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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="Extension trait adding combinators for working with types implementing `MakeWriter`."><title>MakeWriterExt in tracing_subscriber::fmt::writer - 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="tracing_subscriber" 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="alternate icon" type="image/png" href="../../../static.files/favicon-16x16-8b506e7a72182f1c.png"><link rel="alternate icon" type="image/png" href="../../../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../../../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc trait"><!--[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">☰</button><a class="logo-container" href="../../../tracing_subscriber/index.html"><img src="https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png" alt=""></a></nav><nav class="sidebar"><div class="sidebar-crate"><a class="logo-container" href="../../../tracing_subscriber/index.html"><img src="https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png" alt="logo"></a><h2><a href="../../../tracing_subscriber/index.html">tracing_subscriber</a><span class="version">0.3.18</span></h2></div><h2 class="location"><a href="#">MakeWriterExt</a></h2><div class="sidebar-elems"><section><h3><a href="#provided-methods">Provided Methods</a></h3><ul class="block"><li><a href="#method.and">and</a></li><li><a href="#method.or_else">or_else</a></li><li><a href="#method.with_filter">with_filter</a></li><li><a href="#method.with_max_level">with_max_level</a></li><li><a href="#method.with_min_level">with_min_level</a></li></ul><h3><a href="#implementors">Implementors</a></h3></section><h2><a href="index.html">In tracing_subscriber::fmt::writer</a></h2></div></nav><div class="sidebar-resizer"></div>
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<main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><div id="sidebar-button" tabindex="-1"><a href="../../../tracing_subscriber/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>Trait <a href="../../index.html">tracing_subscriber</a>::<wbr><a href="../index.html">fmt</a>::<wbr><a href="index.html">writer</a>::<wbr><a class="trait" href="#">MakeWriterExt</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/tracing_subscriber/fmt/writer.rs.html#217-491">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>−</span>]</button></span></div><pre class="rust item-decl"><code>pub trait MakeWriterExt<'a>: <a class="trait" href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter">MakeWriter</a><'a> {
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// Provided methods
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fn <a href="#method.with_max_level" class="fn">with_max_level</a>(self, level: <a class="struct" href="../../../tracing_core/metadata/struct.Level.html" title="struct tracing_core::metadata::Level">Level</a>) -> <a class="struct" href="struct.WithMaxLevel.html" title="struct tracing_subscriber::fmt::writer::WithMaxLevel">WithMaxLevel</a><Self>
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<span class="where">where Self: <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a></span> { ... }
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<span class="item-spacer"></span> fn <a href="#method.with_min_level" class="fn">with_min_level</a>(self, level: <a class="struct" href="../../../tracing_core/metadata/struct.Level.html" title="struct tracing_core::metadata::Level">Level</a>) -> <a class="struct" href="struct.WithMinLevel.html" title="struct tracing_subscriber::fmt::writer::WithMinLevel">WithMinLevel</a><Self>
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<span class="where">where Self: <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a></span> { ... }
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<span class="item-spacer"></span> fn <a href="#method.with_filter" class="fn">with_filter</a><F>(self, filter: F) -> <a class="struct" href="struct.WithFilter.html" title="struct tracing_subscriber::fmt::writer::WithFilter">WithFilter</a><Self, F>
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<span class="where">where Self: <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,
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F: <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/ops/function/trait.Fn.html" title="trait core::ops::function::Fn">Fn</a>(&<a class="struct" href="../../../tracing_core/metadata/struct.Metadata.html" title="struct tracing_core::metadata::Metadata">Metadata</a><'_>) -> <a class="primitive" href="https://doc.rust-lang.org/1.76.0/std/primitive.bool.html">bool</a></span> { ... }
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<span class="item-spacer"></span> fn <a href="#method.and" class="fn">and</a><B>(self, other: B) -> <a class="struct" href="struct.Tee.html" title="struct tracing_subscriber::fmt::writer::Tee">Tee</a><Self, B> <a href="#" class="tooltip" data-notable-ty="Tee<Self, B>">ⓘ</a>
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<span class="where">where Self: <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,
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B: <a class="trait" href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter">MakeWriter</a><'a> + <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a></span> { ... }
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<span class="item-spacer"></span> fn <a href="#method.or_else" class="fn">or_else</a><W, B>(self, other: B) -> <a class="struct" href="struct.OrElse.html" title="struct tracing_subscriber::fmt::writer::OrElse">OrElse</a><Self, B>
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<span class="where">where Self: <a class="trait" href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter">MakeWriter</a><'a, Writer = <a class="type" href="type.OptionalWriter.html" title="type tracing_subscriber::fmt::writer::OptionalWriter">OptionalWriter</a><W>> + <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,
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B: <a class="trait" href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter">MakeWriter</a><'a> + <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,
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W: <a class="trait" href="https://doc.rust-lang.org/1.76.0/std/io/trait.Write.html" title="trait std::io::Write">Write</a></span> { ... }
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}</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Extension trait adding combinators for working with types implementing
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<a href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a>.</p>
