628377c83b
This patch refactors the test suite: - Instead of always generating the documentation with the available rustdoc version, we now store generated documentation for all supported rustdoc versions in the test/html directory. - Instead of using one snapshot per test case, we now use one snapshot per test case and rustdoc version.
211 lines
23 KiB
HTML
211 lines
23 KiB
HTML
<!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 `log` crate."><meta name="keywords" content="rust, rustlang, rust-lang, log"><title>log - 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 mod"><!--[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><p class='location'>Crate log</p><div class="sidebar-elems"><a id='all-types' href='all.html'><p>See all log's items</p></a><div class="block items"><ul><li><a href="#macros">Macros</a></li><li><a href="#structs">Structs</a></li><li><a href="#enums">Enums</a></li><li><a href="#constants">Constants</a></li><li><a href="#traits">Traits</a></li><li><a href="#functions">Functions</a></li></ul></div><p class='location'></p><script>window.sidebarCurrent = {name: 'log', ty: 'mod', relpath: '../'};</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"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" disabled 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#11-1679' title='goto source code'>[src]</a></span><span class='in-band'>Crate <a class="mod" href=''>log</a></span></h1><div class='docblock'><p>A lightweight logging facade.</p>
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<p>The <code>log</code> crate provides a single logging API that abstracts over the
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actual logging implementation. Libraries can use the logging API provided
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by this crate, and the consumer of those libraries can choose the logging
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implementation that is most suitable for its use case.</p>
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<p>If no logging implementation is selected, the facade falls back to a "noop"
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implementation that ignores all log messages. The overhead in this case
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is very small - just an integer load, comparison and jump.</p>
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<p>A log request consists of a <em>target</em>, a <em>level</em>, and a <em>body</em>. A target is a
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string which defaults to the module path of the location of the log request,
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though that default may be overridden. Logger implementations typically use
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the target to filter requests based on some user configuration.</p>
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<h1 id="use" class="section-header"><a href="#use">Use</a></h1>
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<p>The basic use of the log crate is through the five logging macros: <a href="./macro.error.html"><code>error!</code></a>,
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<a href="./macro.warn.html"><code>warn!</code></a>, <a href="./macro.info.html"><code>info!</code></a>, <a href="./macro.debug.html"><code>debug!</code></a> and <a href="./macro.trace.html"><code>trace!</code></a>
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where <code>error!</code> represents the highest-priority log messages
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and <code>trace!</code> the lowest. The log messages are filtered by configuring
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the log level to exclude messages with a lower priority.
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Each of these macros accept format strings similarly to <a href="https://doc.rust-lang.org/stable/std/macro.println.html"><code>println!</code></a>.</p>
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<h2 id="in-libraries" class="section-header"><a href="#in-libraries">In libraries</a></h2>
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<p>Libraries should link only to the <code>log</code> crate, and use the provided
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macros to log whatever information will be useful to downstream consumers.</p>
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<h3 id="examples" class="section-header"><a href="#examples">Examples</a></h3>
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<div class='information'><div class='tooltip edition'>ⓘ<span class='tooltiptext'>This code runs with edition 2018</span></div></div><div class="example-wrap"><pre class="rust rust-example-rendered edition ">
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<span class="kw">use</span> <span class="ident">log</span>::{<span class="ident">info</span>, <span class="ident">warn</span>};
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<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">shave_the_yak</span>(<span class="ident">yak</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Yak</span>) {
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<span class="macro">info</span><span class="macro">!</span>(<span class="ident">target</span>: <span class="string">"yak_events"</span>, <span class="string">"Commencing yak shaving for {:?}"</span>, <span class="ident">yak</span>);
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<span class="kw">loop</span> {
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<span class="kw">match</span> <span class="ident">find_a_razor</span>() {
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<span class="prelude-val">Ok</span>(<span class="ident">razor</span>) <span class="op">=</span><span class="op">></span> {
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<span class="macro">info</span><span class="macro">!</span>(<span class="string">"Razor located: {}"</span>, <span class="ident">razor</span>);
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<span class="ident">yak</span>.<span class="ident">shave</span>(<span class="ident">razor</span>);
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<span class="kw">break</span>;
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}
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<span class="prelude-val">Err</span>(<span class="ident">err</span>) <span class="op">=</span><span class="op">></span> {
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<span class="macro">warn</span><span class="macro">!</span>(<span class="string">"Unable to locate a razor: {}, retrying"</span>, <span class="ident">err</span>);
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}
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}
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}
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}</pre></div>
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<h2 id="in-executables" class="section-header"><a href="#in-executables">In executables</a></h2>
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<p>Executables should choose a logging implementation and initialize it early in the
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runtime of the program. Logging implementations will typically include a
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function to do this. Any log messages generated before
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the implementation is initialized will be ignored.</p>
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<p>The executable itself may use the <code>log</code> crate to log as well.</p>
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<h3 id="warning" class="section-header"><a href="#warning">Warning</a></h3>
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<p>The logging system may only be initialized once.</p>
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<h1 id="available-logging-implementations" class="section-header"><a href="#available-logging-implementations">Available logging implementations</a></h1>
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<p>In order to produce log output executables have to use
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a logger implementation compatible with the facade.
