| <!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="Module for actions setting flags."><meta name="keywords" content="rust, rustlang, rust-lang, flag"><title>signal_hook::flag - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc mod"><!--[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="sidebar-logo" href="../../signal_hook/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a><h2></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../../signal_hook/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a><h2 class="location"><a href="#">Module flag</a></h2><div class="sidebar-elems"><section><ul class="block"><li><a href="#functions">Functions</a></li></ul></section></div></nav><main><div class="width-limiter"><nav class="sub"><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1 class="fqn">Module <a href="../index.html">signal_hook</a>::<wbr><a class="mod" href="#">flag</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../../clipboard.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="srclink" href="../../src/signal_hook/flag.rs.html#1-214">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Module for actions setting flags.</p> |
| <p>This contains helper functions to set flags whenever a signal happens. The flags are atomic |
| bools or numbers and the library manipulates them with the <code>SeqCst</code> ordering, in case someone |
| cares about relative order to some <em>other</em> atomic variables. If you don’t care about the |
| relative order, you are free to use <code>Ordering::Relaxed</code> when reading and resetting the flags.</p> |
| <h2 id="when-to-use"><a href="#when-to-use">When to use</a></h2> |
| <p>The flags in this module allow for polling if a signal arrived since the previous poll. The do |
| not allow blocking until something arrives.</p> |
| <p>Therefore, the natural way to use them is in applications that have some kind of iterative work |
| with both some upper and lower time limit on one iteration. If one iteration could block for |
| arbitrary time, the handling of the signal would be postponed for a long time. If the iteration |
| didn’t block at all, the checking for the signal would turn into a busy-loop.</p> |
| <p>If what you need is blocking until a signal comes, you might find better tools in the |
| <a href="../pipe/"><code>pipe</code></a> and <a href="../iterator/"><code>iterator</code></a> modules.</p> |
| <h2 id="examples"><a href="#examples">Examples</a></h2> |
| <p>Doing something until terminated. This also knows by which signal it was terminated. In case |
| multiple termination signals arrive before it is handled, it recognizes the last one.</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">extern crate </span>signal_hook; |
| |
| <span class="kw">use </span>std::io::Error; |
| <span class="kw">use </span>std::sync::Arc; |
| <span class="kw">use </span>std::sync::atomic::{AtomicUsize, Ordering}; |
| |
| <span class="kw">use </span>signal_hook::flag <span class="kw">as </span>signal_flag; |
| |
| <span class="kw">fn </span>main() -> <span class="prelude-ty">Result</span><(), Error> { |
| <span class="kw">let </span>term = Arc::new(AtomicUsize::new(<span class="number">0</span>)); |
| <span class="kw">const </span>SIGTERM: usize = signal_hook::SIGTERM <span class="kw">as </span>usize; |
| <span class="kw">const </span>SIGINT: usize = signal_hook::SIGINT <span class="kw">as </span>usize; |
| <span class="kw">const </span>SIGQUIT: usize = signal_hook::SIGQUIT <span class="kw">as </span>usize; |
| signal_flag::register_usize(signal_hook::SIGTERM, Arc::clone(<span class="kw-2">&</span>term), SIGTERM)<span class="question-mark">?</span>; |
| signal_flag::register_usize(signal_hook::SIGINT, Arc::clone(<span class="kw-2">&</span>term), SIGINT)<span class="question-mark">?</span>; |
| signal_flag::register_usize(signal_hook::SIGQUIT, Arc::clone(<span class="kw-2">&</span>term), SIGQUIT)<span class="question-mark">?</span>; |
| |
| <span class="kw">loop </span>{ |
| <span class="kw">match </span>term.load(Ordering::Relaxed) { |
| <span class="number">0 </span>=> { |
| <span class="comment">// Do some useful stuff here |
| </span>} |
| SIGTERM => { |
| <span class="macro">eprintln!</span>(<span class="string">"Terminating on the TERM signal"</span>); |
| <span class="kw">break</span>; |
| } |
| SIGINT => { |
| <span class="macro">eprintln!</span>(<span class="string">"Terminating on the INT signal"</span>); |