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<p>This is not intended to be implemented directly for user-defined
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<a href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a>s; instead, it should be imported when the desired methods are
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used.</p>
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</div></details><h2 id="provided-methods" class="section-header">Provided Methods<a href="#provided-methods" class="anchor">§</a></h2><div class="methods"><details class="toggle method-toggle" open><summary><section id="method.with_max_level" class="method"><a class="src rightside" href="../../../src/tracing_subscriber/fmt/writer.rs.html#276-281">source</a><h4 class="code-header">fn <a href="#method.with_max_level" class="fn">with_max_level</a>(self, level: <a class="struct" href="../../../tracing_core/metadata/struct.Level.html" title="struct tracing_core::metadata::Level">Level</a>) -> <a class="struct" href="struct.WithMaxLevel.html" title="struct tracing_subscriber::fmt::writer::WithMaxLevel">WithMaxLevel</a><Self><div class="where">where
|
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Self: <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,</div></h4></section></summary><div class="docblock"><p>Wraps <code>self</code> and returns a <a href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a> that will only write output
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for events at or below the provided verbosity <a href="../../../tracing_core/metadata/struct.Level.html" title="struct tracing_core::metadata::Level"><code>Level</code></a>. For instance,
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<code>Level::TRACE</code> is considered to be _more verbose<code>than</code>Level::INFO`.</p>
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<p>Events whose level is more verbose than <code>level</code> will be ignored, and no
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output will be written.</p>
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<h5 id="examples"><a href="#examples">Examples</a></h5>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tracing::Level;
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<span class="kw">use </span>tracing_subscriber::fmt::writer::MakeWriterExt;
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<span class="comment">// Construct a writer that outputs events to `stderr` only if the span or
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// event's level is >= WARN (WARN and ERROR).
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</span><span class="kw">let </span>mk_writer = std::io::stderr.with_max_level(Level::WARN);
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tracing_subscriber::fmt().with_writer(mk_writer).init();</code></pre></div>
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<p>Writing the <code>ERROR</code> and <code>WARN</code> levels to <code>stderr</code>, and everything else
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to <code>stdout</code>:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code>
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<span class="kw">let </span>mk_writer = std::io::stderr
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.with_max_level(Level::WARN)
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.or_else(std::io::stdout);
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tracing_subscriber::fmt().with_writer(mk_writer).init();</code></pre></div>
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<p>Writing the <code>ERROR</code> level to <code>stderr</code>, the <code>INFO</code> and <code>WARN</code> levels to
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<code>stdout</code>, and the <code>INFO</code> and DEBUG` levels to a file:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::{sync::Arc, fs::File};
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<span class="kw">let </span>debug_log = Arc::new(File::create(<span class="string">"debug.log"</span>)<span class="question-mark">?</span>);
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<span class="kw">let </span>mk_writer = std::io::stderr
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.with_max_level(Level::ERROR)
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.or_else(std::io::stdout
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.with_max_level(Level::INFO)
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.and(debug_log.with_max_level(Level::DEBUG))
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);
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tracing_subscriber::fmt().with_writer(mk_writer).init();</code></pre></div>
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</div></details><details class="toggle method-toggle" open><summary><section id="method.with_min_level" class="method"><a class="src rightside" href="../../../src/tracing_subscriber/fmt/writer.rs.html#318-323">source</a><h4 class="code-header">fn <a href="#method.with_min_level" class="fn">with_min_level</a>(self, level: <a class="struct" href="../../../tracing_core/metadata/struct.Level.html" title="struct tracing_core::metadata::Level">Level</a>) -> <a class="struct" href="struct.WithMinLevel.html" title="struct tracing_subscriber::fmt::writer::WithMinLevel">WithMinLevel</a><Self><div class="where">where
|
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Self: <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,</div></h4></section></summary><div class="docblock"><p>Wraps <code>self</code> and returns a <a href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a> that will only write output
|
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for events at or above the provided verbosity <a href="../../../tracing_core/metadata/struct.Level.html" title="struct tracing_core::metadata::Level"><code>Level</code></a>.</p>
|
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<p>Events whose level is less verbose than <code>level</code> will be ignored, and no
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output will be written.</p>
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<h5 id="examples-1"><a href="#examples-1">Examples</a></h5>
|
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tracing::Level;
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<span class="kw">use </span>tracing_subscriber::fmt::writer::MakeWriterExt;
|
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<span class="comment">// Construct a writer that outputs events to `stdout` only if the span or
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// event's level is <= DEBUG (DEBUG and TRACE).