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There are many available implementations to choose from,
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here are some of the most popular ones:</p>
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<ul>
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<li>Simple minimal loggers:
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<ul>
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<li><a href="https://docs.rs/env_logger/*/env_logger/">env_logger</a></li>
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<li><a href="https://github.com/borntyping/rust-simple_logger">simple_logger</a></li>
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<li><a href="https://github.com/drakulix/simplelog.rs">simplelog</a></li>
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<li><a href="https://docs.rs/pretty_env_logger/*/pretty_env_logger/">pretty_env_logger</a></li>
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<li><a href="https://docs.rs/stderrlog/*/stderrlog/">stderrlog</a></li>
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<li><a href="https://docs.rs/flexi_logger/*/flexi_logger/">flexi_logger</a></li>
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</ul>
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</li>
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<li>Complex configurable frameworks:
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<ul>
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<li><a href="https://docs.rs/log4rs/*/log4rs/">log4rs</a></li>
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<li><a href="https://docs.rs/fern/*/fern/">fern</a></li>
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</ul>
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</li>
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<li>Adaptors for other facilities:
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<ul>
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<li><a href="https://docs.rs/syslog/*/syslog/">syslog</a></li>
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<li><a href="https://docs.rs/slog-stdlog/*/slog_stdlog/">slog-stdlog</a></li>
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</ul>
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</li>
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</ul>
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<h1 id="implementing-a-logger" class="section-header"><a href="#implementing-a-logger">Implementing a Logger</a></h1>
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<p>Loggers implement the <a href="trait.Log.html"><code>Log</code></a> trait. Here's a very basic example that simply
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logs all messages at the <a href="enum.Level.html"><code>Error</code></a>, <a href="enum.Level.html"><code>Warn</code></a> or
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<a href="enum.Level.html"><code>Info</code></a> levels to stdout:</p>
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<div class='information'><div class='tooltip edition'>ⓘ<span class='tooltiptext'>This code runs with edition 2018</span></div></div><div class="example-wrap"><pre class="rust rust-example-rendered edition ">
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<span class="kw">use</span> <span class="ident">log</span>::{<span class="ident">Record</span>, <span class="ident">Level</span>, <span class="ident">Metadata</span>};
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<span class="kw">struct</span> <span class="ident">SimpleLogger</span>;
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<span class="kw">impl</span> <span class="ident">log</span>::<span class="ident">Log</span> <span class="kw">for</span> <span class="ident">SimpleLogger</span> {
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<span class="kw">fn</span> <span class="ident">enabled</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">metadata</span>: <span class="kw-2">&</span><span class="ident">Metadata</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
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<span class="ident">metadata</span>.<span class="ident">level</span>() <span class="op"><</span><span class="op">=</span> <span class="ident">Level</span>::<span class="ident">Info</span>
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}
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<span class="kw">fn</span> <span class="ident">log</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">record</span>: <span class="kw-2">&</span><span class="ident">Record</span>) {
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<span class="kw">if</span> <span class="self">self</span>.<span class="ident">enabled</span>(<span class="ident">record</span>.<span class="ident">metadata</span>()) {
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<span class="macro">println</span><span class="macro">!</span>(<span class="string">"{} - {}"</span>, <span class="ident">record</span>.<span class="ident">level</span>(), <span class="ident">record</span>.<span class="ident">args</span>());
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}
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}
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<span class="kw">fn</span> <span class="ident">flush</span>(<span class="kw-2">&</span><span class="self">self</span>) {}
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}
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</pre></div>
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<p>Loggers are installed by calling the <a href="fn.set_logger.html"><code>set_logger</code></a> function. The maximum
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log level also needs to be adjusted via the <a href="fn.set_max_level.html"><code>set_max_level</code></a> function. The
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logging facade uses this as an optimization to improve performance of log
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messages at levels that are disabled. It's important to set it, as it
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defaults to <a href="enum.LevelFilter.html"><code>Off</code></a>, so no log messages will ever be captured!
