* 解释：
|
||
</span></span><span class="code-line"><span class="token comment">switch 语句会根据表达式 day 的值来跳转到匹配的 case 标签
|
||
</span></span><span class="code-line"><span class="token comment">匹配到 case 4 时，会执行相应的代码并通过 break 跳出 switch 语句
|
||
</span></span><span class="code-line"><span class="token comment">如果没有匹配到任何 case，则会执行 default 语句（如果存在）
|
||
</span></span><span class="code-line"><span class="token comment">*/</span>
|
||
</span></code></pre>
|
||
<p>注意：</p>
|
||
<ol>
|
||
<li>switch 后面括号中的表达式可以是整型、字符型和枚举型</li>
|
||
<li>在<code>case</code>后的各常量表达式的值不能相同</li>
|
||
<li>在<code>case</code>后，允许有多个语句，可以不用{ }括起来，而整个 switc h结构一定要有一对{}</li>
|
||
<li>各<code>case</code>和<code>default</code>语句的先后顺序可以改变，不影响程序执行结果</li>
|
||
<li><code>break</code>语句用于结束 switch，如果没有<code>break</code>，程序会穿透到下一个<code>case</code>继续执行，例如</li>
|
||
</ol>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> day <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">switch</span> <span class="token punctuation">(</span>day<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">case</span> <span class="token number">3</span><span class="token operator">:</span> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"周三"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">case</span> <span class="token number">4</span><span class="token operator">:</span> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"周四"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">break</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">default</span><span class="token operator">:</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"期待周末"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 -> "周三周四" </span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="while-循环"><a aria-hidden="true" tabindex="-1" href="#while-循环"><span class="icon icon-link"></span></a>While 循环</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">while</span> <span class="token punctuation">(</span>i <span class="token operator"><</span> <span class="token number">5</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d\n"</span><span class="token punctuation">,</span> i<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> i<span class="token operator">++</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">/*解释：
|
||
</span></span><span class="code-line"><span class="token comment">在 while 循环中，首先检查条件 i < 5 是否为真
|
||
</span></span><span class="code-line"><span class="token comment">如果为真，程序进入循环体，执行打印操作并增加 i 的值
|
||
</span></span><span class="code-line"><span class="token comment">循环会继续进行，直到 i 达到 5，此时条件 i < 5 不再为真，循环结束
|
||
</span></span><span class="code-line"><span class="token comment">*/</span>
|
||
</span></code></pre>
|
||
<p><strong>注意</strong>：不要忘记在循环体内修改循环条件中的变量（如 i++），否则循环将永远执行下去，成为“死循环”</p>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="dowhile-循环"><a aria-hidden="true" tabindex="-1" href="#dowhile-循环"><span class="icon icon-link"></span></a>Do/While 循环</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">do</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d\n"</span><span class="token punctuation">,</span> i<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> i<span class="token operator">++</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span> <span class="token keyword">while</span> <span class="token punctuation">(</span>i <span class="token operator"><</span> <span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">/*解释：
|
||
</span></span><span class="code-line"><span class="token comment">在 do/while 循环中，循环体至少执行一次，因为条件检查是在循环体执行之后进行的
|
||
</span></span><span class="code-line"><span class="token comment">首先执行 do 中的代码，然后检查条件 i < 5 是否为真
|
||
</span></span><span class="code-line"><span class="token comment">如果为真，继续执行循环；如果为假，则退出循环
|
||
</span></span><span class="code-line"><span class="token comment">/*
|
||
</span></span></code></pre>
|
||
<p><strong>注意</strong>：与<code>while</code>循环不同，<code>do/while</code>循环会确保至少执行一次循环体，即使条件一开始就为假<br>
|
||
例如，以下代码虽然条件<code>i < 5</code>初始时为假，但仍然会执行一次：</p>
|
||
<pre class="language-c"><code class="language-C code-highlight"><span class="code-line"><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">5</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">do</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d\n"</span><span class="token punctuation">,</span> i<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 输出 5</span>
|
||
</span><span class="code-line"> i<span class="token operator">++</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span> <span class="token keyword">while</span> <span class="token punctuation">(</span>i <span class="token operator"><</span> <span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="for-循环"><a aria-hidden="true" tabindex="-1" href="#for-循环"><span class="icon icon-link"></span></a>For 循环</h3><div class="wrap-body">
|
||
<p>语法：</p>
|
||
<pre class="language-c"><code class="language-C code-highlight"><span class="code-line"><span class="token keyword">for</span><span class="token punctuation">(</span>表达式 <span class="token number">1</span><span class="token punctuation">;</span>表达式 <span class="token number">2</span><span class="token punctuation">;</span>表达式 <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
|
||
</span><span class="code-line"> 循环体语句<span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
<p>表达式 1：设置初始条件，只执行一次，为 0 个或多个变量设置初值<br>
|
||
表达式 2：是循环条件表达式，用来判定是否继续循环。在每次执行循环体之前要先执行表达式 2，然后再决定是否继续执行循环<br>
|
||
表达式 3：作为循环的调整，比如是循环体变量增值，它是执行循环体语句之后再执行</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> i<span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">for</span> <span class="token punctuation">(</span>i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator"><</span> <span class="token number">5</span><span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d\n"</span><span class="token punctuation">,</span> i<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">/* 输出：
|
||
</span></span><span class="code-line"><span class="token comment">0
|
||
</span></span><span class="code-line"><span class="token comment">1
|
||
</span></span><span class="code-line"><span class="token comment">2
|
||
</span></span><span class="code-line"><span class="token comment">3
|
||
</span></span><span class="code-line"><span class="token comment">4
|
||
</span></span><span class="code-line"><span class="token comment">*/</span>
|
||
</span></code></pre>
|
||
<p><strong>注意</strong>：</p>
|
||
<ol>
|
||
<li>for 语句的三个表达式不是必须的</li>
|
||
<li>当条件表达式(表达式 2)的值为假(为 0)时 for 循环语句就结束</li>
|
||
<li>可以在循环体内执行<code>break</code>,<code>continue</code>,<code>goto</code>语句</li>
|
||
<li>若表达式 2 是空的，表明表达式 2 的值一直是真，即死循环<br>
|
||
如：<code>for(;;) //死循环语句 相当于while(1)</code></li>
|
||
</ol>
|
||
<p><strong>变体</strong>：</p>
|
||
<ul>
|
||
<li><code>for(i = m; i < n; i++)</code>会从 i = m 开始到 i = n-1，循环 n - m 次</li>
|
||
<li><code>for(i = m; i <= n; i++)</code>会从 i = m 到 i = n，循环 n - m + 1 次</li>
|
||
</ul>
|
||
</div></div></div><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="跳出循环中断语句-breakcontinuegoto"><a aria-hidden="true" tabindex="-1" href="#跳出循环中断语句-breakcontinuegoto"><span class="icon icon-link"></span></a>跳出循环(中断语句) Break/Continue/Goto</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
<p><code>break</code>语句：跳出本层循环，执行循环后的语句<br>
|
||
<code>continue</code>语句：跳出本次循环，执行下一次循环<br>
|
||
<code>goto</code>语句：跳出到指定的标号位</p>
|
||
<p><strong>1.<code>break</code>语句</strong>:</p>
|
||
<p><code>break</code>用于跳出当前的循环或<code>switch</code>语句，直接跳到循环或<code>switch</code>语句之后的下一条语句<br>
|
||
通常用于在特定条件下提前结束循环</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> i<span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">for</span> <span class="token punctuation">(</span>i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator"><</span> <span class="token number">10</span><span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">if</span> <span class="token punctuation">(</span>i <span class="token operator">==</span> <span class="token number">4</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">break</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token punctuation">}</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d\n"</span><span class="token punctuation">,</span> i<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">//输出：</span>
|
||
</span><span class="code-line"><span class="token comment">//0 1 2 3 4(换行符使用空格代替)</span>
|
||
</span></code></pre>
|
||
<p>当<code>i</code>等于 4 时，<code>break</code>语句使得循环提前结束，因此没有打印出 4 及之后的值</p>
|
||
<p><strong>2.<code>continue</code>语句</strong>:</p>
|
||
<p><code>continue</code>用于跳过当前循环中的剩余语句(在for循环中相当于直接执行表达式3)，直接进入下一次循环的条件判断阶段<br>
|
||
通常用于跳过某些特定的循环迭代</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> i<span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">for</span> <span class="token punctuation">(</span>i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator"><</span> <span class="token number">10</span><span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">if</span> <span class="token punctuation">(</span>i <span class="token operator">==</span> <span class="token number">4</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">continue</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token punctuation">}</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d\n"</span><span class="token punctuation">,</span> i<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">//输出：</span>
|
||
</span><span class="code-line"><span class="token comment">//0 1 2 3 5 6 7 8 9(换行符使用空格代替)</span>
|
||
</span></code></pre>
|
||
<p>当<code>i</code>等于 4 时，<code>continue</code>会跳过打印语句，因此 4 被跳过，不会输出</p>
|
||
<p><strong>3.<code>goto</code>语句</strong>:</p>
|
||
<p><code>goto</code>用于无条件跳转到程序中的指定标签位置</p>
|
||
<pre class="language-c"><code class="language-C code-highlight"><span class="code-line"><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">while</span> <span class="token punctuation">(</span>i <span class="token operator"><</span> <span class="token number">10</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">if</span> <span class="token punctuation">(</span>i <span class="token operator">==</span> <span class="token number">4</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">goto</span> skip<span class="token punctuation">;</span> <span class="token comment">// 跳转到 skip 标签</span>
|
||
</span><span class="code-line"> <span class="token punctuation">}</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d\n"</span><span class="token punctuation">,</span> i<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> i<span class="token operator">++</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line">skip<span class="token operator">:</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Exited the loop at i = %d\n"</span><span class="token punctuation">,</span> i<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">/* 输出：
|
||
</span></span><span class="code-line"><span class="token comment">0
|
||
</span></span><span class="code-line"><span class="token comment">1
|
||
</span></span><span class="code-line"><span class="token comment">2
|
||
</span></span><span class="code-line"><span class="token comment">3
|
||
</span></span><span class="code-line"><span class="token comment">Exited the loop at i = 4
|
||
</span></span><span class="code-line"><span class="token comment">*/</span>
|
||
</span></code></pre>
|
||
<p><code>goto skip</code>语句将程序的控制流跳转到标签<code>skip</code>处，导致循环在<code>i = 4</code>时直接结束，并输出<code>Exited the loop at i = 4</code></p>
|
||
<p><strong>注意</strong>:</p>
|
||
<ol>
|
||
<li><code>label标签</code>必须是在当前函数内定义的标签。标签的命名规则与变量的命名规则相同，但标签不能与C语言的关键字冲突</li>
|
||
<li><code>goto</code>语句通常用于跳转到同一函数内的某个位置，但也可以跳转到同一文件中的其他函数内的标签（不推荐）</li>
|
||
<li>goto语句应慎用，因为过多或滥用goto语句可能会导致代码逻辑混乱、难以维护和阅读。通常情况下，可以使用循环或条件语句等结构化的控制流语句来代替goto语句</li>
|
||
</ol>
|
||
</div></div></div><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="数组-arrays"><a aria-hidden="true" tabindex="-1" href="#数组-arrays"><span class="icon icon-link"></span></a>数组 Arrays</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> myNumbers<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">25</span><span class="token punctuation">,</span> <span class="token number">50</span><span class="token punctuation">,</span> <span class="token number">75</span><span class="token punctuation">,</span> <span class="token number">100</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d"</span><span class="token punctuation">,</span> myNumbers<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 25</span>
|
||
</span></code></pre>
|
||
<p>更改数组元素</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> myNumbers<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">25</span><span class="token punctuation">,</span> <span class="token number">50</span><span class="token punctuation">,</span> <span class="token number">75</span><span class="token punctuation">,</span> <span class="token number">100</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">myNumbers<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">33</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d"</span><span class="token punctuation">,</span> myNumbers<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
<p>循环遍历数组</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> myNumbers<span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">25</span><span class="token punctuation">,</span> <span class="token number">50</span><span class="token punctuation">,</span> <span class="token number">75</span><span class="token punctuation">,</span> <span class="token number">100</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> i<span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">for</span> <span class="token punctuation">(</span>i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator"><</span> <span class="token number">4</span><span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d\n"</span><span class="token punctuation">,</span> myNumbers<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
<p>设置数组大小</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token comment">// 声明一个由四个整数组成的数组：</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> myNumbers<span class="token punctuation">[</span><span class="token number">4</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 添加元素</span>
|
||
</span><span class="code-line">myNumbers<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">25</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">myNumbers<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">50</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">myNumbers<span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">75</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">myNumbers<span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token number">100</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="枚举-enum"><a aria-hidden="true" tabindex="-1" href="#枚举-enum"><span class="icon icon-link"></span></a>枚举 Enum</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">enum</span> <span class="token class-name">week</span> <span class="token punctuation">{</span> Mon <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span> Tues<span class="token punctuation">,</span> Wed<span class="token punctuation">,</span> Thurs<span class="token punctuation">,</span> Fri<span class="token punctuation">,</span> Sat<span class="token punctuation">,</span> Sun <span class="token punctuation">}</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