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</span><span class="kw">let </span>mk_writer = std::io::stdout.with_min_level(Level::DEBUG);
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tracing_subscriber::fmt().with_writer(mk_writer).init();</code></pre></div>
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<p>This can be combined with <a href="trait.MakeWriterExt.html#method.with_max_level" title="method tracing_subscriber::fmt::writer::MakeWriterExt::with_max_level"><code>MakeWriterExt::with_max_level</code></a> to write
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only within a range of levels:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="comment">// Only write the `DEBUG` and `INFO` levels to stdout.
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</span><span class="kw">let </span>mk_writer = std::io::stdout
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.with_max_level(Level::DEBUG)
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.with_min_level(Level::INFO)
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<span class="comment">// Write the `WARN` and `ERROR` levels to stderr.
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</span>.and(std::io::stderr.with_min_level(Level::WARN));
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tracing_subscriber::fmt().with_writer(mk_writer).init();</code></pre></div>
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</div></details><details class="toggle method-toggle" open><summary><section id="method.with_filter" class="method"><a class="src rightside" href="../../../src/tracing_subscriber/fmt/writer.rs.html#397-403">source</a><h4 class="code-header">fn <a href="#method.with_filter" class="fn">with_filter</a><F>(self, filter: F) -> <a class="struct" href="struct.WithFilter.html" title="struct tracing_subscriber::fmt::writer::WithFilter">WithFilter</a><Self, F><div class="where">where
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Self: <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,
|
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F: <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/ops/function/trait.Fn.html" title="trait core::ops::function::Fn">Fn</a>(&<a class="struct" href="../../../tracing_core/metadata/struct.Metadata.html" title="struct tracing_core::metadata::Metadata">Metadata</a><'_>) -> <a class="primitive" href="https://doc.rust-lang.org/1.76.0/std/primitive.bool.html">bool</a>,</div></h4></section></summary><div class="docblock"><p>Wraps <code>self</code> with a predicate that takes a span or event’s <a href="../../../tracing_core/metadata/struct.Metadata.html" title="struct tracing_core::metadata::Metadata"><code>Metadata</code></a>
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and returns a <code>bool</code>. The returned <a href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a>’s
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<a href="../trait.MakeWriter.html#method.make_writer_for" title="method tracing_subscriber::fmt::MakeWriter::make_writer_for"><code>MakeWriter::make_writer_for</code></a> method will check the predicate to
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determine if a writer should be produced for a given span or event.</p>
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<p>If the predicate returns <code>false</code>, the wrapped <a href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a>’s
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<a href="../trait.MakeWriter.html#method.make_writer_for" title="method tracing_subscriber::fmt::MakeWriter::make_writer_for"><code>make_writer_for</code></a> will return <a href="enum.EitherWriter.html#method.none" title="associated function tracing_subscriber::fmt::writer::EitherWriter::none"><code>OptionalWriter::none</code></a>.
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Otherwise, it calls the wrapped <a href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a>’s
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<a href="../trait.MakeWriter.html#method.make_writer_for" title="method tracing_subscriber::fmt::MakeWriter::make_writer_for"><code>make_writer_for</code></a> method, and returns the produced writer.</p>
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<p>This can be used to filter an output based on arbitrary <a href="../../../tracing_core/metadata/struct.Metadata.html" title="struct tracing_core::metadata::Metadata"><code>Metadata</code></a>
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parameters.</p>
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<h5 id="examples-2"><a href="#examples-2">Examples</a></h5>
|
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<p>Writing events with a specific target to an HTTP access log, and other
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events to stdout:</p>
|
||
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tracing_subscriber::fmt::writer::MakeWriterExt;
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<span class="kw">use </span>std::{sync::Arc, fs::File};
|
||
<span class="kw">let </span>access_log = Arc::new(File::create(<span class="string">"access.log"</span>)<span class="question-mark">?</span>);
|
||
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<span class="kw">let </span>mk_writer = access_log
|
||
<span class="comment">// Only write events with the target "http::access_log" to the
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// access log file.