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In the case of our example logger, we'll want to set the maximum log level
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to <a href="enum.LevelFilter.html"><code>Info</code></a>, since we ignore any <a href="enum.Level.html"><code>Debug</code></a> or
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<a href="enum.Level.html"><code>Trace</code></a> level log messages. A logging implementation should
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provide a function that wraps a call to <a href="fn.set_logger.html"><code>set_logger</code></a> and
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<a href="fn.set_max_level.html"><code>set_max_level</code></a>, handling initialization of the logger:</p>
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<div class='information'><div class='tooltip edition'>ⓘ<span class='tooltiptext'>This code runs with edition 2018</span></div></div><div class="example-wrap"><pre class="rust rust-example-rendered edition ">
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<span class="kw">use</span> <span class="ident">log</span>::{<span class="ident">SetLoggerError</span>, <span class="ident">LevelFilter</span>};
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<span class="kw">static</span> <span class="ident">LOGGER</span>: <span class="ident">SimpleLogger</span> <span class="op">=</span> <span class="ident">SimpleLogger</span>;
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<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">init</span>() <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">SetLoggerError</span><span class="op">></span> {
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<span class="ident">log</span>::<span class="ident">set_logger</span>(<span class="kw-2">&</span><span class="ident">LOGGER</span>)
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.<span class="ident">map</span>(<span class="op">|</span>()<span class="op">|</span> <span class="ident">log</span>::<span class="ident">set_max_level</span>(<span class="ident">LevelFilter</span>::<span class="ident">Info</span>))
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}</pre></div>
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<p>Implementations that adjust their configurations at runtime should take care
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to adjust the maximum log level as well.</p>
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<h1 id="use-with-std" class="section-header"><a href="#use-with-std">Use with <code>std</code></a></h1>
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<p><code>set_logger</code> requires you to provide a <code>&'static Log</code>, which can be hard to
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obtain if your logger depends on some runtime configuration. The
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<code>set_boxed_logger</code> function is available with the <code>std</code> Cargo feature. It is
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identical to <code>set_logger</code> except that it takes a <code>Box<Log></code> rather than a
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<code>&'static Log</code>:</p>
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<div class='information'><div class='tooltip edition'>ⓘ<span class='tooltiptext'>This code runs with edition 2018</span></div></div><div class="example-wrap"><pre class="rust rust-example-rendered edition ">
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<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">init</span>() <span class="op">-</span><span class="op">></span> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">SetLoggerError</span><span class="op">></span> {
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<span class="ident">log</span>::<span class="ident">set_boxed_logger</span>(<span class="ident">Box</span>::<span class="ident">new</span>(<span class="ident">SimpleLogger</span>))
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.<span class="ident">map</span>(<span class="op">|</span>()<span class="op">|</span> <span class="ident">log</span>::<span class="ident">set_max_level</span>(<span class="ident">LevelFilter</span>::<span class="ident">Info</span>))
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}</pre></div>
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<h1 id="compile-time-filters" class="section-header"><a href="#compile-time-filters">Compile time filters</a></h1>
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<p>Log levels can be statically disabled at compile time via Cargo features. Log invocations at
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disabled levels will be skipped and will not even be present in the resulting binary.
