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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="API documentation for the Rust `set_logger` fn in crate `log`."><meta name="keywords" content="rust, rustlang, rust-lang, set_logger"><title>log::set_logger - Rust</title><link rel="stylesheet" type="text/css" href="../normalize.css"><link rel="stylesheet" type="text/css" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../dark.css"><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script src="../storage.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="shortcut icon" href="https://www.rust-lang.org/favicon.ico"><style type="text/css">#crate-search{background-image:url("../down-arrow.svg");}</style></head><body class="rustdoc fn"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../log/index.html'><div class='logo-container'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo'></div></a><div class="sidebar-elems"><p class='location'><a href='index.html'>log</a></p><script>window.sidebarCurrent = {name: 'set_logger', ty: 'fn', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><a id="settings-menu" href="../settings.html"><img src="../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><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><a class='srclink' href='../src/log/lib.rs.html#1260-1262' title='goto source code'>[src]</a></span><span class='in-band'>Function <a href='index.html'>log</a>::<wbr><a class="fn" href=''>set_logger</a></span></h1><pre class='rust fn'>pub fn set_logger(logger: &'static dyn <a class="trait" href="../log/trait.Log.html" title="trait log::Log">Log</a>) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, <a class="struct" href="../log/struct.SetLoggerError.html" title="struct log::SetLoggerError">SetLoggerError</a>></pre><div class='docblock'><p>Sets the global logger to a <code>&'static Log</code>.</p>
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<p>This function may only be called once in the lifetime of a program. Any log
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events that occur before the call to <code>set_logger</code> completes will be ignored.</p>
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<p>This function does not typically need to be called manually. Logger
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implementations should provide an initialization method that installs the
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logger internally.</p>
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<h1 id="availability" class="section-header"><a href="#availability">Availability</a></h1>
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<p>This method is available even when the <code>std</code> feature is disabled. However,
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it is currently unavailable on <code>thumbv6</code> targets, which lack support for
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some atomic operations which are used by this function. Even on those
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targets, <a href="fn.set_logger_racy.html"><code>set_logger_racy</code></a> will be available.</p>
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<h1 id="errors" class="section-header"><a href="#errors">Errors</a></h1>
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<p>An error is returned if a logger has already been set.</p>
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<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
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<pre><code class="language-edition2018">use log::{error, info, warn, Record, Level, Metadata, LevelFilter};
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static MY_LOGGER: MyLogger = MyLogger;
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struct MyLogger;
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impl log::Log for MyLogger {
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fn enabled(&self, metadata: &Metadata) -> bool {
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metadata.level() <= Level::Info
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}
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fn log(&self, record: &Record) {
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if self.enabled(record.metadata()) {
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println!("{} - {}", record.level(), record.args());
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}
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}
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fn flush(&self) {}
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}
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# fn main(){
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log::set_logger(&MY_LOGGER).unwrap();
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log::set_max_level(LevelFilter::Info);
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info!("hello log");
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warn!("warning");
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error!("oops");
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# }
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</code></pre>
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