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<ol class="chapter"><li class="chapter-item expanded affix "><a href="title-page.html">Rust 程序设计语言</a></li><li class="chapter-item expanded affix "><a href="foreword.html">前言</a></li><li class="chapter-item expanded affix "><a href="ch00-00-introduction.html">简介</a></li><li class="chapter-item expanded "><a href="ch01-00-getting-started.html"><strong aria-hidden="true">1.</strong> 入门指南</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch01-01-installation.html"><strong aria-hidden="true">1.1.</strong> 安装</a></li><li class="chapter-item expanded "><a href="ch01-02-hello-world.html" class="active"><strong aria-hidden="true">1.2.</strong> Hello, World!</a></li><li class="chapter-item expanded "><a href="ch01-03-hello-cargo.html"><strong aria-hidden="true">1.3.</strong> Hello, Cargo!</a></li></ol></li><li class="chapter-item expanded "><a href="ch02-00-guessing-game-tutorial.html"><strong aria-hidden="true">2.</strong> 写个猜数字游戏</a></li><li class="chapter-item expanded "><a href="ch03-00-common-programming-concepts.html"><strong aria-hidden="true">3.</strong> 常见编程概念</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch03-01-variables-and-mutability.html"><strong aria-hidden="true">3.1.</strong> 变量与可变性</a></li><li class="chapter-item expanded "><a href="ch03-02-data-types.html"><strong aria-hidden="true">3.2.</strong> 数据类型</a></li><li class="chapter-item expanded "><a href="ch03-03-how-functions-work.html"><strong aria-hidden="true">3.3.</strong> 函数</a></li><li class="chapter-item expanded "><a href="ch03-04-comments.html"><strong aria-hidden="true">3.4.</strong> 注释</a></li><li class="chapter-item expanded "><a href="ch03-05-control-flow.html"><strong aria-hidden="true">3.5.</strong> 控制流</a></li></ol></li><li class="chapter-item expanded "><a href="ch04-00-understanding-ownership.html"><strong aria-hidden="true">4.</strong> 认识所有权</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch04-01-what-is-ownership.html"><strong aria-hidden="true">4.1.</strong> 什么是所有权?</a></li><li class="chapter-item expanded "><a href="ch04-02-references-and-borrowing.html"><strong aria-hidden="true">4.2.</strong> 引用与借用</a></li><li class="chapter-item expanded "><a href="ch04-03-slices.html"><strong aria-hidden="true">4.3.</strong> Slice 类型</a></li></ol></li><li class="chapter-item expanded "><a href="ch05-00-structs.html"><strong aria-hidden="true">5.</strong> 使用结构体组织相关联的数据</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch05-01-defining-structs.html"><strong aria-hidden="true">5.1.</strong> 结构体的定义和实例化</a></li><li class="chapter-item expanded "><a href="ch05-02-example-structs.html"><strong aria-hidden="true">5.2.</strong> 结构体示例程序</a></li><li class="chapter-item expanded "><a href="ch05-03-method-syntax.html"><strong aria-hidden="true">5.3.</strong> 方法语法</a></li></ol></li><li class="chapter-item expanded "><a href="ch06-00-enums.html"><strong aria-hidden="true">6.</strong> 枚举和模式匹配</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch06-01-defining-an-enum.html"><strong aria-hidden="true">6.1.</strong> 枚举的定义</a></li><li class="chapter-item expanded "><a href="ch06-02-match.html"><strong aria-hidden="true">6.2.</strong> match 控制流结构</a></li><li class="chapter-item expanded "><a href="ch06-03-if-let.html"><strong aria-hidden="true">6.3.</strong> if let 简洁控制流</a></li></ol></li><li class="chapter-item expanded "><a href="ch07-00-managing-growing-projects-with-packages-crates-and-modules.html"><strong aria-hidden="true">7.