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This level is configured separately for release and debug builds. The features are:</p>
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<ul>
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<li><code>max_level_off</code></li>
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<li><code>max_level_error</code></li>
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<li><code>max_level_warn</code></li>
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<li><code>max_level_info</code></li>
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<li><code>max_level_debug</code></li>
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<li><code>max_level_trace</code></li>
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<li><code>release_max_level_off</code></li>
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<li><code>release_max_level_error</code></li>
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<li><code>release_max_level_warn</code></li>
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<li><code>release_max_level_info</code></li>
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<li><code>release_max_level_debug</code></li>
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<li><code>release_max_level_trace</code></li>
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</ul>
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<p>These features control the value of the <code>STATIC_MAX_LEVEL</code> constant. The logging macros check
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this value before logging a message. By default, no levels are disabled.</p>
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<p>Libraries should avoid using the max level features because they're global and can't be changed
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once they're set.</p>
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<p>For example, a crate can disable trace level logs in debug builds and trace, debug, and info
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level logs in release builds with the following configuration:</p>
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<pre><code class="language-toml">[dependencies]
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log = { version = "0.4", features = ["max_level_debug", "release_max_level_warn"] }
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</code></pre>
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<h1 id="crate-feature-flags" class="section-header"><a href="#crate-feature-flags">Crate Feature Flags</a></h1>
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<p>The following crate feature flags are available in addition to the filters. They are
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configured in your <code>Cargo.toml</code>.</p>
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<ul>
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<li><code>std</code> allows use of <code>std</code> crate instead of the default <code>core</code>. Enables using <code>std::error</code> and
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<code>set_boxed_logger</code> functionality.</li>
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<li><code>serde</code> enables support for serialization and deserialization of <code>Level</code> and <code>LevelFilter</code>.</li>
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</ul>
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<pre><code class="language-toml">[dependencies]
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log = { version = "0.4", features = ["std", "serde"] }
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</code></pre>
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<h1 id="version-compatibility" class="section-header"><a href="#version-compatibility">Version compatibility</a></h1>
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<p>The 0.3 and 0.4 versions of the <code>log</code> crate are almost entirely compatible. Log messages
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made using <code>log</code> 0.3 will forward transparently to a logger implementation using <code>log</code> 0.4. Log
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messages made using <code>log</code> 0.4 will forward to a logger implementation using <code>log</code> 0.3, but the
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module path and file name information associated with the message will unfortunately be lost.</p>
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</div><h2 id='macros' class='section-header'><a href="#macros">Macros</a></h2>
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<table><tr class='module-item'><td><a class="macro" href="macro.debug.html" title='log::debug macro'>debug</a></td><td class='docblock-short'><p>Logs a message at the debug level.</p>
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||
</td></tr><tr class='module-item'><td><a class="macro" href="macro.error.html" title='log::error macro'>error</a></td><td class='docblock-short'><p>Logs a message at the error level.</p>
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||
</td></tr><tr class='module-item'><td><a class="macro" href="macro.info.html" title='log::info macro'>info</a></td><td class='docblock-short'><p>Logs a message at the info level.</p>
|
||
</td></tr><tr class='module-item'><td><a class="macro" href="macro.log.html" title='log::log macro'>log</a></td><td class='docblock-short'><p>The standard logging macro.</p>