<p>定义枚举变量</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">enum</span> <span class="token class-name">week</span> a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c<span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">enum</span> <span class="token class-name">week</span> <span class="token punctuation">{</span> Mon <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span> Tues<span class="token punctuation">,</span> Wed<span class="token punctuation">,</span> Thurs<span class="token punctuation">,</span> Fri<span class="token punctuation">,</span> Sat<span class="token punctuation">,</span> Sun <span class="token punctuation">}</span> a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c<span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
<p>有了枚举变量，就可以把列表中的值赋给它</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">enum</span> <span class="token class-name">week</span> <span class="token punctuation">{</span> Mon <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span> Tues<span class="token punctuation">,</span> Wed<span class="token punctuation">,</span> Thurs<span class="token punctuation">,</span> Fri<span class="token punctuation">,</span> Sat<span class="token punctuation">,</span> Sun <span class="token punctuation">}</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">enum</span> <span class="token class-name">week</span> a <span class="token operator">=</span> Mon<span class="token punctuation">,</span> b <span class="token operator">=</span> Wed<span class="token punctuation">,</span> c <span class="token operator">=</span> Sat<span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 或者</span>
|
||
</span><span class="code-line"><span class="token keyword">enum</span> <span class="token class-name">week</span><span class="token punctuation">{</span> Mon <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span> Tues<span class="token punctuation">,</span> Wed<span class="token punctuation">,</span> Thurs<span class="token punctuation">,</span> Fri<span class="token punctuation">,</span> Sat<span class="token punctuation">,</span> Sun <span class="token punctuation">}</span> a <span class="token operator">=</span> Mon<span class="token punctuation">,</span> b <span class="token operator">=</span> Wed<span class="token punctuation">,</span> c <span class="token operator">=</span> Sat<span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="枚举示例应用"><a aria-hidden="true" tabindex="-1" href="#枚举示例应用"><span class="icon icon-link"></span></a>枚举示例应用</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">enum</span> <span class="token class-name">week</span> <span class="token punctuation">{</span>Mon <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span> Tues<span class="token punctuation">,</span> Wed<span class="token punctuation">,</span> Thurs<span class="token punctuation">}</span> day<span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token function">scanf</span><span class="token punctuation">(</span><span class="token string">"%d"</span><span class="token punctuation">,</span> <span class="token operator">&</span>day<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">switch</span><span class="token punctuation">(</span>day<span class="token punctuation">)</span><span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">case</span> Mon<span class="token operator">:</span> <span class="token function">puts</span><span class="token punctuation">(</span><span class="token string">"Monday"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">break</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">case</span> Tues<span class="token operator">:</span> <span class="token function">puts</span><span class="token punctuation">(</span><span class="token string">"Tuesday"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">break</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">case</span> Wed<span class="token operator">:</span> <span class="token function">puts</span><span class="token punctuation">(</span><span class="token string">"Wednesday"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">break</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">case</span> Thurs<span class="token operator">:</span> <span class="token function">puts</span><span class="token punctuation">(</span><span class="token string">"Thursday"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">break</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">default</span><span class="token operator">:</span> <span class="token function">puts</span><span class="token punctuation">(</span><span class="token string">"Error!"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="用户输入"><a aria-hidden="true" tabindex="-1" href="#用户输入"><span class="icon icon-link"></span></a>用户输入</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token comment">// 创建一个整数变量来存储我们从用户那里得到的数字</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> myNum<span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 要求用户输入一个数字</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"请输入一个数字: \n"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 获取并保存用户输入的号码</span>
|
||
</span><span class="code-line"><span class="token function">scanf</span><span class="token punctuation">(</span><span class="token string">"%d"</span><span class="token punctuation">,</span> <span class="token operator">&</span>myNum<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 输出用户输入的数字</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"您输入的数字: %d"</span><span class="token punctuation">,</span> myNum<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="用户输入字符串"><a aria-hidden="true" tabindex="-1" href="#用户输入字符串"><span class="icon icon-link"></span></a>用户输入字符串</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token comment">// 创建一个字符串</span>
|
||
</span><span class="code-line"><span class="token keyword">char</span> firstName<span class="token punctuation">[</span><span class="token number">30</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 要求用户输入一些文本</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"输入您的名字: \n"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 获取并保存文本</span>
|
||
</span><span class="code-line"><span class="token function">scanf</span><span class="token punctuation">(</span><span class="token string">"%s"</span><span class="token punctuation">,</span> firstName<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出文本</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Hello %s."</span><span class="token punctuation">,</span> firstName<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="内存地址"><a aria-hidden="true" tabindex="-1" href="#内存地址"><span class="icon icon-link"></span></a>内存地址</h3><div class="wrap-body">
|
||
<p>创建变量时，会为该变量分配一个内存地址</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> myAge <span class="token operator">=</span> <span class="token number">43</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%p"</span><span class="token punctuation">,</span> <span class="token operator">&</span>myAge<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出：0x7ffe5367e044</span>
|
||
</span></code></pre>
|
||
<p>要访问它，请使用引用运算符 (<code>&</code>)</p>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="创建指针"><a aria-hidden="true" tabindex="-1" href="#创建指针"><span class="icon icon-link"></span></a>创建指针</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> myAge <span class="token operator">=</span> <span class="token number">43</span><span class="token punctuation">;</span> <span class="token comment">// 一个 int 变量</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d"</span><span class="token punctuation">,</span> myAge<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 输出 myAge(43)的值</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 输出 myAge 的内存地址（0x7ffe5367e044）</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%p"</span><span class="token punctuation">,</span> <span class="token operator">&</span>myAge<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="指针变量"><a aria-hidden="true" tabindex="-1" href="#指针变量"><span class="icon icon-link"></span></a>指针变量</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> myAge <span class="token operator">=</span> <span class="token number">43</span><span class="token punctuation">;</span> <span class="token comment">// 一个 int 变量</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span><span class="token operator">*</span> ptr <span class="token operator">=</span> <span class="token operator">&</span>myAge<span class="token punctuation">;</span> <span class="token comment">// 名为 ptr 的指针变量，用于存储 myAge 的地址</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d\n"</span><span class="token punctuation">,</span> myAge<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 输出 myAge (43) 的值</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%p\n"</span><span class="token punctuation">,</span> <span class="token operator">&</span>myAge<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 输出 myAge 的内存地址（0x7ffe5367e044）</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%p\n"</span><span class="token punctuation">,</span> ptr<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 用指针（0x7ffe5367e044）输出myAge的内存地址</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="取消引用"><a aria-hidden="true" tabindex="-1" href="#取消引用"><span class="icon icon-link"></span></a>取消引用</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> myAge <span class="token operator">=</span> <span class="token number">43</span><span class="token punctuation">;</span> <span class="token comment">// 变量声明</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span><span class="token operator">*</span> ptr <span class="token operator">=</span> <span class="token operator">&</span>myAge<span class="token punctuation">;</span> <span class="token comment">// 指针声明</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 参考：用指针输出 myAge 的</span>
|
||
</span><span class="code-line"><span class="token comment">// 内存地址（0x7ffe5367e044）</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%p\n"</span><span class="token punctuation">,</span> ptr<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 取消引用：用指针输出 myAge 的值 (43)</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d\n"</span><span class="token punctuation">,</span> <span class="token operator">*</span>ptr<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="运算符"><a aria-hidden="true" tabindex="-1" href="#运算符"><span class="icon icon-link"></span></a>运算符</h2><div class="wrap-body">
|
||
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="算术运算符"><a aria-hidden="true" tabindex="-1" href="#算术运算符"><span class="icon icon-link"></span></a>算术运算符</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> myNum <span class="token operator">=</span> <span class="token number">100</span> <span class="token operator">+</span> <span class="token number">50</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> sum1 <span class="token operator">=</span> <span class="token number">100</span> <span class="token operator">+</span> <span class="token number">50</span><span class="token punctuation">;</span> <span class="token comment">// 150 (100 + 50)</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> sum2 <span class="token operator">=</span> sum1 <span class="token operator">+</span> <span class="token number">250</span><span class="token punctuation">;</span> <span class="token comment">// 400 (150 + 250)</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> sum3 <span class="token operator">=</span> sum2 <span class="token operator">+</span> sum2<span class="token punctuation">;</span> <span class="token comment">// 800 (400 + 400)</span>
|
||
</span></code></pre>
|
||
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|
||
<table><thead><tr><th>Operator</th><th>Name</th><th>Description</th><th>Example</th></tr></thead><tbody><tr><td><code>+</code></td><td>加</td><td>将两个值相加</td><td><code>x + y</code></td></tr><tr><td><code>-</code></td><td>减</td><td>从另一个值中减去一个值</td><td><code>x - y</code></td></tr><tr><td><code>*</code></td><td>乘</td><td>将两个值相乘</td><td><code>x * y</code></td></tr><tr><td><code>/</code></td><td>除</td><td>将一个值除以另一个</td><td><code>x / y</code></td></tr><tr><td><code>%</code></td><td>取模</td><td>返回除法余数</td><td><code>x % y</code></td></tr><tr><td><code>++</code></td><td>增量</td><td>将变量的值增加 1</td><td><code>++</code></td></tr><tr><td><code>--</code></td><td>乘量</td><td>将变量的值减 1</td><td><code>--x</code></td></tr></tbody></table>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="赋值运算符"><a aria-hidden="true" tabindex="-1" href="#赋值运算符"><span class="icon icon-link"></span></a>赋值运算符</h3><div class="wrap-body">
|
||
|
||
|
||
|
||
|
||
|
||
|
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|
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|
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|
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<table><thead><tr><th>符号</th><th>示例</th><th>如同</th></tr></thead><tbody><tr><td><code>=</code></td><td>x <code>=</code> 5</td><td>x <code>=</code> 5</td></tr><tr><td><code>+=</code></td><td>x <code>+=</code> 3</td><td>x <code>=</code> x <code>+</code> 3</td></tr><tr><td><code>-=</code></td><td>x <code>-=</code> 3</td><td>x <code>=</code> x <code>-</code> 3</td></tr><tr><td><code>*=</code></td><td>x <code>*=</code> 3</td><td>x <code>=</code> x <code>*</code> 3</td></tr><tr><td><code>/=</code></td><td>x <code>/=</code> 3</td><td>x <code>=</code> x <code>/</code> 3</td></tr><tr><td><code>%=</code></td><td>x <code>%=</code> 3</td><td>x <code>=</code> x <code>%</code> 3</td></tr><tr><td><code>&=</code></td><td>x <code>&=</code> 3</td><td>x <code>=</code> x <code>&</code> 3</td></tr><tr><td><code>|=</code></td><td>x <code>|=</code> 3</td><td>x <code>=</code> x <code>|</code> 3</td></tr><tr><td><code>^=</code></td><td>x <code>^=</code> 3</td><td>x <code>=</code> x <code>^</code> 3</td></tr><tr><td><code>>>=</code></td><td>x <code>>>=</code> 3</td><td>x <code>=</code> x <code>>></code> 3</td></tr><tr><td><code><<=</code></td><td>x <code><<=</code> 3</td><td>x <code>=</code> x <code><<</code> 3</td></tr></tbody></table>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="比较运算符"><a aria-hidden="true" tabindex="-1" href="#比较运算符"><span class="icon icon-link"></span></a>比较运算符</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> x <span class="token operator">=</span> <span class="token number">5</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> y <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d"</span><span class="token punctuation">,</span> x <span class="token operator">></span> y<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 返回 1（真），因为 5 大于 3</span>
|
||
</span></code></pre>
|
||
