<!DOCTYPE HTML> <html lang="en" class="sidebar-visible no-js"> <head> <!-- Book generated using mdBook --> <meta charset="UTF-8"> <title>Dependencies - The Cargo Book</title> <meta content="text/html; charset=utf-8" http-equiv="Content-Type"> <meta name="description" content=""> <meta name="viewport" content="width=device-width, initial-scale=1"> <meta name="theme-color" content="#ffffff" /> <base href="../"> <link rel="stylesheet" href="book.css"> <link href="https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,800italic,400,300,600,700,800" rel="stylesheet" type="text/css"> <link href="https://fonts.googleapis.com/css?family=Source+Code+Pro:500" rel="stylesheet" type="text/css"> <link rel="shortcut icon" href="favicon.png"> <!-- Font Awesome --> <link rel="stylesheet" href="_FontAwesome/css/font-awesome.css"> <link rel="stylesheet" href="highlight.css"> <link rel="stylesheet" href="tomorrow-night.css"> <link rel="stylesheet" href="ayu-highlight.css"> <!-- Custom theme stylesheets --> </head> <body class="light"> <!-- Work around some values being stored in localStorage wrapped in quotes --> <script type="text/javascript"> try { var theme = localStorage.getItem('mdbook-theme'); 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html.classList.add("sidebar-" + sidebar); </script> <nav id="sidebar" class="sidebar" aria-label="Table of contents"> <ol class="chapter"><li class="affix"><a href="index.html">Introduction</a></li><li><a href="getting-started/index.html"><strong aria-hidden="true">1.</strong> Getting Started</a></li><li><ol class="section"><li><a href="getting-started/installation.html"><strong aria-hidden="true">1.1.</strong> Installation</a></li><li><a href="getting-started/first-steps.html"><strong aria-hidden="true">1.2.</strong> First Steps with Cargo</a></li></ol></li><li><a href="guide/index.html"><strong aria-hidden="true">2.</strong> Cargo Guide</a></li><li><ol class="section"><li><a href="guide/why-cargo-exists.html"><strong aria-hidden="true">2.1.</strong> Why Cargo Exists</a></li><li><a href="guide/creating-a-new-project.html"><strong aria-hidden="true">2.2.</strong> Creating a New Project</a></li><li><a href="guide/working-on-an-existing-project.html"><strong aria-hidden="true">2.3.</strong> Working on an Existing Project</a></li><li><a href="guide/dependencies.html" class="active"><strong aria-hidden="true">2.4.</strong> Dependencies</a></li><li><a href="guide/project-layout.html"><strong aria-hidden="true">2.5.</strong> Project Layout</a></li><li><a href="guide/cargo-toml-vs-cargo-lock.html"><strong aria-hidden="true">2.6.</strong> Cargo.toml vs Cargo.lock</a></li><li><a href="guide/tests.html"><strong aria-hidden="true">2.7.</strong> Tests</a></li><li><a href="guide/continuous-integration.html"><strong aria-hidden="true">2.8.</strong> Continuous Integration</a></li><li><a href="guide/build-cache.html"><strong aria-hidden="true">2.9.</strong> Build Cache</a></li></ol></li><li><a href="reference/index.html"><strong aria-hidden="true">3.</strong> Cargo Reference</a></li><li><ol class="section"><li><a href="reference/specifying-dependencies.html"><strong aria-hidden="true">3.1.</strong> Specifying Dependencies</a></li><li><a href="reference/manifest.html"><strong aria-hidden="true">3.2.</strong> The Manifest Format</a></li><li><a href="reference/config.html"><strong aria-hidden="true">3.3.</strong> Configuration</a></li><li><a href="reference/environment-variables.html"><strong aria-hidden="true">3.4.</strong> Environment Variables</a></li><li><a href="reference/build-scripts.html"><strong aria-hidden="true">3.5.</strong> Build Scripts</a></li><li><a href="reference/publishing.html"><strong aria-hidden="true">3.6.</strong> Publishing on crates.io</a></li><li><a href="reference/pkgid-spec.html"><strong aria-hidden="true">3.7.</strong> Package ID Specifications</a></li><li><a href="reference/source-replacement.html"><strong aria-hidden="true">3.8.</strong> Source Replacement</a></li><li><a href="reference/external-tools.html"><strong aria-hidden="true">3.9.</strong> External Tools</a></li><li><a href="reference/unstable.html"><strong aria-hidden="true">3.10.</strong> Unstable Features</a></li></ol></li><li><a href="faq.html"><strong aria-hidden="true">4.</strong> FAQ</a></li></ol> </nav> <div id="page-wrapper" class="page-wrapper"> <div class="page"> <div id="menu-bar" class="menu-bar"> <div id="menu-bar-sticky-container"> <div class="left-buttons"> <button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar"> <i class="fa fa-bars"></i> </button> <button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list"> <i class="fa fa-paint-brush"></i> </button> <ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu"> <li role="none"><button role="menuitem" class="theme" id="light">Light <span class="default">(default)</span></button></li> <li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li> <li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li> <li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li> <li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li> </ul> <button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar"> <i class="fa fa-search"></i> </button> </div> <h1 class="menu-title">The Cargo Book</h1> <div class="right-buttons"> <a href="print.html" title="Print this book" aria-label="Print this book"> <i id="print-button" class="fa fa-print"></i> </a> </div> </div> </div> <div id="search-wrapper" class="hidden"> <form id="searchbar-outer" class="searchbar-outer"> <input type="search" name="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header"> </form> <div id="searchresults-outer" class="searchresults-outer hidden"> <div id="searchresults-header" class="searchresults-header"></div> <ul id="searchresults"> </ul> </div> </div> <!