</strong> 使用包、Crate 和模块管理不断增长的项目</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch07-01-packages-and-crates.html"><strong aria-hidden="true">7.1.</strong> 包和 Crate</a></li><li class="chapter-item expanded "><a href="ch07-02-defining-modules-to-control-scope-and-privacy.html"><strong aria-hidden="true">7.2.</strong> 定义模块来控制作用域与私有性</a></li><li class="chapter-item expanded "><a href="ch07-03-paths-for-referring-to-an-item-in-the-module-tree.html"><strong aria-hidden="true">7.3.</strong> 引用模块项目的路径</a></li><li class="chapter-item expanded "><a href="ch07-04-bringing-paths-into-scope-with-the-use-keyword.html"><strong aria-hidden="true">7.4.</strong> 使用 use 关键字将路径引入作用域</a></li><li class="chapter-item expanded "><a href="ch07-05-separating-modules-into-different-files.html"><strong aria-hidden="true">7.5.</strong> 将模块拆分成多个文件</a></li></ol></li><li class="chapter-item expanded "><a href="ch08-00-common-collections.html"><strong aria-hidden="true">8.</strong> 常见集合</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch08-01-vectors.html"><strong aria-hidden="true">8.1.</strong> 使用 Vector 储存列表</a></li><li class="chapter-item expanded "><a href="ch08-02-strings.html"><strong aria-hidden="true">8.2.</strong> 使用字符串储存 UTF-8 编码的文本</a></li><li class="chapter-item expanded "><a href="ch08-03-hash-maps.html"><strong aria-hidden="true">8.3.</strong> 使用 Hash Map 储存键值对</a></li></ol></li><li class="chapter-item expanded "><a href="ch09-00-error-handling.html"><strong aria-hidden="true">9.</strong> 错误处理</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch09-01-unrecoverable-errors-with-panic.html"><strong aria-hidden="true">9.1.</strong> 用 panic! 处理不可恢复的错误</a></li><li class="chapter-item expanded "><a href="ch09-02-recoverable-errors-with-result.html"><strong aria-hidden="true">9.2.</strong> 用 Result 处理可恢复的错误</a></li><li class="chapter-item expanded "><a href="ch09-03-to-panic-or-not-to-panic.html"><strong aria-hidden="true">9.3.</strong> 要不要 panic!</a></li></ol></li><li class="chapter-item expanded "><a href="ch10-00-generics.html"><strong aria-hidden="true">10.</strong> 泛型、Trait 和生命周期</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch10-01-syntax.html"><strong aria-hidden="true">10.1.</strong> 泛型数据类型</a></li><li class="chapter-item expanded "><a href="ch10-02-traits.html"><strong aria-hidden="true">10.2.</strong> Trait定义共同行为</a></li><li class="chapter-item expanded "><a href="ch10-03-lifetime-syntax.html"><strong aria-hidden="true">10.3.</strong> 生命周期确保引用有效</a></li></ol></li><li class="chapter-item expanded "><a href="ch11-00-testing.html"><strong aria-hidden="true">11.</strong> 编写自动化测试</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch11-01-writing-tests.html"><strong aria-hidden="true">11.1.</strong> 如何编写测试</a></li><li class="chapter-item expanded "><a href="ch11-02-running-tests.html"><strong aria-hidden="true">11.2.</strong> 控制测试如何运行</a></li><li class="chapter-item expanded "><a href="ch11-03-test-organization.html"><strong aria-hidden="true">11.3.</strong> 测试的组织结构</a></li></ol></li><li class="chapter-item expanded "><a href="ch12-00-an-io-project.html"><strong aria-hidden="true">12.</strong> 一个 I/O 项目:构建命令行程序</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch12-01-accepting-command-line-arguments.html"><strong aria-hidden="true">12.1.</strong> 接受命令行参数</a></li><li class="chapter-item expanded "><a href="ch12-02-reading-a-file.html"><strong aria-hidden="true">12.2.</strong> 读取文件</a></li><li class="chapter-item expanded "><a href="ch12-03-improving-error-handling-and-modularity.html"><strong aria-hidden="true">12.3.