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<table><thead><tr><th>符号</th><th>名称</th><th>示例</th></tr></thead><tbody><tr><td><code>==</code></td><td>等于</td><td>x <code>==</code> y</td></tr><tr><td><code>!=</code></td><td>不等于</td><td>x <code>!=</code> y</td></tr><tr><td><code>></code></td><td>大于</td><td>x <code>></code> y</td></tr><tr><td><code><</code></td><td>小于</td><td>x <code><</code> y</td></tr><tr><td><code>>=</code></td><td>大于或等于</td><td>x <code>>=</code> y</td></tr><tr><td><code><=</code></td><td>小于或等于</td><td>x <code><=</code> y</td></tr></tbody></table>
|
||
<p>比较运算符用于比较两个值</p>
|
||
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="逻辑运算符"><a aria-hidden="true" tabindex="-1" href="#逻辑运算符"><span class="icon icon-link"></span></a>逻辑运算符</h3><div class="wrap-body">
|
||
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<table><thead><tr><th>符号</th><th>名称</th><th>说明</th><th>示例</th></tr></thead><tbody><tr><td><code>&&</code></td><td><code>与</code>逻辑</td><td>如果两个语句都为真，则返回真</td><td><code>x < 5 && x < 10</code></td></tr><tr><td><code>||</code></td><td><code>或</code>逻辑</td><td>如果其中一个语句为真，则返回真</td><td><code>x < 5 || x < 4</code></td></tr><tr><td><code>!</code></td><td><code>非</code>逻辑</td><td>反转结果，如果结果为真则返回假</td><td><code>!(x < 5 && x < 10)</code></td></tr></tbody></table>
|
||
</div></div></div><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="运算符示例"><a aria-hidden="true" tabindex="-1" href="#运算符示例"><span class="icon icon-link"></span></a>运算符示例</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">unsigned</span> <span class="token keyword">int</span> a <span class="token operator">=</span> <span class="token number">60</span><span class="token punctuation">;</span> <span class="token comment">/* 60 = 0011 1100 */</span>
|
||
</span><span class="code-line"><span class="token keyword">unsigned</span> <span class="token keyword">int</span> b <span class="token operator">=</span> <span class="token number">13</span><span class="token punctuation">;</span> <span class="token comment">/* 13 = 0000 1101 */</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> c <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line">c <span class="token operator">=</span> a <span class="token operator">&</span> b<span class="token punctuation">;</span> <span class="token comment">/* 12 = 0000 1100 */</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Line 1 - c 的值是 %d\n"</span><span class="token punctuation">,</span> c <span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line">c <span class="token operator">=</span> a <span class="token operator">|</span> b<span class="token punctuation">;</span> <span class="token comment">/* 61 = 0011 1101 */</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Line 2 - c 的值是 %d\n"</span><span class="token punctuation">,</span> c <span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">c <span class="token operator">=</span> a <span class="token operator">^</span> b<span class="token punctuation">;</span> <span class="token comment">/* 49 = 0011 0001 */</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Line 3 - c 的值是 %d\n"</span><span class="token punctuation">,</span> c <span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">c <span class="token operator">=</span> <span class="token operator">~</span>a<span class="token punctuation">;</span> <span class="token comment">/*-61 = 1100 0011 */</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Line 4 - c 的值是 %d\n"</span><span class="token punctuation">,</span> c <span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">c <span class="token operator">=</span> a <span class="token operator"><<</span> <span class="token number">2</span><span class="token punctuation">;</span> <span class="token comment">/* 240 = 1111 0000 */</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Line 5 - c 的值是 %d\n"</span><span class="token punctuation">,</span> c <span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">c <span class="token operator">=</span> a <span class="token operator">>></span> <span class="token number">2</span><span class="token punctuation">;</span> <span class="token comment">/* 15 = 0000 1111 */</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Line 6 - c 的值是 %d\n"</span><span class="token punctuation">,</span> c <span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="位运算符"><a aria-hidden="true" tabindex="-1" href="#位运算符"><span class="icon icon-link"></span></a>位运算符</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=col-span-2-->
|
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|
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<table><thead><tr><th align="left">运算符</th><th align="left">描述</th><th align="left">实例</th></tr></thead><tbody><tr><td align="left"><code>&</code></td><td align="left">按位与操作，按二进制位进行"与"运算</td><td align="left"><code>(A & B)</code> 将得到 <code>12</code> 即为 0000 1100</td></tr><tr><td align="left"><code>|</code></td><td align="left">按位或运算符，按二进制位进行"或"运算</td><td align="left"><code>(A | B)</code> 将得到 <code>61</code> 即为 0011 1101</td></tr><tr><td align="left"><code>^</code></td><td align="left">异或运算符，按二进制位进行"异或"运算</td><td align="left"><code>(A ^ B)</code> 将得到 <code>49</code> 即为 0011 0001</td></tr><tr><td align="left"><code>~</code></td><td align="left">取反运算符，按二进制位进行"取反"运算</td><td align="left"><code>(~A)</code> 将得到 <code>-61</code> 即为 1100 0011</td></tr><tr><td align="left"><code><<</code></td><td align="left">二进制左移运算符</td><td align="left"><code>A << 2</code> 将得到 <code>240</code> 即为 1111 0000</td></tr><tr><td align="left"><code>>></code></td><td align="left">二进制右移运算符</td><td align="left"><code>A >> 2</code> 将得到 <code>15</code> 即为 0000 1111</td></tr></tbody></table>
|
||
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="数据类型-data-types"><a aria-hidden="true" tabindex="-1" href="#数据类型-data-types"><span class="icon icon-link"></span></a>数据类型 Data Types</h2><div class="wrap-body">
|
||
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="基本数据类型"><a aria-hidden="true" tabindex="-1" href="#基本数据类型"><span class="icon icon-link"></span></a>基本数据类型</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=col-span-2-->
|
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|
||
<table><thead><tr><th>数据类型</th><th>大小 Size</th><th>范围 Range</th><th>描述 Description</th></tr></thead><tbody><tr><td><code>char</code></td><td>1 字节</td><td><code>−128</code> ~ <code>127</code></td><td>单个字符/字母/数字/ASCII</td></tr><tr><td><code>signed char</code></td><td>1 字节</td><td><code>−128</code> ~ <code>127</code></td><td>-</td></tr><tr><td><code>unsigned char</code></td><td>1 字节</td><td><code>0</code> ~ <code>255</code></td><td>-</td></tr><tr><td><code>int</code></td><td><code>2</code> 到 <code>4</code> 字节</td><td><code>−32,768</code> ~ <code>32,767</code></td><td>存储整数</td></tr><tr><td><code>signed int</code></td><td>2 字节</td><td><code>−32,768</code> ~ <code>32,767</code></td><td></td></tr><tr><td><code>unsigned int</code></td><td>2 字节</td><td><code>0</code> ~ <code>65,535</code></td><td></td></tr><tr><td><code>short int</code></td><td>2 字节</td><td><code>−32,768</code> ~ <code>32,767</code></td><td></td></tr><tr><td><code>signed short int</code></td><td>2 字节</td><td><code>−32,768</code> ~ <code>32,767</code></td><td></td></tr><tr><td><code>unsigned short int</code></td><td>2 字节</td><td><code>0</code> ~ <code>65,535</code></td><td></td></tr><tr><td><code>long int</code></td><td>4 字节</td><td><code>-2,147,483,648</code> ~ <code>2,147,483,647</code></td><td></td></tr><tr><td><code>signed long int</code></td><td>4 字节</td><td><code>-2,147,483,648</code> ~ <code>2,147,483,647</code></td><td></td></tr><tr><td><code>unsigned long int</code></td><td>4 字节</td><td><code>0</code> ~ <code>4,294,967,295</code></td><td></td></tr><tr><td><code>float</code></td><td>4 字节</td><td></td><td></td></tr><tr><td><code>double</code></td><td>8 字节</td><td></td><td></td></tr><tr><td><code>long double</code></td><td>10 字节</td><td></td><td></td></tr></tbody></table>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="数据类型"><a aria-hidden="true" tabindex="-1" href="#数据类型"><span class="icon icon-link"></span></a>数据类型</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token comment">// 创建变量</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> myNum <span class="token operator">=</span> <span class="token number">5</span><span class="token punctuation">;</span> <span class="token comment">// 整数</span>
|
||
</span><span class="code-line"><span class="token keyword">float</span> myFloatNum <span class="token operator">=</span> <span class="token number">5.99</span><span class="token punctuation">;</span> <span class="token comment">// 浮点数</span>
|
||
</span><span class="code-line"><span class="token keyword">char</span> myLetter <span class="token operator">=</span> <span class="token char">'D'</span><span class="token punctuation">;</span> <span class="token comment">// 字符串</span>
|
||
</span><span class="code-line"><span class="token comment">// 高精度浮点数据或数字</span>
|
||
</span><span class="code-line"><span class="token keyword">double</span> myDouble <span class="token operator">=</span> <span class="token number">3.2325467</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 打印输出变量</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d\n"</span><span class="token punctuation">,</span> myNum<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%f\n"</span><span class="token punctuation">,</span> myFloatNum<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%c\n"</span><span class="token punctuation">,</span> myLetter<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%lf\n"</span><span class="token punctuation">,</span> myDouble<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
<hr>
|
||
|
||
|
||
|
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|
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|
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|
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|
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|
||
<table><thead><tr><th align="left">数据类型</th><th align="left">说 明</th></tr></thead><tbody><tr><td align="left"><code>char</code></td><td align="left">字符型</td></tr><tr><td align="left"><code>short</code></td><td align="left">短整型</td></tr><tr><td align="left"><code>int</code></td><td align="left">整型</td></tr><tr><td align="left"><code>long</code></td><td align="left">长整型</td></tr><tr><td align="left"><code>float</code></td><td align="left">单精度浮点型</td></tr><tr><td align="left"><code>double</code></td><td align="left">双精度浮点型</td></tr><tr><td align="left"><code>void</code></td><td align="left">无类型</td></tr></tbody></table>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="基本格式说明符"><a aria-hidden="true" tabindex="-1" href="#基本格式说明符"><span class="icon icon-link"></span></a>基本格式说明符</h3><div class="wrap-body">
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
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|
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|
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|
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|
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|
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|
||
<table><thead><tr><th>格式说明符</th><th>数据类型</th></tr></thead><tbody><tr><td><code>%d</code> 或 <code>%i</code></td><td><code>int</code> 整数</td></tr><tr><td><code>%f</code></td><td><code>float</code> 单精度的十进制类型</td></tr><tr><td><code>%lf</code></td><td><code>double</code> 高精度浮点数据或数字</td></tr><tr><td><code>%c</code></td><td><code>char</code> 字符</td></tr><tr><td><code>%s</code></td><td>用于 <code>strings</code> 字符串</td></tr></tbody></table>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="基本格式说明符-1"><a aria-hidden="true" tabindex="-1" href="#基本格式说明符-1"><span class="icon icon-link"></span></a>基本格式说明符</h3><div class="wrap-body">
|
||
|
||
|
||
|
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|
||
|
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|
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|
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|
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|
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|
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<table><thead><tr><th></th><th>short</th><th>int</th><th>long</th></tr></thead><tbody><tr><td>8 进制</td><td><code>%ho</code></td><td><code>%o</code></td><td><code>%lo</code></td></tr><tr><td>10 进制</td><td><code>%hd</code></td><td><code>%d</code></td><td><code>%ld</code></td></tr><tr><td>16 进制</td><td><code>%hx</code> / <code>%hX</code></td><td><code>%x</code> / <code>%X</code></td><td><code>%lx</code> / <code>%lX</code></td></tr></tbody></table>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="数据格式示例"><a aria-hidden="true" tabindex="-1" href="#数据格式示例"><span class="icon icon-link"></span></a>数据格式示例</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> myNum <span class="token operator">=</span> <span class="token number">5</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">float</span> myFloatNum <span class="token operator">=</span> <span class="token number">5.99</span><span class="token punctuation">;</span> <span class="token comment">// 浮点数</span>
|
||
</span><span class="code-line"><span class="token keyword">char</span> myLetter <span class="token operator">=</span> <span class="token char">'D'</span><span class="token punctuation">;</span> <span class="token comment">// 字符串</span>
|
||
</span><span class="code-line"><span class="token comment">// 打印输出变量</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d\n"</span><span class="token punctuation">,</span> myNum<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%f\n"</span><span class="token punctuation">,</span> myFloatNum<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%c\n"</span><span class="token punctuation">,</span> myLetter<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="预处理器"><a aria-hidden="true" tabindex="-1" href="#预处理器"><span class="icon icon-link"></span></a>预处理器</h2><div class="wrap-body">
|
||
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="预处理器指令"><a aria-hidden="true" tabindex="-1" href="#预处理器指令"><span class="icon icon-link"></span></a>预处理器指令</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=row-span-2-->
|
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|
||
<table><thead><tr><th>指令</th><th>描述</th></tr></thead><tbody><tr><td><code>#define</code></td><td>定义宏</td></tr><tr><td><code>#include</code></td><td>包含一个源代码文件</td></tr><tr><td><code>#undef</code></td><td>取消已定义的宏</td></tr><tr><td><code>#ifdef</code></td><td>如果宏已经定义，则返回真</td></tr><tr><td><code>#ifndef</code></td><td>如果宏没有定义，则返回真</td></tr><tr><td><code>#if</code></td><td>如果给定条件为真，则编译下面代码</td></tr><tr><td><code>#else</code></td><td><code>#if</code> 的替代方案</td></tr><tr><td><code>#elif</code></td><td>如果 <code>#if</code> 条件为假，当前条件为<code>真</code></td></tr><tr><td><code>#endif</code></td><td>结束一个 <code>#if……#else</code> 条件编译块</td></tr><tr><td><code>#error</code></td><td>当遇到标准错误时，输出错误消息</td></tr><tr><td><code>#pragma</code></td><td>使用标准化方法，向编译器发布特殊的命令到编译器中</td></tr></tbody></table>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token comment">// 所有的 MAX_ARRAY_LENGTH 替换为 20</span>
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">define</span> <span class="token macro-name">MAX_ARRAY_LENGTH</span> <span class="token expression"><span class="token number">20</span></span></span>