| <span class="kw">break</span>; |
| } |
| SIGQUIT => { |
| <span class="macro">eprintln!</span>(<span class="string">"Terminating on the QUIT signal"</span>); |
| <span class="kw">break</span>; |
| } |
| <span class="kw">_ </span>=> <span class="macro">unreachable!</span>(), |
| } |
| } |
| |
| <span class="prelude-val">Ok</span>(()) |
| }</code></pre></div> |
| <p>Sending a signal to self and seeing it arrived (not of a practical usage on itself):</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">extern crate </span>libc; |
| <span class="kw">extern crate </span>signal_hook; |
| |
| <span class="kw">use </span>std::io::Error; |
| <span class="kw">use </span>std::sync::Arc; |
| <span class="kw">use </span>std::sync::atomic::{AtomicBool, Ordering}; |
| <span class="kw">use </span>std::thread; |
| <span class="kw">use </span>std::time::Duration; |
| |
| <span class="kw">fn </span>main() -> <span class="prelude-ty">Result</span><(), Error> { |
| <span class="kw">let </span>got = Arc::new(AtomicBool::new(<span class="bool-val">false</span>)); |
| signal_hook::flag::register(signal_hook::SIGUSR1, Arc::clone(<span class="kw-2">&</span>got))<span class="question-mark">?</span>; |
| <span class="kw">unsafe </span>{ |
| libc::raise(signal_hook::SIGUSR1); |
| } |
| <span class="comment">// A sleep here, because it could run the signal handler in another thread and we may not |
| // see the flag right away. This is still a hack and not guaranteed to work, it is just an |
| // example! |
| </span>thread::sleep(Duration::from_secs(<span class="number">1</span>)); |
| <span class="macro">assert!</span>(got.load(Ordering::Relaxed)); |
| <span class="prelude-val">Ok</span>(()) |
| }</code></pre></div> |
| <p>Reloading a configuration on <code>SIGHUP</code> (which is a common behaviour of many UNIX daemons, |
| together with reopening the log file).</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">extern crate </span>signal_hook; |
| |
| <span class="kw">use </span>std::io::Error; |
| <span class="kw">use </span>std::sync::Arc; |
| <span class="kw">use </span>std::sync::atomic::{AtomicBool, Ordering}; |
| |
| <span class="kw">use </span>signal_hook::flag <span class="kw">as </span>signal_flag; |
| |
| <span class="kw">fn </span>main() -> <span class="prelude-ty">Result</span><(), Error> { |
| <span class="comment">// We start with true, to load the configuration in the very first iteration too. |
| </span><span class="kw">let </span>reload = Arc::new(AtomicBool::new(<span class="bool-val">true</span>)); |
| <span class="kw">let </span>term = Arc::new(AtomicBool::new(<span class="bool-val">false</span>)); |
| signal_flag::register(signal_hook::SIGHUP, Arc::clone(<span class="kw-2">&</span>reload))<span class="question-mark">?</span>; |
| signal_flag::register(signal_hook::SIGINT, Arc::clone(<span class="kw-2">&</span>term))<span class="question-mark">?</span>; |
| signal_flag::register(signal_hook::SIGTERM, Arc::clone(<span class="kw-2">&</span>term))<span class="question-mark">?</span>; |
| signal_flag::register(signal_hook::SIGQUIT, Arc::clone(<span class="kw-2">&</span>term))<span class="question-mark">?</span>; |
| <span class="kw">while </span>!term.load(Ordering::Relaxed) { |
| <span class="comment">// Using swap here, not load, to reset it back to false once it is reloaded. |
| </span><span class="kw">if </span>reload.swap(<span class="bool-val">false</span>, Ordering::Relaxed) { |
| <span class="comment">// Reload the config here |
| </span>} |
| <span class="comment">// Serve one request |
| </span>} |
| <span class="prelude-val">Ok</span>(()) |
| }</code></pre></div> |
| </div></details><h2 id="functions" class="small-section-header"><a href="#functions">Functions</a></h2><div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="fn" href="fn.register.html" title="signal_hook::flag::register fn">register</a></div><div class="item-right docblock-short">Registers an action to set the flag to <code>true</code> whenever the given signal arrives.</div></div><div class="item-row"><div class="item-left module-item"><a class="fn" href="fn.register_usize.html" title="signal_hook::flag::register_usize fn">register_usize</a></div><div class="item-right docblock-short">Registers an action to set the flag to the given value whenever the signal arrives.</div></div></div></section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="signal_hook" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