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</span>.with_filter(|meta| meta.target() == <span class="string">"http::access_log"</span>)
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<span class="comment">// Write events with all other targets to stdout.
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</span>.or_else(std::io::stdout);
|
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tracing_subscriber::fmt().with_writer(mk_writer).init();</code></pre></div>
|
||
<p>Conditionally enabling or disabling a log file:</p>
|
||
|
||
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tracing_subscriber::fmt::writer::MakeWriterExt;
|
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<span class="kw">use </span>std::{
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sync::{Arc, atomic::{AtomicBool, Ordering}},
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fs::File,
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};
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<span class="kw">static </span>DEBUG_LOG_ENABLED: AtomicBool = AtomicBool::new(<span class="bool-val">false</span>);
|
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<span class="comment">// Create the debug log file
|
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</span><span class="kw">let </span>debug_file = Arc::new(File::create(<span class="string">"debug.log"</span>)<span class="question-mark">?</span>)
|
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<span class="comment">// Enable the debug log only if the flag is enabled.
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</span>.with_filter(|<span class="kw">_</span>| DEBUG_LOG_ENABLED.load(Ordering::Acquire));
|
||
|
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<span class="comment">// Always write to stdout
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</span><span class="kw">let </span>mk_writer = std::io::stdout
|
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<span class="comment">// Write to the debug file if it's enabled
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</span>.and(debug_file);
|
||
|
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tracing_subscriber::fmt().with_writer(mk_writer).init();
|
||
|
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<span class="comment">// ...
|
||
|
||
// Later, we can toggle on or off the debug log file.
|
||
</span>DEBUG_LOG_ENABLED.store(<span class="bool-val">true</span>, Ordering::Release);</code></pre></div>
|
||
</div></details><details class="toggle method-toggle" open><summary><section id="method.and" class="method"><a class="src rightside" href="../../../src/tracing_subscriber/fmt/writer.rs.html#452-458">source</a><h4 class="code-header">fn <a href="#method.and" class="fn">and</a><B>(self, other: B) -> <a class="struct" href="struct.Tee.html" title="struct tracing_subscriber::fmt::writer::Tee">Tee</a><Self, B> <a href="#" class="tooltip" data-notable-ty="Tee<Self, B>">ⓘ</a><div class="where">where
|
||
Self: <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,
|
||
B: <a class="trait" href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter">MakeWriter</a><'a> + <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,</div></h4></section></summary><div class="docblock"><p>Combines <code>self</code> with another type implementing <a href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a>, returning
|
||
a new <a href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a> that produces <a href="https://doc.rust-lang.org/1.76.0/std/io/trait.Write.html" title="trait std::io::Write">writers</a> that write to <em>both</em>
|
||
outputs.</p>
|
||
<p>If writing to either writer returns an error, the returned writer will
|
||
return that error. However, both writers will still be written to before
|
||
the error is returned, so it is possible for one writer to fail while
|
||
the other is written to successfully.</p>
|
||
<h5 id="examples-3"><a href="#examples-3">Examples</a></h5>
|
||
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tracing_subscriber::fmt::writer::MakeWriterExt;
|
||
|
||
<span class="comment">// Construct a writer that outputs events to `stdout` *and* `stderr`.
|
||
</span><span class="kw">let </span>mk_writer = std::io::stdout.and(std::io::stderr);
|
||
|
||
tracing_subscriber::fmt().with_writer(mk_writer).init();</code></pre></div>
|
||
<p><code>and</code> can be used in conjunction with filtering combinators. For
|
||
example, if we want to write to a number of outputs depending on the
|
||
level of an event, we could write:</p>
|
||
|
||
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tracing::Level;
|
||
<span class="kw">use </span>std::{sync::Arc, fs::File};
|
||
<span class="kw">let </span>debug_log = Arc::new(File::create(<span class="string">"debug.log"</span>)<span class="question-mark">?</span>);
|
||
|
||
<span class="comment">// Write everything to the debug log.
|
||
</span><span class="kw">let </span>mk_writer = debug_log
|
||
<span class="comment">// Write the `ERROR` and `WARN` levels to stderr.
|
||
</span>.and(std::io::stderr.with_max_level(Level::WARN))
|
||
<span class="comment">// Write `INFO` to `stdout`.