|
||
</td></tr><tr class='module-item'><td><a class="macro" href="macro.log_enabled.html" title='log::log_enabled macro'>log_enabled</a></td><td class='docblock-short'><p>Determines if a message logged at the specified level in that module will
|
||
be logged.</p>
|
||
</td></tr><tr class='module-item'><td><a class="macro" href="macro.trace.html" title='log::trace macro'>trace</a></td><td class='docblock-short'><p>Logs a message at the trace level.</p>
|
||
</td></tr><tr class='module-item'><td><a class="macro" href="macro.warn.html" title='log::warn macro'>warn</a></td><td class='docblock-short'><p>Logs a message at the warn level.</p>
|
||
</td></tr></table><h2 id='structs' class='section-header'><a href="#structs">Structs</a></h2>
|
||
<table><tr class='module-item'><td><a class="struct" href="struct.Metadata.html" title='log::Metadata struct'>Metadata</a></td><td class='docblock-short'><p>Metadata about a log message.</p>
|
||
</td></tr><tr class='module-item'><td><a class="struct" href="struct.MetadataBuilder.html" title='log::MetadataBuilder struct'>MetadataBuilder</a></td><td class='docblock-short'><p>Builder for <a href="struct.Metadata.html"><code>Metadata</code></a>.</p>
|
||
</td></tr><tr class='module-item'><td><a class="struct" href="struct.ParseLevelError.html" title='log::ParseLevelError struct'>ParseLevelError</a></td><td class='docblock-short'><p>The type returned by <a href="https://doc.rust-lang.org/std/str/trait.FromStr.html#tymethod.from_str"><code>from_str</code></a> when the string doesn't match any of the log levels.</p>
|
||
</td></tr><tr class='module-item'><td><a class="struct" href="struct.Record.html" title='log::Record struct'>Record</a></td><td class='docblock-short'><p>The "payload" of a log message.</p>
|
||
</td></tr><tr class='module-item'><td><a class="struct" href="struct.RecordBuilder.html" title='log::RecordBuilder struct'>RecordBuilder</a></td><td class='docblock-short'><p>Builder for <a href="struct.Record.html"><code>Record</code></a>.</p>
|
||
</td></tr><tr class='module-item'><td><a class="struct" href="struct.SetLoggerError.html" title='log::SetLoggerError struct'>SetLoggerError</a></td><td class='docblock-short'><p>The type returned by <a href="fn.set_logger.html"><code>set_logger</code></a> if <a href="fn.set_logger.html"><code>set_logger</code></a> has already been called.</p>
|
||
</td></tr></table><h2 id='enums' class='section-header'><a href="#enums">Enums</a></h2>
|
||
<table><tr class='module-item'><td><a class="enum" href="enum.Level.html" title='log::Level enum'>Level</a></td><td class='docblock-short'><p>An enum representing the available verbosity levels of the logger.</p>
|
||
</td></tr><tr class='module-item'><td><a class="enum" href="enum.LevelFilter.html" title='log::LevelFilter enum'>LevelFilter</a></td><td class='docblock-short'><p>An enum representing the available verbosity level filters of the logger.</p>
|
||
</td></tr></table><h2 id='constants' class='section-header'><a href="#constants">Constants</a></h2>
|
||
<table><tr class='module-item'><td><a class="constant" href="constant.STATIC_MAX_LEVEL.html" title='log::STATIC_MAX_LEVEL constant'>STATIC_MAX_LEVEL</a></td><td class='docblock-short'><p>The statically resolved maximum log level.</p>
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</td></tr></table><h2 id='traits' class='section-header'><a href="#traits">Traits</a></h2>
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<table><tr class='module-item'><td><a class="trait" href="trait.Log.html" title='log::Log trait'>Log</a></td><td class='docblock-short'><p>A trait encapsulating the operations required of a logger.</p>
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</td></tr></table><h2 id='functions' class='section-header'><a href="#functions">Functions</a></h2>
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<table><tr class='module-item'><td><a class="fn" href="fn.logger.html" title='log::logger fn'>logger</a></td><td class='docblock-short'><p>Returns a reference to the logger.</p>
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</td></tr><tr class='module-item'><td><a class="fn" href="fn.max_level.html" title='log::max_level fn'>max_level</a></td><td class='docblock-short'><p>Returns the current maximum log level.</p>
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</td></tr><tr class='module-item'><td><a class="fn" href="fn.set_boxed_logger.html" title='log::set_boxed_logger fn'>set_boxed_logger</a></td><td class='docblock-short'><p>Sets the global logger to a <code>Box<Log></code>.</p>
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</td></tr><tr class='module-item'><td><a class="fn" href="fn.set_logger.html" title='log::set_logger fn'>set_logger</a></td><td class='docblock-short'><p>Sets the global logger to a <code>&'static Log</code>.</p>
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</td></tr><tr class='module-item'><td><a class="fn" href="fn.set_logger_racy.html" title='log::set_logger_racy fn'>set_logger_racy</a><a title='unsafe function' href='#'><sup>⚠</sup></a></td><td class='docblock-short'><p>A thread-unsafe version of <a href="fn.set_logger.html"><code>set_logger</code></a>.</p>
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</td></tr><tr class='module-item'><td><a class="fn" href="fn.set_max_level.html" title='log::set_max_level fn'>set_max_level</a></td><td class='docblock-short'><p>Sets the global maximum log level.</p>
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