</strong> 重构以改进模块化与错误处理</a></li><li class="chapter-item expanded "><a href="ch12-04-testing-the-librarys-functionality.html"><strong aria-hidden="true">12.4.</strong> 采用测试驱动开发完善库的功能</a></li><li class="chapter-item expanded "><a href="ch12-05-working-with-environment-variables.html"><strong aria-hidden="true">12.5.</strong> 处理环境变量</a></li><li class="chapter-item expanded "><a href="ch12-06-writing-to-stderr-instead-of-stdout.html"><strong aria-hidden="true">12.6.</strong> 将错误信息输出到标准错误而不是标准输出</a></li></ol></li><li class="chapter-item expanded "><a href="ch13-00-functional-features.html"><strong aria-hidden="true">13.</strong> Rust 中的函数式语言功能:迭代器与闭包</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch13-01-closures.html"><strong aria-hidden="true">13.1.</strong> 闭包:可以捕获其环境的匿名函数</a></li><li class="chapter-item expanded "><a href="ch13-02-iterators.html"><strong aria-hidden="true">13.2.</strong> 使用迭代器处理元素序列</a></li><li class="chapter-item expanded "><a href="ch13-03-improving-our-io-project.html"><strong aria-hidden="true">13.3.</strong> 改进之前的 I/O 项目</a></li><li class="chapter-item expanded "><a href="ch13-04-performance.html"><strong aria-hidden="true">13.4.</strong> 性能比较:循环对迭代器</a></li></ol></li><li class="chapter-item expanded "><a href="ch14-00-more-about-cargo.html"><strong aria-hidden="true">14.</strong> 更多关于 Cargo 和 Crates.io 的内容</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch14-01-release-profiles.html"><strong aria-hidden="true">14.1.</strong> 采用发布配置自定义构建</a></li><li class="chapter-item expanded "><a href="ch14-02-publishing-to-crates-io.html"><strong aria-hidden="true">14.2.</strong> 将 crate 发布到 Crates.io</a></li><li class="chapter-item expanded "><a href="ch14-03-cargo-workspaces.html"><strong aria-hidden="true">14.3.</strong> Cargo 工作空间</a></li><li class="chapter-item expanded "><a href="ch14-04-installing-binaries.html"><strong aria-hidden="true">14.4.</strong> 使用 cargo install 安装二进制文件</a></li><li class="chapter-item expanded "><a href="ch14-05-extending-cargo.html"><strong aria-hidden="true">14.5.</strong> Cargo 自定义扩展命令</a></li></ol></li><li class="chapter-item expanded "><a href="ch15-00-smart-pointers.html"><strong aria-hidden="true">15.</strong> 智能指针</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch15-01-box.html"><strong aria-hidden="true">15.1.</strong> 使用 Box&lt;T&gt; 指向堆上数据</a></li><li class="chapter-item expanded "><a href="ch15-02-deref.html"><strong aria-hidden="true">15.2.</strong> 使用 Deref Trait 将智能指针当作常规引用处理</a></li><li class="chapter-item expanded "><a href="ch15-03-drop.html"><strong aria-hidden="true">15.3.</strong> 使用 Drop Trait 运行清理代码</a></li><li class="chapter-item expanded "><a href="ch15-04-rc.html"><strong aria-hidden="true">15.4.</strong> Rc&lt;T&gt; 引用计数智能指针</a></li><li class="chapter-item expanded "><a href="ch15-05-interior-mutability.html"><strong aria-hidden="true">15.5.</strong> RefCell&lt;T&gt; 与内部可变性模式</a></li><li class="chapter-item expanded "><a href="ch15-06-reference-cycles.html"><strong aria-hidden="true">15.6.</strong> 引用循环会导致内存泄漏</a></li></ol></li><li class="chapter-item expanded "><a href="ch16-00-concurrency.html"><strong aria-hidden="true">16.</strong> 无畏并发</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch16-01-threads.html"><strong aria-hidden="true">16.1.</strong> 使用线程同时地运行代码</a></li><li class="chapter-item expanded "><a href="ch16-02-message-passing.html"><strong aria-hidden="true">16.2.</strong> 使用消息传递在线程间通信</a></li><li class="chapter-item expanded "><a href="ch16-03-shared-state.html"><strong aria-hidden="true">16.3.