|
||
</span><span class="code-line"><span class="token comment">// 系统库中获取 stdio.h</span>
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line"><span class="token comment">// 本地目录中获取 myheader.h</span>
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string">"myheader.h"</span></span>
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">undef</span> <span class="token expression">FILE_SIZE</span></span>
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">define</span> <span class="token macro-name">FILE_SIZE</span> <span class="token expression"><span class="token number">42</span> </span><span class="token comment">// 取消已定义并定义为 42</span></span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="预定义宏"><a aria-hidden="true" tabindex="-1" href="#预定义宏"><span class="icon icon-link"></span></a>预定义宏</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
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||
|
||
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|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
<table class="style-list"><thead><tr><th>宏</th><th>描述</th></tr></thead><tbody><tr><td><code>__DATE__</code></td><td>当前日期，一个以 "MMM DD YYYY" 格式表示的字符常量</td></tr><tr><td><code>__TIME__</code></td><td>当前时间，一个以 "HH:MM:SS" 格式表示的字符常量</td></tr><tr><td><code>__FILE__</code></td><td>这会包含当前文件名，一个字符串常量</td></tr><tr><td><code>__LINE__</code></td><td>这会包含当前行号，一个十进制常量</td></tr><tr><td><code>__STDC__</code></td><td>当编译器以 <code>ANSI</code> 标准编译时，则定义为 <code>1</code></td></tr></tbody></table>
|
||
<!--rehype:className=style-list-->
|
||
<p><code>ANSI C</code> 定义了许多宏，您可以使用这些宏，但是不能直接修改这些预定义的宏</p>
|
||
<h4 id="预定义宏示例"><a aria-hidden="true" tabindex="-1" href="#预定义宏示例"><span class="icon icon-link"></span></a>预定义宏示例</h4>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"File :%s\n"</span><span class="token punctuation">,</span> <span class="token constant">__FILE__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Date :%s\n"</span><span class="token punctuation">,</span> <span class="token constant">__DATE__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Time :%s\n"</span><span class="token punctuation">,</span> <span class="token constant">__TIME__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Line :%d\n"</span><span class="token punctuation">,</span> <span class="token constant">__LINE__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"ANSI :%d\n"</span><span class="token punctuation">,</span> __STDC__<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="宏延续运算符"><a aria-hidden="true" tabindex="-1" href="#宏延续运算符"><span class="icon icon-link"></span></a>宏延续运算符（\）</h3><div class="wrap-body">
|
||
<p>一个宏通常写在一个单行上。</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">define</span> <span class="token macro-name function">message_for</span><span class="token expression"><span class="token punctuation">(</span>a<span class="token punctuation">,</span> b<span class="token punctuation">)</span> </span><span class="token punctuation">\</span>
|
||
</span></span><span class="code-line"><span class="token macro property"> <span class="token expression"><span class="token function">printf</span><span class="token punctuation">(</span>#a </span><span class="token string">" 和 "</span> <span class="token expression"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">b</span> </span></span><span class="token string">": 我们爱你！\n"</span><span class="token expression"><span class="token punctuation">)</span></span></span>
|
||
</span></code></pre>
|
||
<p>如果宏太长，一个单行容纳不下，则使用宏延续运算符 <code>\</code></p>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="字符串常量化运算符"><a aria-hidden="true" tabindex="-1" href="#字符串常量化运算符"><span class="icon icon-link"></span></a>字符串常量化运算符（#）</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">define</span> <span class="token macro-name function">message_for</span><span class="token expression"><span class="token punctuation">(</span>a<span class="token punctuation">,</span> b<span class="token punctuation">)</span> </span><span class="token punctuation">\</span>
|
||
</span></span><span class="code-line"><span class="token macro property"> <span class="token expression"><span class="token function">printf</span><span class="token punctuation">(</span>#a </span><span class="token string">" 和 "</span> <span class="token expression"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">b</span> </span></span><span class="token string">": 我们爱你！\n"</span><span class="token expression"><span class="token punctuation">)</span></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token keyword">void</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">message_for</span><span class="token punctuation">(</span>Carole<span class="token punctuation">,</span> Debra<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
<p>当上面的代码被编译和执行时，它会产生下列结果：</p>
|
||
<pre><code class="code-highlight"><span class="code-line">Carole 和 Debra: 我们爱你！
|
||
</span></code></pre>
|
||
<p>需要把一个宏的参数转换为字符串常量时，使用字符串常量化运算符 <code>#</code></p>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="标记粘贴运算符"><a aria-hidden="true" tabindex="-1" href="#标记粘贴运算符"><span class="icon icon-link"></span></a>标记粘贴运算符（##）</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">define</span> <span class="token macro-name function">tokenpaster</span><span class="token expression"><span class="token punctuation">(</span>n<span class="token punctuation">)</span> </span><span class="token punctuation">\</span>
|
||
</span></span><span class="code-line"><span class="token macro property"> <span class="token expression"><span class="token function">printf</span> <span class="token punctuation">(</span></span><span class="token string">"token"</span> <span class="token expression"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">n</span> </span></span><span class="token string">" = %d"</span><span class="token expression"><span class="token punctuation">,</span> token</span><span class="token punctuation">##</span><span class="token expression">n<span class="token punctuation">)</span></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token keyword">void</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">int</span> token34 <span class="token operator">=</span> <span class="token number">40</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">tokenpaster</span><span class="token punctuation">(</span><span class="token number">34</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="defined-运算符"><a aria-hidden="true" tabindex="-1" href="#defined-运算符"><span class="icon icon-link"></span></a>defined() 运算符</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">if</span> <span class="token expression"><span class="token operator">!</span><span class="token function">defined</span> <span class="token punctuation">(</span>MESSAGE<span class="token punctuation">)</span></span></span>
|
||
</span><span class="code-line"> <span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">define</span> <span class="token macro-name">MESSAGE</span> <span class="token string">"You wish!"</span></span>
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">endif</span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token keyword">void</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"信息如下: %s\n"</span><span class="token punctuation">,</span> \
|
||
</span><span class="code-line"> MESSAGE<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="参数化的宏"><a aria-hidden="true" tabindex="-1" href="#参数化的宏"><span class="icon icon-link"></span></a>参数化的宏</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> <span class="token function">square</span><span class="token punctuation">(</span><span class="token keyword">int</span> x<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> x <span class="token operator">*</span> x<span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
<p>宏重写上面的代码，如下：</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">define</span> <span class="token macro-name function">square</span><span class="token expression"><span class="token punctuation">(</span>x<span class="token punctuation">)</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>x<span class="token punctuation">)</span> <span class="token operator">*</span> <span class="token punctuation">(</span>x<span class="token punctuation">)</span><span class="token punctuation">)</span></span></span>
|
||
</span></code></pre>
|
||
<p>宏名称和左圆括号之间不允许有空格</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">define</span> <span class="token macro-name function">MAX</span><span class="token expression"><span class="token punctuation">(</span>x<span class="token punctuation">,</span>y<span class="token punctuation">)</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>x<span class="token punctuation">)</span> <span class="token operator">></span> <span class="token punctuation">(</span>y<span class="token punctuation">)</span> <span class="token operator">?</span> <span class="token punctuation">(</span>x<span class="token punctuation">)</span> <span class="token operator">:</span> <span class="token punctuation">(</span>y<span class="token punctuation">)</span><span class="token punctuation">)</span></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token keyword">void</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"20 到 10 之间的最大值是 %d\n"</span><span class="token punctuation">,</span> \
|
||
</span><span class="code-line"> <span class="token function">MAX</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">,</span> <span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="warning-和-error"><a aria-hidden="true" tabindex="-1" href="#warning-和-error"><span class="icon icon-link"></span></a>Warning 和 Error</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
<p>在 C 语言中，警告（Warning）和错误（Error）是编译器用于标识代码潜在问题或阻止代码编译的两种机制</p>
|
||
<p><strong>警告</strong>：<br>
|
||
警告提示代码中可能存在的问题，但不会阻止代码编译。处理警告可以提升代码质量和可移植性。</p>
|
||
<p><strong>常见警告示例</strong>：</p>
|
||
<ol>
|
||
<li>未使用的变量<br>
|
||
<code>int x; printf("%d",x);</code></li>
|
||
<li>类型隐式转换（可能导致数据丢失）
|
||
<code>int x = 3.14; //浮点数被隐式转换</code><br>
|
||
<code>int a = 2147483647 + 1; //可能溢出</code></li>
|
||
<li>函数声明与定义不匹配</li>
|
||
</ol>
|
||
<p><strong>错误</strong>：<br>
|
||
警告提示代码中可能存在的问题，但不会阻止代码编译。处理警告可以提升代码质量和可移植性。</p>
|
||
<p><strong>常见错误示例</strong>：</p>
|
||
<ol>
|
||
<li>语法错误（如缺少分号）<br>
|
||
<code>int x=1 </code></li>
|
||
<li>函数定义冲突</li>
|
||
</ol>
|
||
<pre class="language-c"><code class="language-C code-highlight"><span class="code-line"><span class="token keyword">void</span> <span class="token function">func</span><span class="token punctuation">(</span><span class="token keyword">int</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">void</span> <span class="token function">func</span><span class="token punctuation">(</span><span class="token keyword">double</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
<ol start="3">
|
||
<li>函数或变量未定义<br>
|
||
<code>y = 10; printf("%d",y);</code></li>
|
||
<li>头文件缺失或冲突<br>
|
||
<code>#include <unknown.h></code></li>
|
||
</ol>
|
||
<p><strong>使用编译器指令控制警告和错误</strong>:</p>
|
||
<ol>
|
||
<li>抑制警告<br>
|
||
可以使用编译器选项来关闭特定的警告，例如在 GCC 中：</li>
|
||
</ol>
|
||
<pre><code class="language-GCC code-highlight"><span class="code-line">gcc -w file.c # 禁用所有警告
|
||
</span><span class="code-line">gcc -Wall file.c # 启用所有常见警告
|
||
</span><span class="code-line">gcc -Werror file.c # 将警告视为错误
|
||
</span></code></pre>
|
||
<ol start="2">
|
||
<li>使用 #pragma 控制警告
|
||
在某些编译器中，可以使用<code>#pragma</code>指令启用或禁用警告</li>
|
||
</ol>
|
||
<pre class="language-c"><code class="language-C code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">pragma</span> <span class="token expression"><span class="token function">warning</span><span class="token punctuation">(</span>disable <span class="token operator">:</span> <span class="token number">4996</span><span class="token punctuation">)</span> </span><span class="token comment">// 禁用警告（适用于 MSVC 编译器）</span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Hello, world!"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
<p><strong>总结</strong></p>
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
<table><thead><tr><th>区别点</th><th>Warning（警告）</th><th>Error（错误）</th></tr></thead><tbody><tr><td>严重程度</td><td>程序可继续编译，但可能存在隐患</td><td>编译无法完成，必须修复</td></tr><tr><td>编译结果</td><td>生成可执行文件</td><td>无法生成可执行文件</td></tr><tr><td>触发原因</td><td>潜在问题，例如隐式转换或未使用的变量</td><td>语法或语义错误，例如语法错误或未定义变量</td></tr><tr><td>修复必要性</td><td>可选择修复，但建议修复以避免潜在问题</td><td>必须修复才能继续编译</td></tr><tr><td>编译器选项调整</td><td>可以忽略或转换为错误（如 <code>-Werror</code>）</td><td>无法调整，必须修复</td></tr></tbody></table>
|
||
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="函数"><a aria-hidden="true" tabindex="-1" href="#函数"><span class="icon icon-link"></span></a>函数</h2><div class="wrap-body">
|
||
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="函数声明和定义"><a aria-hidden="true" tabindex="-1" href="#函数声明和定义"><span class="icon icon-link"></span></a>函数声明和定义</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Hello World!"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
<p>函数由两部分组成</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">void</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment">// 声明 declaration</span>
|
||
</span><span class="code-line"> <span class="token comment">// 函数体（要执行的代码）(definition)</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
<hr>
|
||
<ul>
|
||
<li><code>Declaration</code> 声明函数名称、返回类型和参数 <em>(如果有)</em></li>
|
||
<li><code>Definition</code> 函数体 <em>(要执行的代码)</em></li>
|
||
</ul>
|
||
<hr>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token comment">// 函数声明</span>
|
||
</span><span class="code-line"><span class="token keyword">void</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 主要方法</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// --> 调用函数</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token keyword">void</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token comment">// 函数定义</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"晚上好！"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="调用函数"><a aria-hidden="true" tabindex="-1" href="#调用函数"><span class="icon icon-link"></span></a>调用函数</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token comment">// 创建函数</span>
|
||
</span><span class="code-line"><span class="token keyword">void</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"晚上好！"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 调用函数</span>
|
||
</span><span class="code-line"> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 可以被多次调用</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 -> "晚上好！"</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 -> "晚上好！"</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="函数参数"><a aria-hidden="true" tabindex="-1" href="#函数参数"><span class="icon icon-link"></span></a>函数参数</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">void</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token keyword">char</span> name<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Hello %s\n"</span><span class="token punctuation">,</span> name<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token string">"Liam"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token string">"Jenny"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">// Hello Liam</span>
