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<!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="Sets the global logger to a `&amp;&#x27;static Log`."><title>set_logger in log - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><link rel="stylesheet" href="../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../static.files/rustdoc-ac92e1bbe349e143.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="log" 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" ><script src="../static.files/storage-f2adc0d6ca4d09fb.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-305769736d49e732.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-feafe1bb7466e4bd.css"></noscript><link rel="icon" href="https://www.rust-lang.org/favicon.ico"></head><body class="rustdoc fn"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">&#9776;</button><a class="logo-container" href="../log/index.html"><img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png" alt=""></a></nav><nav class="sidebar"><div class="sidebar-crate"><a class="logo-container" href="../log/index.html"><img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png" alt="logo"></a><h2><a href="../log/index.html">log</a><span class="version">0.4.20</span></h2></div><div class="sidebar-elems"></div></nav><div class="sidebar-resizer"></div>
<main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><div id="sidebar-button" tabindex="-1"><a href="../log/all.html" title="show sidebar"></a></div><input class="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"><div id="help-button" tabindex="-1"><a href="../help.html" title="help">?</a></div><div id="settings-menu" tabindex="-1"><a href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1>Function <a href="index.html">log</a>::<wbr><a class="fn" href="#">set_logger</a><button id="copy-path" title="Copy item path to clipboard"><img src="../static.files/clipboard-7571035ce49a181d.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="src" href="../src/log/lib.rs.html#1352-1354">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>&#x2212;</span>]</button></span></div><pre class="rust item-decl"><code>pub fn set_logger(logger: &amp;'static dyn <a class="trait" href="trait.Log.html" title="trait log::Log">Log</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/1.76.0/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/1.76.0/std/primitive.unit.html">()</a>, <a class="struct" href="struct.SetLoggerError.html" title="struct log::SetLoggerError">SetLoggerError</a>&gt;</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Sets the global logger to a <code>&amp;'static Log</code>.</p>
<p>This function may only be called once in the lifetime of a program. Any log
events that occur before the call to <code>set_logger</code> completes will be ignored.</p>
<p>This function does not typically need to be called manually. Logger
implementations should provide an initialization method that installs the
logger internally.</p>
<h2 id="availability"><a href="#availability">Availability</a></h2>
<p>This method is available even when the <code>std</code> feature is disabled. However,
it is currently unavailable on <code>thumbv6</code> targets, which lack support for
some atomic operations which are used by this function. Even on those
targets, <a href="fn.set_logger_racy.html"><code>set_logger_racy</code></a> will be available.</p>
<h2 id="errors"><a href="#errors">Errors</a></h2>
<p>An error is returned if a logger has already been set.</p>
<h2 id="examples"><a href="#examples">Examples</a></h2>
<div class="example-wrap edition"><a href="#" class="tooltip" title="This example runs with edition 2018"></a><pre class="rust rust-example-rendered"><code><span class="kw">use </span>log::{error, info, warn, Record, Level, Metadata, LevelFilter};
<span class="kw">static </span>MY_LOGGER: MyLogger = MyLogger;
<span class="kw">struct </span>MyLogger;
<span class="kw">impl </span>log::Log <span class="kw">for </span>MyLogger {
<span class="kw">fn </span>enabled(<span class="kw-2">&amp;</span><span class="self">self</span>, metadata: <span class="kw-2">&amp;</span>Metadata) -&gt; bool {
metadata.level() &lt;= Level::Info
}
<span class="kw">fn </span>log(<span class="kw-2">&amp;</span><span class="self">self</span>, record: <span class="kw-2">&amp;</span>Record) {
<span class="kw">if </span><span class="self">self</span>.enabled(record.metadata()) {
<span class="macro">println!</span>(<span class="string">"{} - {}"</span>, record.level(), record.args());
}
}
<span class="kw">fn </span>flush(<span class="kw-2">&amp;</span><span class="self">self</span>) {}
}
log::set_logger(<span class="kw-2">&amp;</span>MY_LOGGER).unwrap();
log::set_max_level(LevelFilter::Info);
<span class="macro">info!</span>(<span class="string">"hello log"</span>);
<span class="macro">warn!</span>(<span class="string">"warning"</span>);
<span class="macro">error!</span>(<span class="string">"oops"</span>);</code></pre></div>
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