</strong> 共享状态并发</a></li><li class="chapter-item expanded "><a href="ch16-04-extensible-concurrency-sync-and-send.html"><strong aria-hidden="true">16.4.</strong> 使用 Sync 与 Send Traits 的可扩展并发</a></li></ol></li><li class="chapter-item expanded "><a href="ch17-00-async-await.html"><strong aria-hidden="true">17.</strong> Async 和 await</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch17-01-futures-and-syntax.html"><strong aria-hidden="true">17.1.</strong> Futures 和 async 语法</a></li><li class="chapter-item expanded "><a href="ch17-02-concurrency-with-async.html"><strong aria-hidden="true">17.2.</strong> 并发与 async</a></li><li class="chapter-item expanded "><a href="ch17-03-more-futures.html"><strong aria-hidden="true">17.3.</strong> 使用任意数量的 futures</a></li><li class="chapter-item expanded "><a href="ch17-04-streams.html"><strong aria-hidden="true">17.4.</strong>Streams</a></li><li class="chapter-item expanded "><a href="ch17-05-traits-for-async.html"><strong aria-hidden="true">17.5.</strong> 深入理解 async 相关的 traits</a></li><li class="chapter-item expanded "><a href="ch17-06-futures-tasks-threads.html"><strong aria-hidden="true">17.6.</strong> Futures任务tasks和线程threads</a></li></ol></li><li class="chapter-item expanded "><a href="ch18-00-oop.html"><strong aria-hidden="true">18.</strong> Rust 的面向对象编程特性</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch18-01-what-is-oo.html"><strong aria-hidden="true">18.1.</strong> 面向对象语言的特点</a></li><li class="chapter-item expanded "><a href="ch18-02-trait-objects.html"><strong aria-hidden="true">18.2.</strong> 顾及不同类型值的 trait 对象</a></li><li class="chapter-item expanded "><a href="ch18-03-oo-design-patterns.html"><strong aria-hidden="true">18.3.</strong> 面向对象设计模式的实现</a></li></ol></li><li class="chapter-item expanded "><a href="ch19-00-patterns.html"><strong aria-hidden="true">19.</strong> 模式与模式匹配</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch19-01-all-the-places-for-patterns.html"><strong aria-hidden="true">19.1.</strong> 所有可能会用到模式的位置</a></li><li class="chapter-item expanded "><a href="ch19-02-refutability.html"><strong aria-hidden="true">19.2.</strong> Refutability可反驳性: 模式是否会匹配失效</a></li><li class="chapter-item expanded "><a href="ch19-03-pattern-syntax.html"><strong aria-hidden="true">19.3.</strong> 模式语法</a></li></ol></li><li class="chapter-item expanded "><a href="ch20-00-advanced-features.html"><strong aria-hidden="true">20.</strong> 高级特征</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch20-01-unsafe-rust.html"><strong aria-hidden="true">20.1.</strong> 不安全的 Rust</a></li><li class="chapter-item expanded "><a href="ch20-03-advanced-traits.html"><strong aria-hidden="true">20.2.</strong> 高级 trait</a></li><li class="chapter-item expanded "><a href="ch20-04-advanced-types.html"><strong aria-hidden="true">20.3.</strong> 高级类型</a></li><li class="chapter-item expanded "><a href="ch20-05-advanced-functions-and-closures.html"><strong aria-hidden="true">20.4.</strong> 高级函数与闭包</a></li><li class="chapter-item expanded "><a href="ch20-06-macros.html"><strong aria-hidden="true">20.5.</strong></a></li></ol></li><li class="chapter-item expanded "><a href="ch21-00-final-project-a-web-server.html"><strong aria-hidden="true">21.</strong> 最后的项目:构建多线程 web server</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch21-01-single-threaded.html"><strong aria-hidden="true">21.1.</strong> 建立单线程 web server</a></li><li class="chapter-item expanded "><a href="ch21-02-multithreaded.html"><strong aria-hidden="true">21.2.