|
||
</span><span class="code-line"><span class="token comment">// Hello Jenny</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="多个参数"><a aria-hidden="true" tabindex="-1" href="#多个参数"><span class="icon icon-link"></span></a>多个参数</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">void</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token keyword">char</span> name<span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token keyword">int</span> age<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"你好 %s 你 %d 岁了。\n"</span><span class="token punctuation">,</span>name<span class="token punctuation">,</span>age<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token string">"Liam"</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token string">"Jenny"</span><span class="token punctuation">,</span> <span class="token number">14</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">// 你好 Liam 你 3 岁了。</span>
|
||
</span><span class="code-line"><span class="token comment">// 你好 Jenny 你 14 岁了。</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="返回值"><a aria-hidden="true" tabindex="-1" href="#返回值"><span class="icon icon-link"></span></a>返回值</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token keyword">int</span> x<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">5</span> <span class="token operator">+</span> x<span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"结果: %d"</span><span class="token punctuation">,</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出 8 (5 + 3)</span>
|
||
</span></code></pre>
|
||
<p>两个参数</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token keyword">int</span> x<span class="token punctuation">,</span> <span class="token keyword">int</span> y<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> x <span class="token operator">+</span> y<span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"结果: %d"</span><span class="token punctuation">,</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token comment">// 将结果存储在变量中</span>
|
||
</span><span class="code-line"> <span class="token keyword">int</span> result <span class="token operator">=</span> <span class="token function">myFunction</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"结果 = %d"</span><span class="token punctuation">,</span> result<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">// 结果: 8 (5 + 3)</span>
|
||
</span><span class="code-line"><span class="token comment">// 结果 = 8 (5 + 3)</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="递归示例"><a aria-hidden="true" tabindex="-1" href="#递归示例"><span class="icon icon-link"></span></a>递归示例</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> <span class="token function">sum</span><span class="token punctuation">(</span><span class="token keyword">int</span> k<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">int</span> result <span class="token operator">=</span> <span class="token function">sum</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d"</span><span class="token punctuation">,</span> result<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">sum</span><span class="token punctuation">(</span><span class="token keyword">int</span> k<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">if</span> <span class="token punctuation">(</span>k <span class="token operator">></span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> k <span class="token operator">+</span> <span class="token function">sum</span><span class="token punctuation">(</span>k <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="数学函数"><a aria-hidden="true" tabindex="-1" href="#数学函数"><span class="icon icon-link"></span></a>数学函数</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><math.h></span></span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%f"</span><span class="token punctuation">,</span> <span class="token function">sqrt</span><span class="token punctuation">(</span><span class="token number">16</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 平方根</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%f"</span><span class="token punctuation">,</span> <span class="token function">ceil</span><span class="token punctuation">(</span><span class="token number">1.4</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 四舍五入 (入)</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%f"</span><span class="token punctuation">,</span> <span class="token function">floor</span><span class="token punctuation">(</span><span class="token number">1.4</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 四舍五入 (舍)</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%f"</span><span class="token punctuation">,</span> <span class="token function">pow</span><span class="token punctuation">(</span><span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// x(4)的y(3)次方</span>
|
||
</span></code></pre>
|
||
<hr>
|
||
<ul class="cols-2">
|
||
<li><code>abs(x)</code> 绝对值</li>
|
||
<li><code>acos(x)</code> 反余弦值</li>
|
||
<li><code>asin(x)</code> 反正弦值</li>
|
||
<li><code>atan(x)</code> 反正切</li>
|
||
<li><code>cbrt(x)</code> 立方根</li>
|
||
<li><code>cos(x)</code> 余弦</li>
|
||
<li><code>exp(x)</code> Ex 的值</li>
|
||
<li><code>sin(x)</code> x 的正弦值</li>
|
||
<li><code>tan(x)</code> 角度的正切</li>
|
||
</ul>
|
||
<!--rehype:className=cols-2-->
|
||
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="structures-结构"><a aria-hidden="true" tabindex="-1" href="#structures-结构"><span class="icon icon-link"></span></a>Structures 结构</h2><div class="wrap-body">
|
||
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="创建结构"><a aria-hidden="true" tabindex="-1" href="#创建结构"><span class="icon icon-link"></span></a>创建结构</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">MyStructure</span> <span class="token punctuation">{</span> <span class="token comment">// 结构声明</span>
|
||
</span><span class="code-line"> <span class="token keyword">int</span> myNum<span class="token punctuation">;</span> <span class="token comment">// 成员（int 变量）</span>
|
||
</span><span class="code-line"> <span class="token keyword">char</span> myLetter<span class="token punctuation">;</span> <span class="token comment">// 成员（char 变量）</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span> <span class="token comment">// 用分号结束结构</span>
|
||
</span></code></pre>
|
||
<p>创建一个名为 <code>s1</code> 的结构变量</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">myStructure</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">int</span> myNum<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">char</span> myLetter<span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line highlight-line"> <span class="token keyword">struct</span> <span class="token class-name">myStructure</span> s1<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="结构中的字符串"><a aria-hidden="true" tabindex="-1" href="#结构中的字符串"><span class="icon icon-link"></span></a>结构中的字符串</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">myStructure</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">int</span> myNum<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">char</span> myLetter<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">char</span> myString<span class="token punctuation">[</span><span class="token number">30</span><span class="token punctuation">]</span><span class="token punctuation">;</span> <span class="token comment">// String</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">struct</span> <span class="token class-name">myStructure</span> s1<span class="token punctuation">;</span>
|
||
</span><span class="code-line highlight-line"> <span class="token function">strcpy</span><span class="token punctuation">(</span>s1<span class="token punctuation">.</span>myString<span class="token punctuation">,</span> <span class="token string">"Some text"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token comment">// 打印值</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"我字符串: %s"</span><span class="token punctuation">,</span> s1<span class="token punctuation">.</span>myString<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
<p>使用 <code>strcpy</code> 函数为字符串赋值</p>
|
||
</div></div></div><div class="wrap h3body-not-exist row-span-2"><div class="wrap-header h3wrap"><h3 id="访问结构成员"><a aria-hidden="true" tabindex="-1" href="#访问结构成员"><span class="icon icon-link"></span></a>访问结构成员</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token comment">// 创建一个名为 myStructure 的结构</span>
|
||
</span><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">myStructure</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">int</span> myNum<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">char</span> myLetter<span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token comment">// 创建一个名为 s1 的 myStructure 结构变量</span>
|
||
</span><span class="code-line"> <span class="token keyword">struct</span> <span class="token class-name">myStructure</span> s1<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token comment">// 为 s1 的成员赋值</span>
|
||
</span><span class="code-line highlight-line"> s1<span class="token punctuation">.</span>myNum <span class="token operator">=</span> <span class="token number">13</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line highlight-line"> s1<span class="token punctuation">.</span>myLetter <span class="token operator">=</span> <span class="token char">'B'</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"> <span class="token comment">// 创建一个名为 s2 的 myStructure 结构变量</span>
|
||
</span><span class="code-line"> <span class="token comment">// 并为其赋值</span>
|
||
</span><span class="code-line highlight-line"> <span class="token keyword">struct</span> <span class="token class-name">myStructure</span> s2 <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">13</span><span class="token punctuation">,</span> <span class="token char">'B'</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token comment">// 打印值</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"My number: %d\n"</span><span class="token punctuation">,</span> s1<span class="token punctuation">.</span>myNum<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"My letter: %c\n"</span><span class="token punctuation">,</span> s1<span class="token punctuation">.</span>myLetter<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
<p>创建不同的结构变量</p>
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">myStructure</span> s1<span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">myStructure</span> s2<span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 为不同的结构变量赋值</span>
|
||
</span><span class="code-line">s1<span class="token punctuation">.</span>myNum <span class="token operator">=</span> <span class="token number">13</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">s1<span class="token punctuation">.</span>myLetter <span class="token operator">=</span> <span class="token char">'B'</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line">s2<span class="token punctuation">.</span>myNum <span class="token operator">=</span> <span class="token number">20</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">s2<span class="token punctuation">.</span>myLetter <span class="token operator">=</span> <span class="token char">'C'</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="复制结构"><a aria-hidden="true" tabindex="-1" href="#复制结构"><span class="icon icon-link"></span></a>复制结构</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">myStructure</span> s1 <span class="token operator">=</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token number">13</span><span class="token punctuation">,</span> <span class="token char">'B'</span><span class="token punctuation">,</span> <span class="token string">"Some text"</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">myStructure</span> s2<span class="token punctuation">;</span>
|
||
</span><span class="code-line highlight-line">s2 <span class="token operator">=</span> s1<span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
<p>示例中，将 <code>s1</code> 的值复制到 <code>s2</code></p>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="修改值"><a aria-hidden="true" tabindex="-1" href="#修改值"><span class="icon icon-link"></span></a>修改值</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token comment">// 创建一个结构变量并为其赋值</span>
|
||
</span><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">myStructure</span> s1 <span class="token operator">=</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token number">13</span><span class="token punctuation">,</span> <span class="token char">'B'</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 修改值</span>
|
||
</span><span class="code-line highlight-line">s1<span class="token punctuation">.</span>myNum <span class="token operator">=</span> <span class="token number">30</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line highlight-line">s1<span class="token punctuation">.</span>myLetter <span class="token operator">=</span> <span class="token char">'C'</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token comment">// 打印值</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%d %c %s"</span><span class="token punctuation">,</span>
|
||
</span><span class="code-line"> s1<span class="token punctuation">.</span>myNum<span class="token punctuation">,</span>
|
||
</span><span class="code-line"> s1<span class="token punctuation">.</span>myLetter<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="文件处理"><a aria-hidden="true" tabindex="-1" href="#文件处理"><span class="icon icon-link"></span></a>文件处理</h2><div class="wrap-body">
|
||
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="文件处理函数"><a aria-hidden="true" tabindex="-1" href="#文件处理函数"><span class="icon icon-link"></span></a>文件处理函数</h3><div class="wrap-body">
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
<table><thead><tr><th>函数</th><th>描述 Description</th></tr></thead><tbody><tr><td><code>fopen()</code></td><td><code>打开</code>新文件或现有文件</td></tr><tr><td><code>fprintf()</code></td><td>将数据<code>写入</code>文件</td></tr><tr><td><code>fscanf()</code></td><td>从文件中<code>读取</code>数据</td></tr><tr><td><code>fputc()</code></td><td>将一个字符<code>写入</code>文件</td></tr><tr><td><code>fgetc()</code></td><td>从文件中<code>读取</code>一个字符</td></tr><tr><td><code>fclose()</code></td><td><code>关闭</code>文件</td></tr><tr><td><code>fseek()</code></td><td>将文件指针设置到<code>给定位置</code></td></tr><tr><td><code>fputw()</code></td><td>将整数<code>写入</code>文件</td></tr><tr><td><code>fgetw()</code></td><td>从文件中<code>读取</code>一个整数</td></tr><tr><td><code>ftell()</code></td><td>返回当前<code>位置</code></td></tr><tr><td><code>rewind()</code></td><td>将文件指针设置为文件的开头</td></tr></tbody></table>
|
||
<p>C 库中有许多函数可以<code>打开</code>/<code>读取</code>/<code>写入</code>/<code>搜索</code>和<code>关闭</code>文件</p>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="打开模式参数"><a aria-hidden="true" tabindex="-1" href="#打开模式参数"><span class="icon icon-link"></span></a>打开模式参数</h3><div class="wrap-body">
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
