<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta name="generator" content="rustdoc"> <meta name="description" content="API documentation for the Rust `format` macro in crate `std`."> <meta name="keywords" content="rust, rustlang, rust-lang, format"> <title>std::format - Rust</title> <link rel="stylesheet" type="text/css" href="../normalize.css"> <link rel="stylesheet" type="text/css" href="../rustdoc.css"> <link rel="stylesheet" type="text/css" href="../main.css"> <link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"> </head> <body class="rustdoc macro"> <!--[if lte IE 8]> <div class="warning"> This old browser is unsupported and will most likely display funky things. </div> <![endif]--> <nav class="sidebar"> <a href='../std/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a> <p class='location'><a href='index.html'>std</a></p><script>window.sidebarCurrent = {name: 'format', ty: 'macro', relpath: ''};</script><script defer src="sidebar-items.js"></script> </nav> <nav class="sub"> <form class="search-form js-only"> <div class="search-container"> <input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"> </div> </form> </nav> <section id='main' class="content"> <h1 class='fqn'><span class='in-band'>Macro <a href='index.html'>std</a>::<wbr><a class="macro" href=''>format</a></span><span class='out-of-band'><span id='render-detail'> <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs"> [<span class='inner'>−</span>] </a> </span></span></h1> <pre class="rust macro"> <span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">format</span> { ( $ ( $ <span class="ident">arg</span> : <span class="ident">tt</span> ) <span class="op">*</span> ) <span class="op">=></span> { ... }; }</pre> <div class='docblock'><p>Use the syntax described in <code>std::fmt</code> to create a value of type <code>String</code>. See <a href="../std/fmt/index.html"><code>std::fmt</code></a> for more information.</p> <h1 id='panics' class='section-header'><a href='#panics'>Panics</a></h1> <p><code>format!</code> panics if a formatting trait implementation returns an error. This indicates an incorrect implementation since <code>fmt::Write for String</code> never returns an error itself.</p> <h1 id='examples' class='section-header'><a href='#examples'>Examples</a></h1> <pre class="rust rust-example-rendered"> <span class="macro">format</span><span class="macro">!</span>(<span class="string">"test"</span>); <span class="macro">format</span><span class="macro">!</span>(<span class="string">"hello {}"</span>, <span class="string">"world!"</span>); <span class="macro">format</span><span class="macro">!</span>(<span class="string">"x = {}, y = {y}"</span>, <span class="number">10</span>, <span class="ident">y</span> <span class="op">=</span> <span class="number">30</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Aformat!(%22test%22)%3B%0Aformat!(%22hello%20%7B%7D%22%2C%20%22world!%22)%3B%0Aformat!(%22x%20%3D%20%7B%7D%2C%20y%20%3D%20%7By%7D%22%2C%2010%2C%20y%20%3D%2030)%3B%0A%7D">Run</a></pre> </div></section> <section id='search' class="content hidden"></section> <section class="footer"></section> <aside id="help" class="hidden"> <div> <h1 class="hidden">Help</h1> <div class="shortcuts"> <h2>Keyboard Shortcuts</h2> <dl> <dt>?</dt> <dd>Show this help dialog</dd> <dt>S</dt> <dd>Focus the search field</dd> <dt>⇤</dt> <dd>Move up in search results</dd> <dt>⇥</dt> <dd>Move down in search results</dd> <dt>⏎</dt> <dd>Go to active search result</dd> <dt>+</dt> <dd>Collapse/expand all sections</dd> </dl> </div> <div class="infos"> <h2>Search Tricks</h2> <p> Prefix searches with a type followed by a colon (e.g. <code>fn:</code>) to restrict the search to a given type. </p> <p> Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>. </p> <p> Search functions by type signature (e.g. <code>vec -> usize</code> or <code>* -> vec</code>) </p> </div> </div> </aside> <script> window.rootPath = "../"; window.currentCrate = "std"; </script> <script src="../main.js"></script> <script defer src="../search-index.js"></script> </body> </html>