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM --> <script type="text/javascript"> document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible'); document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible'); Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) { link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1); }); </script> <div id="content" class="content"> <main> <a class="header" href="guide/dependencies.html#dependencies" id="dependencies"><h2>Dependencies</h2></a> <p><a href="https://crates.io/">crates.io</a> is the Rust community's central package registry that serves as a location to discover and download packages. <code>cargo</code> is configured to use it by default to find requested packages.</p> <p>To depend on a library hosted on <a href="https://crates.io/">crates.io</a>, add it to your <code>Cargo.toml</code>.</p> <a class="header" href="guide/dependencies.html#adding-a-dependency" id="adding-a-dependency"><h3>Adding a dependency</h3></a> <p>If your <code>Cargo.toml</code> doesn't already have a <code>[dependencies]</code> section, add that, then list the crate name and version that you would like to use. This example adds a dependency of the <code>time</code> crate:</p> <pre><code class="language-toml">[dependencies] time = "0.1.12" </code></pre> <p>The version string is a <a href="https://github.com/steveklabnik/semver#requirements">semver</a> version requirement. The <a href="reference/specifying-dependencies.html">specifying dependencies</a> docs have more information about the options you have here.</p> <p>If we also wanted to add a dependency on the <code>regex</code> crate, we would not need to add <code>[dependencies]</code> for each crate listed. Here's what your whole <code>Cargo.toml</code> file would look like with dependencies on the <code>time</code> and <code>regex</code> crates:</p> <pre><code class="language-toml">[package] name = "hello_world" version = "0.1.0" authors = ["Your Name <you@example.com>"] [dependencies] time = "0.1.12" regex = "0.1.41" </code></pre> <p>Re-run <code>cargo build</code>, and Cargo will fetch the new dependencies and all of their dependencies, compile them all, and update the <code>Cargo.lock</code>:</p> <pre><code class="language-console">$ cargo build Updating registry `https://github.com/rust-lang/crates.io-index` Downloading memchr v0.1.5 Downloading libc v0.1.10 Downloading regex-syntax v0.2.1 Downloading memchr v0.1.5 Downloading aho-corasick v0.3.0 Downloading regex v0.1.41 Compiling memchr v0.1.5 Compiling libc v0.1.10 Compiling regex-syntax v0.2.1 Compiling memchr v0.1.5 Compiling aho-corasick v0.3.0 Compiling regex v0.1.41 Compiling hello_world v0.1.0 (file:///path/to/project/hello_world) </code></pre> <p>Our <code>Cargo.lock</code> contains the exact information about which revision of all of these dependencies we used.</p> <p>Now, if <code>regex</code> gets updated, we will still build with the same revision until we choose to <code>cargo update</code>.</p> <p>You can now use the <code>regex</code> library using <code>extern crate</code> in <code>main.rs</code>.</p> <pre><pre class="playpen"><code class="language-rust">extern crate regex; use regex::Regex; fn main() { let re = Regex::new(r"^\d{4}-\d{2}-\d{2}$").unwrap(); println!("Did our date match? {}", re.is_match("2014-01-01")); } </code></pre></pre> <p>Running it will show:</p> <pre><code class="language-console">$ cargo run Running `target/hello_world` Did our date match? true </code></pre> </main> <nav class="nav-wrapper" aria-label="Page navigation"> <!-- Mobile navigation buttons --> <a rel="prev" href="guide/working-on-an-existing-project.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> <i class="fa fa-angle-left"></i> </a> <a rel="next" href="guide/project-layout.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> <i class="fa fa-angle-right"></i> </a> <div style="clear: both"></div> </nav> </div> </div> <nav class="nav-wide-wrapper" aria-label="Page navigation"> <a href="guide/working-on-an-existing-project.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> <i class="fa fa-angle-left"></i> </a> <a href="guide/project-layout.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> <i class="fa fa-angle-right"></i> </a> </nav> </div> <script src="searchindex.js" type="text/javascript" charset="utf-8"></script> <script src="elasticlunr.min.js" type="text/javascript" charset="utf-8"></script> <script src="mark.min.js" type="text/javascript" charset="utf-8"></script> <script src="searcher.js" type="text/javascript" charset="utf-8"></script> <script src="clipboard.min.js" type="text/javascript" charset="utf-8"></script> <script src="highlight.js" type="text/javascript" charset="utf-8"></script> <script src="book.js" type="text/javascript" charset="utf-8"></script> <!-- Custom JS scripts --> </body> </html>