<table><thead><tr><th>模式 Mode</th><th>描述 Description</th></tr></thead><tbody><tr><td><code>r</code></td><td>以<code>读取</code>模式打开一个文本文件，允许读取文件</td></tr><tr><td><code>w</code></td><td>以<code>写</code>模式打开一个文本文件，允许写入文件</td></tr><tr><td><code>a</code></td><td>以<code>追加</code>模式打开一个文本文件<br>如果文件不存在，则会创建一个新文件</td></tr><tr><td><code>r+</code></td><td>以<code>读写</code>模式打开一个文本文件，允许读写文件</td></tr><tr><td><code>w+</code></td><td>以<code>读写</code>模式打开一个文本文件，允许读写文件</td></tr><tr><td><code>a+</code></td><td>以<code>读写</code>模式打开一个文本文件，允许读写文件</td></tr><tr><td><code>rb</code></td><td>以<code>读取</code>模式打开二进制文件</td></tr><tr><td><code>wb</code></td><td>以<code>写入</code>模式打开二进制文件</td></tr><tr><td><code>ab</code></td><td>以<code>追加</code>模式打开二进制文件</td></tr><tr><td><code>rb+</code></td><td>以<code>读写</code>模式打开二进制文件</td></tr><tr><td><code>wb+</code></td><td>以<code>读写</code>模式打开二进制文件</td></tr><tr><td><code>ab+</code></td><td>以<code>读写</code>模式打开二进制文件</td></tr></tbody></table>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="打开文件fopen"><a aria-hidden="true" tabindex="-1" href="#打开文件fopen"><span class="icon icon-link"></span></a>打开文件：fopen()</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span><span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> FILE <span class="token operator">*</span>fp<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">char</span> ch<span class="token punctuation">;</span>
|
||
</span><span class="code-line highlight-line"> fp <span class="token operator">=</span> <span class="token function">fopen</span><span class="token punctuation">(</span><span class="token string">"file_handle.c"</span><span class="token punctuation">,</span> <span class="token string">"r"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"> <span class="token keyword">while</span> <span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> ch <span class="token operator">=</span> <span class="token function">fgetc</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">if</span> <span class="token punctuation">(</span>ch <span class="token operator">==</span> <span class="token constant">EOF</span><span class="token punctuation">)</span>
|
||
</span><span class="code-line"> <span class="token keyword">break</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%c"</span><span class="token punctuation">,</span> ch<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token punctuation">}</span>
|
||
</span><span class="code-line"> <span class="token function">fclose</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
<p>对文件执行所有操作后，必须关闭 <code>fclose()</code> 该文件</p>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="写入文件fprintf"><a aria-hidden="true" tabindex="-1" href="#写入文件fprintf"><span class="icon icon-link"></span></a>写入文件：fprintf()</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> FILE <span class="token operator">*</span>fp<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> fp <span class="token operator">=</span> <span class="token function">fopen</span><span class="token punctuation">(</span><span class="token string">"file.txt"</span><span class="token punctuation">,</span> <span class="token string">"w"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 打开文件</span>
|
||
</span><span class="code-line"> <span class="token comment">// 将数据写入文件</span>
|
||
</span><span class="code-line highlight-line"> <span class="token function">fprintf</span><span class="token punctuation">(</span>fp<span class="token punctuation">,</span> <span class="token string">"fprintf 的 Hello 文件..\n"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">fclose</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 关闭文件 </span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="读取文件fscanf"><a aria-hidden="true" tabindex="-1" href="#读取文件fscanf"><span class="icon icon-link"></span></a>读取文件：fscanf()</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><stdio.h></span> </span>
|
||
</span><span class="code-line"><span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
|
||
</span><span class="code-line"> FILE <span class="token operator">*</span>fp<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">char</span> buff<span class="token punctuation">[</span><span class="token number">255</span><span class="token punctuation">]</span><span class="token punctuation">;</span> <span class="token comment">// 创建char数组存储文件数据</span>
|
||
</span><span class="code-line"> fp <span class="token operator">=</span> <span class="token function">fopen</span><span class="token punctuation">(</span><span class="token string">"file.txt"</span><span class="token punctuation">,</span> <span class="token string">"r"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line highlight-line"> <span class="token keyword">while</span><span class="token punctuation">(</span><span class="token function">fscanf</span><span class="token punctuation">(</span>fp<span class="token punctuation">,</span> <span class="token string">"%s"</span><span class="token punctuation">,</span> buff<span class="token punctuation">)</span><span class="token operator">!=</span><span class="token constant">EOF</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%s "</span><span class="token punctuation">,</span> buff<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token punctuation">}</span>
|
||
</span><span class="code-line"> <span class="token function">fclose</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="写入文件fputc"><a aria-hidden="true" tabindex="-1" href="#写入文件fputc"><span class="icon icon-link"></span></a>写入文件：fputc()</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
|
||
</span><span class="code-line"> FILE <span class="token operator">*</span>fp<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> fp <span class="token operator">=</span> <span class="token function">fopen</span><span class="token punctuation">(</span><span class="token string">"file1.txt"</span><span class="token punctuation">,</span> <span class="token string">"w"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 打开文件</span>
|
||
</span><span class="code-line highlight-line"> <span class="token function">fputc</span><span class="token punctuation">(</span><span class="token char">'a'</span><span class="token punctuation">,</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 将单个字符写入文件</span>
|
||
</span><span class="code-line"> <span class="token function">fclose</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 关闭文件</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="读取文件fgetc"><a aria-hidden="true" tabindex="-1" href="#读取文件fgetc"><span class="icon icon-link"></span></a>读取文件：fgetc()</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span><span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span><span class="token string"><conio.h></span></span>
|
||
</span><span class="code-line"><span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> FILE <span class="token operator">*</span>fp<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">char</span> c<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">clrscr</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> fp<span class="token operator">=</span><span class="token function">fopen</span><span class="token punctuation">(</span><span class="token string">"myfile.txt"</span><span class="token punctuation">,</span> <span class="token string">"r"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line highlight-line"> <span class="token keyword">while</span><span class="token punctuation">(</span><span class="token punctuation">(</span>c<span class="token operator">=</span><span class="token function">fgetc</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token operator">!=</span><span class="token constant">EOF</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%c"</span><span class="token punctuation">,</span> c<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token punctuation">}</span>
|
||
</span><span class="code-line"> <span class="token function">fclose</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">getch</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="写入文件fputs"><a aria-hidden="true" tabindex="-1" href="#写入文件fputs"><span class="icon icon-link"></span></a>写入文件：fputs()</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span><span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span><span class="token string"><conio.h></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
|
||
</span><span class="code-line"> FILE <span class="token operator">*</span>fp<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">clrscr</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> fp <span class="token operator">=</span> <span class="token function">fopen</span><span class="token punctuation">(</span><span class="token string">"myfile2.txt"</span><span class="token punctuation">,</span><span class="token string">"w"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line highlight-line"> <span class="token function">fputs</span><span class="token punctuation">(</span><span class="token string">"hello c programming"</span><span class="token punctuation">,</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">fclose</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">getch</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="读取文件fgets"><a aria-hidden="true" tabindex="-1" href="#读取文件fgets"><span class="icon icon-link"></span></a>读取文件：fgets()</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span><span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span><span class="token string"><conio.h></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> FILE <span class="token operator">*</span>fp<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">char</span> text<span class="token punctuation">[</span><span class="token number">300</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">clrscr</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"> fp<span class="token operator">=</span><span class="token function">fopen</span><span class="token punctuation">(</span><span class="token string">"myfile2.txt"</span><span class="token punctuation">,</span> <span class="token string">"r"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line highlight-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%s"</span><span class="token punctuation">,</span> <span class="token function">fgets</span><span class="token punctuation">(</span>text<span class="token punctuation">,</span> <span class="token number">200</span><span class="token punctuation">,</span> fp<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">fclose</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">getch</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="fseek"><a aria-hidden="true" tabindex="-1" href="#fseek"><span class="icon icon-link"></span></a>fseek()</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line"><span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
|
||
</span><span class="code-line"> FILE <span class="token operator">*</span>fp<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> fp <span class="token operator">=</span> <span class="token function">fopen</span><span class="token punctuation">(</span><span class="token string">"myfile.txt"</span><span class="token punctuation">,</span><span class="token string">"w+"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">fputs</span><span class="token punctuation">(</span><span class="token string">"This is Book"</span><span class="token punctuation">,</span> fp<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"> <span class="token comment">// 将文件指针设置到给定位置</span>
|
||
</span><span class="code-line highlight-line"> <span class="token function">fseek</span><span class="token punctuation">(</span>fp<span class="token punctuation">,</span> <span class="token number">7</span><span class="token punctuation">,</span> <span class="token constant">SEEK_SET</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">fputs</span><span class="token punctuation">(</span><span class="token string">"Kenny Wong"</span><span class="token punctuation">,</span> fp<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">fclose</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
<p>将文件指针设置到给定位置</p>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="rewind"><a aria-hidden="true" tabindex="-1" href="#rewind"><span class="icon icon-link"></span></a>rewind()</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span><span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span><span class="token string"><conio.h></span></span>
|
||
</span><span class="code-line"><span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
|
||
</span><span class="code-line"> FILE <span class="token operator">*</span>fp<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">char</span> c<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">clrscr</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> fp<span class="token operator">=</span><span class="token function">fopen</span><span class="token punctuation">(</span><span class="token string">"file.txt"</span><span class="token punctuation">,</span> <span class="token string">"r"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">while</span><span class="token punctuation">(</span><span class="token punctuation">(</span>c<span class="token operator">=</span><span class="token function">fgetc</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token constant">EOF</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%c"</span><span class="token punctuation">,</span> c<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token punctuation">}</span>
|
||
</span><span class="code-line highlight-line"> <span class="token function">rewind</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 将文件指针移动到文件的开头</span>
|
||
</span><span class="code-line"> <span class="token keyword">while</span><span class="token punctuation">(</span><span class="token punctuation">(</span>c<span class="token operator">=</span><span class="token function">fgetc</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token constant">EOF</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"%c"</span><span class="token punctuation">,</span> c<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token punctuation">}</span>
|
||
</span><span class="code-line"> <span class="token function">fclose</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">getch</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出</span>
|
||
</span><span class="code-line"><span class="token comment">// Hello World!Hello World!</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="ftell"><a aria-hidden="true" tabindex="-1" href="#ftell"><span class="icon icon-link"></span></a>ftell()</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><stdio.h></span></span>
|
||
</span><span class="code-line"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">include</span> <span class="token string"><conio.h></span></span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">void</span> <span class="token function">main</span> <span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
|
||
