<!DOCTYPE html><htmllang="en"><head><metacharset="utf-8"><metaname="viewport"content="width=device-width, initial-scale=1.0"><metaname="generator"content="rustdoc"><metaname="description"content="Prints to `stdout`, with a newline."><title>println in anstream - Rust</title><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><linkrel="stylesheet"href="../static.files/normalize-76eba96aa4d2e634.css"><linkrel="stylesheet"href="../static.files/rustdoc-ac92e1bbe349e143.css"><metaname="rustdoc-vars"data-root-path="../"data-static-root-path="../static.files/"data-current-crate="anstream"data-themes=""data-resource-suffix=""data-rustdoc-version="1.76.0 (07dca489a 2024-02-04)"data-channel="1.76.0"data-search-js="search-2b6ce74ff89ae146.js"data-settings-js="settings-4313503d2e1961c2.js"><scriptsrc="../static.files/storage-f2adc0d6ca4d09fb.js"></script><scriptdefersrc="sidebar-items.js"></script><scriptdefersrc="../static.files/main-305769736d49e732.js"></script><noscript><linkrel="stylesheet"href="../static.files/noscript-feafe1bb7466e4bd.css"></noscript><linkrel="alternate icon"type="image/png"href="../static.files/favicon-16x16-8b506e7a72182f1c.png"><linkrel="alternate icon"type="image/png"href="../static.files/favicon-32x32-422f7d1d52889060.png"><linkrel="icon"type="image/svg+xml"href="../static.files/favicon-2c020d218678b618.svg"></head><bodyclass="rustdoc macro"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><navclass="mobile-topbar"><buttonclass="sidebar-menu-toggle">☰</button></nav><navclass="sidebar"><divclass="sidebar-crate"><h2><ahref="../anstream/index.html">anstream</a><spanclass="version">0.6.12</span></h2></div><divclass="sidebar-elems"></div></nav><divclass="sidebar-resizer"></div>
<main><divclass="width-limiter"><navclass="sub"><formclass="search-form"><span></span><divid="sidebar-button"tabindex="-1"><ahref="../anstream/all.html"title="show sidebar"></a></div><inputclass="search-input"name="search"aria-label="Run search in the documentation"autocomplete="off"spellcheck="false"placeholder="Click or press ‘S’ to search, ‘?’ for more options…"type="search"><divid="help-button"tabindex="-1"><ahref="../help.html"title="help">?</a></div><divid="settings-menu"tabindex="-1"><ahref="../settings.html"title="settings"><imgwidth="22"height="22"alt="Change settings"src="../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><sectionid="main-content"class="content"><divclass="main-heading"><h1>Macro <ahref="index.html">anstream</a>::<wbr><aclass="macro"href="#">println</a><buttonid="copy-path"title="Copy item path to clipboard"><imgsrc="../static.files/clipboard-7571035ce49a181d.svg"width="19"height="18"alt="Copy item path"></button></h1><spanclass="out-of-band"><aclass="src"href="../src/anstream/macros.rs.html#139-169">source</a> · <buttonid="toggle-all-docs"title="collapse all docs">[<span>−</span>]</button></span></div><preclass="rust item-decl"><spanclass="macro">macro_rules! </span>println {
}</pre><detailsclass="toggle top-doc"open><summaryclass="hideme"><span>Expand description</span></summary><divclass="docblock"><p>Prints to <ahref="fn.stdout.html"title="fn anstream::stdout"><code>stdout</code></a>, with a newline.</p>
<p>On all platforms, the newline is the LINE FEED character (<code>\n</code>/<code>U+000A</code>) alone
(no additional CARRIAGE RETURN (<code>\r</code>/<code>U+000D</code>)).</p>
<p>This macro uses the same syntax as <ahref="https://doc.rust-lang.org/1.76.0/alloc/macro.format.html"title="macro alloc::format"><code>format!</code></a>, but writes to the standard output instead.
See <ahref="https://doc.rust-lang.org/1.76.0/alloc/fmt/index.html"title="mod alloc::fmt"><code>std::fmt</code></a> for more information.</p>
<p><strong>NOTE:</strong> The <code>println!</code> macro will lock the standard output on each call. If you call
<code>println!</code> within a hot loop, this behavior may be the bottleneck of the loop.
To avoid this, lock stdout with <ahref="struct.AutoStream.html#method.lock"title="method anstream::AutoStream::lock"><code>AutoStream::lock</code></a>:</p>
<p>Use <code>println!</code> only for the primary output of your program. Use
<ahref="https://doc.rust-lang.org/1.76.0/std/macro.eprintln.html"title="macro std::eprintln"><code>eprintln!</code></a> instead to print error and progress messages.</p>
<p><strong>NOTE:</strong> Not all <code>println!</code> calls will be captured in tests like <ahref="https://doc.rust-lang.org/1.76.0/std/macro.println.html"title="macro std::println"><code>std::println!</code></a></p>
<ul>
<li>Capturing will automatically be activated in test binaries</li>
<li>Otherwise, only when the <code>test</code> feature is enabled</li>
</ul>
<h2id="panics"><ahref="#panics">Panics</a></h2>
<p>Panics if writing to <code>stdout</code> fails for any reason <strong>except</strong> broken pipe.</p>
<p>Writing to non-blocking stdout can cause an error, which will lead