</strong> 将单线程 server 变为多线程 server</a></li><li class="chapter-item expanded "><a href="ch21-03-graceful-shutdown-and-cleanup.html"><strong aria-hidden="true">21.3.</strong> 优雅停机与清理</a></li></ol></li><li class="chapter-item expanded "><a href="appendix-00.html"><strong aria-hidden="true">22.</strong> 附录</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="appendix-01-keywords.html"><strong aria-hidden="true">22.1.</strong> A - 关键字</a></li><li class="chapter-item expanded "><a href="appendix-02-operators.html"><strong aria-hidden="true">22.2.</strong> B - 运算符与符号</a></li><li class="chapter-item expanded "><a href="appendix-03-derivable-traits.html"><strong aria-hidden="true">22.3.</strong> C - 可派生的 trait</a></li><li class="chapter-item expanded "><a href="appendix-04-useful-development-tools.html"><strong aria-hidden="true">22.4.</strong> D - 实用开发工具</a></li><li class="chapter-item expanded "><a href="appendix-05-editions.html"><strong aria-hidden="true">22.5.</strong> E - 版本</a></li><li class="chapter-item expanded "><a href="appendix-06-translation.html"><strong aria-hidden="true">22.6.</strong> F - 本书译本</a></li><li class="chapter-item expanded "><a href="appendix-07-nightly-rust.html"><strong aria-hidden="true">22.7.</strong> G - Rust 是如何开发的与 “Nightly Rust”</a></li></ol></li></ol>
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<h2 id="hello-world"><a class="header" href="#hello-world">Hello, World!</a></h2>
<blockquote>
<p><a href="https://github.com/rust-lang/book/blob/main/src/ch01-02-hello-world.md">ch01-02-hello-world.md</a>
<br>
commit 1fb74c3f1d8aeba39373e9f4cdb9a4bdca95604f</p>
</blockquote>
<p>既然安装好了 Rust是时候来编写第一个 Rust 程序了。当学习一门新语言的时候,使用该语言在屏幕上打印 <code>Hello, world!</code> 是一项传统,我们将沿用这一传统!</p>
<blockquote>
<p>注意本书假设你熟悉基本的命令行操作。Rust 对于你的编辑器、工具以及代码位于何处并没有特定的要求如果你更倾向于使用集成开发环境IDE而不是命令行请尽管使用你喜欢的 IDE。目前很多 IDE 都在一定程度上支持 Rust查看 IDE 文档以了解更多细节。Rust 团队一直致力于借助 <code>rust-analyzer</code> 提供强大的 IDE 支持。详见<a href="appendix-04-useful-development-tools.html">附录 D</a><!-- ignore --></p>
</blockquote>
<h3 id="创建项目目录"><a class="header" href="#创建项目目录">创建项目目录</a></h3>
<p>首先创建一个存放 Rust 代码的目录。Rust 并不关心代码的存放位置,不过对于本书的练习和项目来说,我们建议你在 home 目录中创建 <em>projects</em> 目录,并将你的所有项目存放在这里。</p>
<p>打开终端并输入如下命令创建 <em>projects</em> 目录,并在 <em>projects</em> 目录中为 “Hello, world!” 项目创建一个目录。</p>
<p>对于 Linux、macOS 和 Windows PowerShell输入</p>
<pre><code class="language-console">$ mkdir ~/projects
$ cd ~/projects
$ mkdir hello_world
$ cd hello_world
</code></pre>
<p>对于 Windows CMD输入</p>
<pre><code class="language-doscon">&gt; mkdir "%USERPROFILE%\projects"
&gt; cd /d "%USERPROFILE%\projects"
&gt; mkdir hello_world
&gt; cd hello_world
</code></pre>
<h3 id="编写并运行-rust-程序"><a class="header" href="#编写并运行-rust-程序">编写并运行 Rust 程序</a></h3>
<p>接下来,新建一个源文件,命名为 <em>main.rs</em>。Rust 源文件总是以 <em>.rs</em> 扩展名结尾。如果文件名包含多个单词,那么按照命名习惯,应当使用下划线来分隔单词。例如命名为 <em>hello_world.rs</em>,而不是 <em>helloworld.rs</em></p>
<p>现在打开刚创建的 <em>main.rs</em> 文件,输入示例 1-1 中的代码。</p>
<figure class="listing">
<p><span class="file-name">文件名main.rs</span></p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
println!("Hello, world!");
}</code></pre></pre>
<figcaption>示例 1-1一个打印 `Hello, world!` 的程序</figcaption>
</figure>
<p>保存文件,并回到当前目录为“~/projects/hello_world”的终端窗口。在 Linux 或 macOS 上,输入如下命令,编译并运行文件:</p>
<pre><code class="language-console">$ rustc main.rs
$ ./main
Hello, world!
</code></pre>
<p>在 Windows 上,输入命令 <code>.\main.exe</code>,而不是 <code>./main</code></p>
<pre><code class="language-powershell">&gt; rustc main.rs
&gt; .\main.exe
Hello, world!