</span><span class="code-line"> FILE <span class="token operator">*</span>fp<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token keyword">int</span> length<span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">clrscr</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> fp <span class="token operator">=</span> <span class="token function">fopen</span><span class="token punctuation">(</span><span class="token string">"file.txt"</span><span class="token punctuation">,</span> <span class="token string">"r"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">fseek</span><span class="token punctuation">(</span>fp<span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token constant">SEEK_END</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line highlight-line"> length <span class="token operator">=</span> <span class="token function">ftell</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 返回当前位置</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"> <span class="token function">fclose</span><span class="token punctuation">(</span>fp<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"文件大小: %d bytes"</span><span class="token punctuation">,</span> length<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">getch</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token comment">// 输出</span>
|
||
</span><span class="code-line"><span class="token comment">// 文件大小: 18 bytes</span>
|
||
</span></code></pre>
|
||
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="c-网络编程"><a aria-hidden="true" tabindex="-1" href="#c-网络编程"><span class="icon icon-link"></span></a>C 网络编程</h2><div class="wrap-body">
|
||
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="网络编程介绍"><a aria-hidden="true" tabindex="-1" href="#网络编程介绍"><span class="icon icon-link"></span></a>网络编程介绍</h3><div class="wrap-body">
|
||
<p>C使用sockets进行网络通信。包含头文件：</p>
|
||
<ul>
|
||
<li><code>#include <sys/socket.h></code>: 套接字操作，如创建、绑定和监听套接字</li>
|
||
<li><code>#include <arpa/inet.h></code>: IP 地址转换</li>
|
||
<li><code>#include <unistd.h></code>: 关闭套接字等</li>
|
||
<li><code>#include <netinet/in.h></code>: 网络地址结构定义和相关敞亮</li>
|
||
</ul>
|
||
</div></div></div><div class="wrap h3body-exist"><div class="wrap-header h3wrap"><h3 id="创建套接字"><a aria-hidden="true" tabindex="-1" href="#创建套接字"><span class="icon icon-link"></span></a>创建套接字</h3><div class="wrap-body">
|
||
<p>网络通信的第一步是创建套接字。套接字是网络通信的基础，通过它可以与远程主机进行数据交换。</p>
|
||
<h4 id="服务端"><a aria-hidden="true" tabindex="-1" href="#服务端"><span class="icon icon-link"></span></a>服务端</h4>
|
||
<pre class="language-cpp"><code class="language-cpp code-highlight"><span class="code-line"><span class="token keyword">int</span> server_fd<span class="token punctuation">,</span> new_socket<span class="token punctuation">;</span> <span class="token comment">// 定义服务器文件描述符和新连接的套接字</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> port <span class="token operator">=</span> <span class="token number">8080</span><span class="token punctuation">;</span> <span class="token comment">// 服务器使用的端口号</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 创建套接字文件描述符</span>
|
||
</span><span class="code-line"><span class="token comment">// AF_INET 表示使用 IPv4 协议，SOCK_STREAM 表示使用 TCP 协议，协议参数通常为 0（默认 TCP）</span>
|
||
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>server_fd <span class="token operator">=</span> <span class="token function">socket</span><span class="token punctuation">(</span>AF_INET<span class="token punctuation">,</span> SOCK_STREAM<span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">perror</span><span class="token punctuation">(</span><span class="token string">"socket failed"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">exit</span><span class="token punctuation">(</span>EXIT_FAILURE<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
<h4 id="客户端"><a aria-hidden="true" tabindex="-1" href="#客户端"><span class="icon icon-link"></span></a>客户端</h4>
|
||
<pre class="language-cpp"><code class="language-cpp code-highlight"><span class="code-line"><span class="token keyword">int</span> sock <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> <span class="token comment">// 客户端的套接字描述符</span>
|
||
</span><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">sockaddr_in</span> serv_addr<span class="token punctuation">;</span> <span class="token comment">// 定义服务器地址结构体</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 创建套接字</span>
|
||
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>sock <span class="token operator">=</span> <span class="token function">socket</span><span class="token punctuation">(</span>AF_INET<span class="token punctuation">,</span> SOCK_STREAM<span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator"><</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">perror</span><span class="token punctuation">(</span><span class="token string">"Socket creation failed"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">exit</span><span class="token punctuation">(</span>EXIT_FAILURE<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-exist"><div class="wrap-header h3wrap"><h3 id="绑定套接字"><a aria-hidden="true" tabindex="-1" href="#绑定套接字"><span class="icon icon-link"></span></a>绑定套接字</h3><div class="wrap-body">
|
||
<p>服务端创建套接字后，需要将其绑定到特定的 IP 地址和端口，以便客户端能够连接。</p>
|
||
<h4 id="服务端-1"><a aria-hidden="true" tabindex="-1" href="#服务端-1"><span class="icon icon-link"></span></a>服务端</h4>
|
||
<pre class="language-cpp"><code class="language-cpp code-highlight"><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">sockaddr_in</span> address<span class="token punctuation">;</span> <span class="token comment">// 定义存储地址信息的结构体</span>
|
||
</span><span class="code-line">address<span class="token punctuation">.</span>sin_family <span class="token operator">=</span> AF_INET<span class="token punctuation">;</span> <span class="token comment">// 设置地址族为 IPv4</span>
|
||
</span><span class="code-line">address<span class="token punctuation">.</span>sin_addr<span class="token punctuation">.</span>s_addr <span class="token operator">=</span> INADDR_ANY<span class="token punctuation">;</span> <span class="token comment">// 将服务器绑定到所有可用的网络接口（即本机的所有 IP 地址）</span>
|
||
</span><span class="code-line">address<span class="token punctuation">.</span>sin_port <span class="token operator">=</span> <span class="token function">htons</span><span class="token punctuation">(</span>port<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 将端口号转换为网络字节序，大端模式</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 将套接字绑定到指定的地址和端口上</span>
|
||
</span><span class="code-line"><span class="token comment">// bind() 将服务器的文件描述符与 IP 地址和端口号进行绑定，以便客户端能够通过该地址和端口访问服务器</span>
|
||
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">bind</span><span class="token punctuation">(</span>server_fd<span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token keyword">struct</span> <span class="token class-name">sockaddr</span> <span class="token operator">*</span><span class="token punctuation">)</span><span class="token operator">&</span>address<span class="token punctuation">,</span> <span class="token keyword">sizeof</span><span class="token punctuation">(</span>address<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator"><</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">perror</span><span class="token punctuation">(</span><span class="token string">"bind failed"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">exit</span><span class="token punctuation">(</span>EXIT_FAILURE<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-exist"><div class="wrap-header h3wrap"><h3 id="监听和接收连接"><a aria-hidden="true" tabindex="-1" href="#监听和接收连接"><span class="icon icon-link"></span></a>监听和接收连接</h3><div class="wrap-body">
|
||
<p>服务端在绑定套接字之后，需要进入监听状态，以等待客户端的连接请求。</p>
|
||
<h4 id="服务端-2"><a aria-hidden="true" tabindex="-1" href="#服务端-2"><span class="icon icon-link"></span></a>服务端</h4>
|
||
<pre class="language-cpp"><code class="language-cpp code-highlight"><span class="code-line"><span class="token comment">// 开始监听客户端连接</span>
|
||
</span><span class="code-line"><span class="token comment">// 监听连接请求</span>
|
||
</span><span class="code-line"><span class="token comment">// listen() 函数将套接字设置为被动模式，准备接收来自客户端的连接请求</span>
|
||
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">listen</span><span class="token punctuation">(</span>server_fd<span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span> <span class="token operator"><</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment">// 第二个参数 3 表示连接请求的队列大小</span>
|
||
</span><span class="code-line"> <span class="token function">perror</span><span class="token punctuation">(</span><span class="token string">"listen failed"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">exit</span><span class="token punctuation">(</span>EXIT_FAILURE<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> addrlen <span class="token operator">=</span> <span class="token keyword">sizeof</span><span class="token punctuation">(</span>address<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 获取地址结构体的大小</span>
|
||
</span><span class="code-line"><span class="token comment">// accept() 函数会阻塞等待客户端的连接请求，一旦连接请求到来，创建一个新的套接字 new_socket 用于数据传输</span>
|
||
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>new_socket <span class="token operator">=</span> <span class="token function">accept</span><span class="token punctuation">(</span>server_fd<span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token keyword">struct</span> <span class="token class-name">sockaddr</span> <span class="token operator">*</span><span class="token punctuation">)</span><span class="token operator">&</span>address<span class="token punctuation">,</span> <span class="token punctuation">(</span>socklen_t<span class="token operator">*</span><span class="token punctuation">)</span><span class="token operator">&</span>addrlen<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator"><</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">perror</span><span class="token punctuation">(</span><span class="token string">"accept failed"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">exit</span><span class="token punctuation">(</span>EXIT_FAILURE<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-exist"><div class="wrap-header h3wrap"><h3 id="连接到服务端"><a aria-hidden="true" tabindex="-1" href="#连接到服务端"><span class="icon icon-link"></span></a>连接到服务端</h3><div class="wrap-body">
|
||
<p>客户端使用 <code>connect()</code> 函数连接到服务器的 IP 地址和端口。</p>
|
||
<h4 id="客户端-1"><a aria-hidden="true" tabindex="-1" href="#客户端-1"><span class="icon icon-link"></span></a>客户端</h4>
|
||
<pre class="language-cpp"><code class="language-cpp code-highlight"><span class="code-line"><span class="token comment">// 设置服务器地址</span>
|
||
</span><span class="code-line">serv_addr<span class="token punctuation">.</span>sin_family <span class="token operator">=</span> AF_INET<span class="token punctuation">;</span> <span class="token comment">// 设置地址族为 IPv4</span>
|
||
</span><span class="code-line">serv_addr<span class="token punctuation">.</span>sin_port <span class="token operator">=</span> <span class="token function">htons</span><span class="token punctuation">(</span>port<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 将端口号转换为网络字节序</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 将 IP 地址转换为二进制并存储在 serv_addr 结构体中</span>
|
||
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">inet_pton</span><span class="token punctuation">(</span>AF_INET<span class="token punctuation">,</span> <span class="token string">"127.0.0.1"</span><span class="token punctuation">,</span> <span class="token operator">&</span>serv_addr<span class="token punctuation">.</span>sin_addr<span class="token punctuation">)</span> <span class="token operator"><=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">perror</span><span class="token punctuation">(</span><span class="token string">"Invalid address/ Address not supported"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">exit</span><span class="token punctuation">(</span>EXIT_FAILURE<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 连接服务器</span>
|
||
</span><span class="code-line"><span class="token comment">// connect() 函数将客户端的套接字与服务器的地址绑定，从而建立连接</span>
|
||
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">connect</span><span class="token punctuation">(</span>sock<span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token keyword">struct</span> <span class="token class-name">sockaddr</span> <span class="token operator">*</span><span class="token punctuation">)</span><span class="token operator">&</span>serv_addr<span class="token punctuation">,</span> <span class="token keyword">sizeof</span><span class="token punctuation">(</span>serv_addr<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator"><</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">perror</span><span class="token punctuation">(</span><span class="token string">"Connection Failed"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"> <span class="token function">exit</span><span class="token punctuation">(</span>EXIT_FAILURE<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-exist"><div class="wrap-header h3wrap"><h3 id="发送和接收数据"><a aria-hidden="true" tabindex="-1" href="#发送和接收数据"><span class="icon icon-link"></span></a>发送和接收数据</h3><div class="wrap-body">
|
||
<p>一旦连接建立，服务端和客户端可以通过套接字发送和接收数据。</p>
|
||
<h4 id="服务端-3"><a aria-hidden="true" tabindex="-1" href="#服务端-3"><span class="icon icon-link"></span></a>服务端</h4>
|
||
<pre class="language-cpp"><code class="language-cpp code-highlight"><span class="code-line"><span class="token comment">// 服务端从客户端接收数据</span>
|
||
</span><span class="code-line"><span class="token keyword">char</span> buffer<span class="token punctuation">[</span><span class="token number">1024</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">0</span><span class="token punctuation">}</span><span class="token punctuation">;</span> <span class="token comment">// 缓冲区，用于存储接收的数据</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> valread <span class="token operator">=</span> <span class="token function">read</span><span class="token punctuation">(</span>new_socket<span class="token punctuation">,</span> buffer<span class="token punctuation">,</span> <span class="token number">1024</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 从客户端读取数据</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Client: %s\n"</span><span class="token punctuation">,</span> buffer<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 打印接收到的客户端数据</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 服务端发送响应数据给客户端</span>
|
||
</span><span class="code-line"><span class="token keyword">const</span> <span class="token keyword">char</span> <span class="token operator">*</span>response <span class="token operator">=</span> <span class="token string">"Hello from server"</span><span class="token punctuation">;</span> <span class="token comment">// 响应消息</span>
|
||
</span><span class="code-line"><span class="token function">send</span><span class="token punctuation">(</span>new_socket<span class="token punctuation">,</span> response<span class="token punctuation">,</span> <span class="token function">strlen</span><span class="token punctuation">(</span>response<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 发送数据到客户端</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Server message sent\n"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span></code></pre>