|
||
</span>.and(std::io::stdout
|
||
.with_max_level(Level::INFO)
|
||
.with_min_level(Level::INFO)
|
||
);
|
||
|
||
tracing_subscriber::fmt().with_writer(mk_writer).init();</code></pre></div>
|
||
</div></details><details class="toggle method-toggle" open><summary><section id="method.or_else" class="method"><a class="src rightside" href="../../../src/tracing_subscriber/fmt/writer.rs.html#483-490">source</a><h4 class="code-header">fn <a href="#method.or_else" class="fn">or_else</a><W, B>(self, other: B) -> <a class="struct" href="struct.OrElse.html" title="struct tracing_subscriber::fmt::writer::OrElse">OrElse</a><Self, B><div class="where">where
|
||
Self: <a class="trait" href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter">MakeWriter</a><'a, Writer = <a class="type" href="type.OptionalWriter.html" title="type tracing_subscriber::fmt::writer::OptionalWriter">OptionalWriter</a><W>> + <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,
|
||
B: <a class="trait" href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter">MakeWriter</a><'a> + <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,
|
||
W: <a class="trait" href="https://doc.rust-lang.org/1.76.0/std/io/trait.Write.html" title="trait std::io::Write">Write</a>,</div></h4></section></summary><div class="docblock"><p>Combines <code>self</code> with another type implementing <a href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a>, returning
|
||
a new <a href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a> that calls <code>other</code>’s <a href="../trait.MakeWriter.html#tymethod.make_writer" title="method tracing_subscriber::fmt::MakeWriter::make_writer"><code>make_writer</code></a> if <code>self</code>’s
|
||
<code>make_writer</code> returns <a href="enum.EitherWriter.html#method.none" title="associated function tracing_subscriber::fmt::writer::EitherWriter::none"><code>OptionalWriter::none</code></a>.</p>
|
||
<h5 id="examples-4"><a href="#examples-4">Examples</a></h5>
|
||
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tracing::Level;
|
||
<span class="kw">use </span>tracing_subscriber::fmt::writer::MakeWriterExt;
|
||
|
||
<span class="comment">// Produces a writer that writes to `stderr` if the level is >= WARN,
|
||
// or returns `OptionalWriter::none()` otherwise.
|
||
</span><span class="kw">let </span>stderr = std::io::stderr.with_max_level(Level::WARN);
|
||
|
||
<span class="comment">// If the `stderr` `MakeWriter` is disabled by the max level filter,
|
||
// write to stdout instead:
|
||
</span><span class="kw">let </span>mk_writer = stderr.or_else(std::io::stdout);
|
||
|
||
tracing_subscriber::fmt().with_writer(mk_writer).init();</code></pre></div>
|
||
</div></details></div><h2 id="implementors" class="section-header">Implementors<a href="#implementors" class="anchor">§</a></h2><div id="implementors-list"><section id="impl-MakeWriterExt%3C'a%3E-for-M" class="impl"><a class="src rightside" href="../../../src/tracing_subscriber/fmt/writer.rs.html#1201">source</a><a href="#impl-MakeWriterExt%3C'a%3E-for-M" class="anchor">§</a><h3 class="code-header">impl<'a, M> <a class="trait" href="trait.MakeWriterExt.html" title="trait tracing_subscriber::fmt::writer::MakeWriterExt">MakeWriterExt</a><'a> for M<div class="where">where
|
||
M: <a class="trait" href="../trait.MakeWriter.html" title="trait tracing_subscriber::fmt::MakeWriter">MakeWriter</a><'a>,</div></h3></section></div><script src="../../../trait.impl/tracing_subscriber/fmt/writer/trait.MakeWriterExt.js" async></script><script type="text/json" id="notable-traits-data">{"Tee<Self, B>":"<h3>Notable traits for <code><a class=\"struct\" href=\"struct.Tee.html\" title=\"struct tracing_subscriber::fmt::writer::Tee\">Tee</a><A, B></code></h3><pre><code><div class=\"where\">impl<A, B> <a class=\"trait\" href=\"https://doc.rust-lang.org/1.76.0/std/io/trait.Write.html\" title=\"trait std::io::Write\">Write</a> for <a class=\"struct\" href=\"struct.Tee.html\" title=\"struct tracing_subscriber::fmt::writer::Tee\">Tee</a><A, B><div class=\"where\">where\n A: <a class=\"trait\" href=\"https://doc.rust-lang.org/1.76.0/std/io/trait.Write.html\" title=\"trait std::io::Write\">Write</a>,\n B: <a class=\"trait\" href=\"https://doc.rust-lang.org/1.76.0/std/io/trait.Write.html\" title=\"trait std::io::Write\">Write</a>,</div></div>"}</script></section></div></main></body></html> |