</code></pre>
<p>不管使用何种操作系统,终端应该打印字符串 <code>Hello, world!</code>。如果没有看到这些输出,回到安装部分的 <a href="ch01-01-installation.html#%E6%95%85%E9%9A%9C%E6%8E%92%E9%99%A4troubleshooting">“故障排除”</a> 小节查找有帮助的方法。</p>
<p>如果 <code>Hello, world!</code> 出现了,恭喜你!你已经正式编写了一个 Rust 程序。现在你成为一名 Rust 程序员,欢迎!</p>
<h3 id="分析这个-rust-程序"><a class="header" href="#分析这个-rust-程序">分析这个 Rust 程序</a></h3>
<p>现在,让我们回过头来仔细看看这个 “Hello, world!” 程序。这是第一块拼图:</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
}</code></pre></pre>
<p>这几行定义了一个名叫 <code>main</code> 的函数。<code>main</code> 函数是一个特殊的函数:在可执行的 Rust 程序中,它总是最先运行的代码。第一行代码声明了一个叫做 <code>main</code> 的函数,它没有参数也没有返回值。如果有参数的话,它们的名称应该出现在小括号 <code>()</code> 中。</p>
<p>函数体被包裹在 <code>{}</code> 中。Rust 要求所有函数体都要用花括号包裹起来。一般来说,将左花括号与函数声明置于同一行并以空格分隔,是良好的代码风格。</p>
<blockquote>
<p>注:如果你希望在 Rust 项目中保持一种标准风格,可以使用名为 <code>rustfmt</code> 的自动格式化工具将代码格式化为特定的风格(更多内容详见<a href="appendix-04-useful-development-tools.html">附录 D</a> 中的 <code>rustfmt</code><!-- ignore -->。Rust 团队已经在标准的 Rust 发行版中包含了这个工具,就像 <code>rustc</code> 一样。所以它应该已经安装在你的电脑中了!</p>
</blockquote>
<p><code>main</code> 函数中有如下代码:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span> println!("Hello, world!");
<span class="boring">}</span></code></pre></pre>
<p>这行代码完成这个简单程序的所有工作:在屏幕上打印文本。这里有四个重要的细节需要注意。首先 Rust 的缩进风格使用 4 个空格,而不是 1 个制表符tab</p>
<p>第二,<code>println!</code> 调用了一个 Rust 宏macro。如果是调用函数则应输入 <code>println</code>(没有<code>!</code>)。我们将在第二十章详细讨论宏。现在你只需记住,当看到符号 <code>!</code> 的时候,就意味着调用的是宏而不是普通函数,并且宏并不总是遵循与函数相同的规则。</p>
<p>第三,<code>"Hello, world!"</code> 是一个字符串。我们把这个字符串作为一个参数传递给 <code>println!</code>,字符串将被打印到屏幕上。</p>
<p>第四,该行以分号结尾(<code>;</code>),这代表一个表达式的结束和下一个表达式的开始。大部分 Rust 代码行以分号结尾。</p>
<h3 id="编译和运行是彼此独立的步骤"><a class="header" href="#编译和运行是彼此独立的步骤">编译和运行是彼此独立的步骤</a></h3>
<p>你刚刚运行了一个新创建的程序,那么让我们检查此过程中的每一个步骤。</p>
<p>在运行 Rust 程序之前,必须先使用 Rust 编译器编译它,即输入 <code>rustc</code> 命令并传入源文件名称,如下:</p>
<pre><code class="language-console">$ rustc main.rs
</code></pre>
<p>如果你有 C 或 C++ 背景,就会发现这与 <code>gcc</code><code>clang</code> 类似。编译成功后Rust 会输出一个二进制的可执行文件。</p>
<p>在 Linux、macOS 或 Windows 的 PowerShell 上,在 shell 中输入 <code>ls</code> 命令可以看见这个可执行文件。</p>
<pre><code class="language-console">$ ls
main main.rs
</code></pre>
<p>在 Linux 和 macOS你会看到两个文件。在 Windows PowerShell 中,你会看到同使用 CMD 相同的三个文件。在 Windows 的 CMD 上,则输入如下内容:</p>
<pre><code class="language-doscon">&gt; dir /B %= the /B option says to only show the file names =%
main.exe
main.pdb
main.rs
</code></pre>
<p>这展示了扩展名为 <em>.rs</em> 的源文件、可执行文件(在 Windows 下是 <em>main.exe</em>,其它平台是 <em>main</em>),以及当使用 CMD 时会有一个包含调试信息、扩展名为 <em>.pdb</em> 的文件。从这里开始运行 <em>main</em><em>main.exe</em> 文件,如下:</p>
<pre><code class="language-console">$ ./main # Windows 是 .\main.exe
</code></pre>
<p>如果这里的 <em>main.rs</em> 是上文所述的 “Hello, world!” 程序,那么在终端上就会打印出 <code>Hello, world!</code></p>
<p>如果你更熟悉动态语言,如 Ruby、Python 或 JavaScript则可能不习惯将编译和运行分为两个单独的步骤。Rust 是一种 <strong>预编译静态类型</strong><em>ahead-of-time compiled</em>)语言,这意味着你可以编译程序,并将可执行文件送给其他人,他们甚至不需要安装 Rust 就可以运行。如果你给他人一个 <em>.rb</em><em>.py</em><em>.js</em> 文件,他们需要先分别安装 RubyPythonJavaScript 实现运行时环境VM。不过在这些语言中只需要一句命令就可以编译和运行程序。这一切都是语言设计上的权衡取舍。</p>
<p>仅仅使用 <code>rustc</code> 编译简单程序是没问题的,不过随着项目的增长,你可能需要管理你项目的方方面面,并让代码易于分享。接下来,我们要介绍一个叫做 Cargo 的工具,它会帮助你编写真实世界中的 Rust 程序。</p>
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