|
||
<h4 id="客户端-2"><a aria-hidden="true" tabindex="-1" href="#客户端-2"><span class="icon icon-link"></span></a>客户端</h4>
|
||
<pre class="language-cpp"><code class="language-cpp code-highlight"><span class="code-line"><span class="token comment">// 客户端发送数据给服务端</span>
|
||
</span><span class="code-line"><span class="token keyword">const</span> <span class="token keyword">char</span> <span class="token operator">*</span>message <span class="token operator">=</span> <span class="token string">"Hello from client"</span><span class="token punctuation">;</span> <span class="token comment">// 要发送的消息</span>
|
||
</span><span class="code-line"><span class="token function">send</span><span class="token punctuation">(</span>sock<span class="token punctuation">,</span> message<span class="token punctuation">,</span> <span class="token function">strlen</span><span class="token punctuation">(</span>message<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 发送数据到服务端</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Client message sent\n"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token comment">// 客户端从服务端接收响应数据</span>
|
||
</span><span class="code-line"><span class="token keyword">char</span> buffer<span class="token punctuation">[</span><span class="token number">1024</span><span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token number">0</span><span class="token punctuation">}</span><span class="token punctuation">;</span> <span class="token comment">// 缓冲区，用于存储接收到的数据</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> valread <span class="token operator">=</span> <span class="token function">read</span><span class="token punctuation">(</span>sock<span class="token punctuation">,</span> buffer<span class="token punctuation">,</span> <span class="token number">1024</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 读取服务端的响应数据</span>
|
||
</span><span class="code-line"><span class="token function">printf</span><span class="token punctuation">(</span><span class="token string">"Server: %s\n"</span><span class="token punctuation">,</span> buffer<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 打印接收到的服务端数据</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-exist"><div class="wrap-header h3wrap"><h3 id="关闭套接字"><a aria-hidden="true" tabindex="-1" href="#关闭套接字"><span class="icon icon-link"></span></a>关闭套接字</h3><div class="wrap-body">
|
||
<p>完成通信后，双方都应关闭各自的套接字以释放资源。</p>
|
||
<h4 id="服务端-4"><a aria-hidden="true" tabindex="-1" href="#服务端-4"><span class="icon icon-link"></span></a>服务端</h4>
|
||
<pre class="language-cpp"><code class="language-cpp code-highlight"><span class="code-line"><span class="token comment">// 关闭服务端套接字</span>
|
||
</span><span class="code-line"><span class="token function">close</span><span class="token punctuation">(</span>new_socket<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 关闭用于数据传输的客户端套接字</span>
|
||
</span><span class="code-line"><span class="token function">close</span><span class="token punctuation">(</span>server_fd<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 关闭服务器的监听套接字</span>
|
||
</span><span class="code-line">
|
||
</span></code></pre>
|
||
<h4 id="客户端-3"><a aria-hidden="true" tabindex="-1" href="#客户端-3"><span class="icon icon-link"></span></a>客户端</h4>
|
||
<pre class="language-cpp"><code class="language-cpp code-highlight"><span class="code-line"><span class="token comment">// 关闭客户端套接字</span>
|
||
</span><span class="code-line"><span class="token function">close</span><span class="token punctuation">(</span>sock<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 关闭客户端的套接字</span>
|
||
</span></code></pre>
|
||
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="io多路复用"><a aria-hidden="true" tabindex="-1" href="#io多路复用"><span class="icon icon-link"></span></a>I/O多路复用</h2><div class="wrap-body">
|
||
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="多路复用介绍"><a aria-hidden="true" tabindex="-1" href="#多路复用介绍"><span class="icon icon-link"></span></a>多路复用介绍</h3><div class="wrap-body">
|
||
<p>在网络编程中，服务端可以使用 I/O 多路复用 技术，如 <code>select</code>、<code>poll</code> 或 <code>epoll</code>。这些技术允许服务端同时监听多个文件描述符（如套接字），并在其中一个发生事件时进行处理，提升系统效率。包含头文件：</p>
|
||
<ul>
|
||
<li><code>#include <sys/select.h></code>: 提供 <code>select</code></li>
|
||
<li><code>#include <poll.h></code>: 提供 <code>poll</code></li>
|
||
<li><code>#include <sys/epoll.h></code>: 提供<code>epoll</code></li>
|
||
</ul>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="使用select"><a aria-hidden="true" tabindex="-1" href="#使用select"><span class="icon icon-link"></span></a>使用select</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line">fd_set read_fds<span class="token punctuation">;</span> <span class="token comment">// 定义文件描述符集合</span>
|
||
</span><span class="code-line"><span class="token function">FD_ZERO</span><span class="token punctuation">(</span><span class="token operator">&</span>read_fds<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 清空集合</span>
|
||
</span><span class="code-line"><span class="token function">FD_SET</span><span class="token punctuation">(</span>server_socket<span class="token punctuation">,</span> <span class="token operator">&</span>read_fds<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 将服务端套接字加入集合</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> max_fd <span class="token operator">=</span> server_socket<span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> activity <span class="token operator">=</span> <span class="token function">select</span><span class="token punctuation">(</span>max_fd <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token operator">&</span>read_fds<span class="token punctuation">,</span> <span class="token constant">NULL</span><span class="token punctuation">,</span> <span class="token constant">NULL</span><span class="token punctuation">,</span> <span class="token constant">NULL</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 等待事件发生</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span>activity <span class="token operator"><</span> <span class="token number">0</span> <span class="token operator">&&</span> errno <span class="token operator">!=</span> EINTR<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">perror</span><span class="token punctuation">(</span><span class="token string">"select error"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="使用poll"><a aria-hidden="true" tabindex="-1" href="#使用poll"><span class="icon icon-link"></span></a>使用poll</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">pollfd</span> fds<span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">;</span> <span class="token comment">// 定义文件描述符数组</span>
|
||
</span><span class="code-line">fds<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">.</span>fd <span class="token operator">=</span> server_socket<span class="token punctuation">;</span>
|
||
</span><span class="code-line">fds<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">.</span>events <span class="token operator">=</span> POLLIN<span class="token punctuation">;</span> <span class="token comment">// 监听读事件</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">int</span> poll_count <span class="token operator">=</span> <span class="token function">poll</span><span class="token punctuation">(</span>fds<span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 等待事件</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span>poll_count <span class="token operator"><</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">perror</span><span class="token punctuation">(</span><span class="token string">"poll error"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div><div class="wrap h3body-not-exist"><div class="wrap-header h3wrap"><h3 id="使用epoll"><a aria-hidden="true" tabindex="-1" href="#使用epoll"><span class="icon icon-link"></span></a>使用epoll</h3><div class="wrap-body">
|
||
<pre class="language-c"><code class="language-c code-highlight"><span class="code-line"><span class="token keyword">int</span> epoll_fd <span class="token operator">=</span> <span class="token function">epoll_create1</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 创建 epoll 文件描述符</span>
|
||
</span><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">epoll_event</span> event<span class="token punctuation">;</span>
|
||
</span><span class="code-line">event<span class="token punctuation">.</span>events <span class="token operator">=</span> EPOLLIN<span class="token punctuation">;</span>
|
||
</span><span class="code-line">event<span class="token punctuation">.</span>data<span class="token punctuation">.</span>fd <span class="token operator">=</span> server_socket<span class="token punctuation">;</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">epoll_ctl</span><span class="token punctuation">(</span>epoll_fd<span class="token punctuation">,</span> EPOLL_CTL_ADD<span class="token punctuation">,</span> server_socket<span class="token punctuation">,</span> <span class="token operator">&</span>event<span class="token punctuation">)</span> <span class="token operator">==</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token function">perror</span><span class="token punctuation">(</span><span class="token string">"epoll_ctl failed"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">struct</span> <span class="token class-name">epoll_event</span> events<span class="token punctuation">[</span><span class="token number">10</span><span class="token punctuation">]</span><span class="token punctuation">;</span> <span class="token comment">// 事件数组</span>
|
||
</span><span class="code-line"><span class="token keyword">int</span> event_count <span class="token operator">=</span> <span class="token function">epoll_wait</span><span class="token punctuation">(</span>epoll_fd<span class="token punctuation">,</span> events<span class="token punctuation">,</span> <span class="token number">10</span><span class="token punctuation">,</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 等待事件发生</span>
|
||
</span><span class="code-line">
|
||
</span><span class="code-line"><span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator"><</span> event_count<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token keyword">if</span> <span class="token punctuation">(</span>events<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">.</span>data<span class="token punctuation">.</span>fd <span class="token operator">==</span> server_socket<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
||
</span><span class="code-line"> <span class="token comment">// 处理服务端套接字上的事件</span>
|
||
</span><span class="code-line"> <span class="token punctuation">}</span>
|
||
</span><span class="code-line"><span class="token punctuation">}</span>
|
||
</span></code></pre>
|
||
</div></div></div></div></div><div class="wrap h2body-exist"><div class="wrap-header h2wrap"><h2 id="杂项"><a aria-hidden="true" tabindex="-1" href="#杂项"><span class="icon icon-link"></span></a>杂项</h2><div class="wrap-body">
|
||
</div></div><div class="h2wrap-body"><div class="wrap h3body-not-exist col-span-2"><div class="wrap-header h3wrap"><h3 id="docker-运行环境"><a aria-hidden="true" tabindex="-1" href="#docker-运行环境"><span class="icon icon-link"></span></a>Docker 运行环境</h3><div class="wrap-body">
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
<ul class="style-timeline">
|
||
<li>
|
||
<p>安装 <a href="./docker.html"><code>Docker</code></a></p>
|
||
</li>
|
||
<li>
|
||
<p>创建 <a href="./dockerfile.html"><code>Dockerfile</code></a> 文件</p>
|
||
<pre class="language-dockerfile"><code class="language-dockerfile code-highlight"><span class="code-line"><span class="token instruction"><span class="token keyword">FROM</span> alpine:3.14</span>
|
||
</span><span class="code-line"><span class="token instruction"><span class="token keyword">RUN</span> apk add --no-cache gcc musl-dev</span>
|
||
</span><span class="code-line"><span class="token instruction"><span class="token keyword">RUN</span> apk add --no-cache g++</span>
|
||
</span></code></pre>
|
||
</li>
|
||
<li>
|
||
<p>生成本地 myalpine 镜像</p>
|
||
<pre class="language-bash"><code class="language-bash code-highlight"><span class="code-line"><span class="token function">docker</span> build <span class="token parameter variable">-t</span> myalpine <span class="token builtin class-name">.</span>
|
||
</span></code></pre>
|
||
</li>
|
||
<li>
|
||
<p>运行映像，把当前路径 <code>($PWD)</code> 映射至容器的 <code>/test</code> 目录，用 <code>gcc</code> 编译程序，<code>exit</code>返回</p>
|
||
<pre class="language-bash"><code class="language-bash code-highlight"><span class="code-line"><span class="token function">docker</span> run <span class="token parameter variable">-it</span> <span class="token parameter variable">-v</span> <span class="token environment constant">$PWD</span>:/test myalpine
|
||
</span><span class="code-line">root@b1a38bd7107a:/<span class="token comment"># cd test</span>
|
||
</span><span class="code-line">root@b1a38bd7107a:/test<span class="token comment"># gcc -o hello hello.c</span>
|
||
</span><span class="code-line">Hello World
|
||
</span><span class="code-line">root@b1a38bd7107a:/test<span class="token comment"># exit</span>
|
||
</span><span class="code-line"><span class="token builtin class-name">exit</span>
|
||
</span></code></pre>
|
||
</li>
|
||
</ul>
|
||
<!--rehype:className=style-timeline-->
|
||
</div></div></div></div></div><div class="wrap h2body-not-exist"><div class="wrap-header h2wrap"><h2 id="另见"><a aria-hidden="true" tabindex="-1" href="#另见"><span class="icon icon-link"></span></a>另见</h2><div class="wrap-body">
|
||
<ul>
|
||
<li><a href="https://jaywcjlove.github.io/c-tutorial">C 教程</a> <em>(jaywcjlove.github.io)</em></li>
|
||
</ul>
|
||
</div></div><div class="h2wrap-body"></div></div></div><script src="https://giscus.app/client.js" data-repo="jaywcjlove/reference" data-repo-id="R_kgDOID2-Mw" data-category="Q&A" data-category-id="DIC_kwDOID2-M84CS5wo" data-mapping="pathname" data-strict="0" data-reactions-enabled="1" data-emit-metadata="0" data-input-position="bottom" data-theme="dark" data-lang="zh-CN" crossorigin="anonymous" async></script><div class="giscus"></div></div><footer class="footer-wrap"><footer class="max-container">© 2022 <a href="https://wangchujiang.com/#/app" target="_blank">Kenny Wang</a>.</footer></footer><script src="../data.js?v=1.8.1" defer></script><script src="../js/fuse.min.js?v=1.8.1" defer></script><script src="../js/main.js?v=1.8.1" defer></script><div id="mysearch"><div class="mysearch-box"><div class="mysearch-input"><div><svg xmlns="http://www.w3.org/2000/svg" height="1em" width="1em" viewBox="0 0 18 18">
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</svg><input id="mysearch-input" type="search" placeholder="搜索" autocomplete="off"><div class="mysearch-clear"></div></div><button id="mysearch-close" type="button">搜索</button></div><div class="mysearch-result"><div id="mysearch-menu"></div><div id="mysearch-content"></div></div></div></div></body>
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