| <!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="Alarm signal scheduling."><meta name="keywords" content="rust, rustlang, rust-lang, alarm"><title>nix::unistd::alarm - 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="../../../nix/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="../../../nix/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a><h2 class="location"><a href="#">Module alarm</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">nix</a>::<wbr><a href="../index.html">unistd</a>::<wbr><a class="mod" href="#">alarm</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/nix/unistd.rs.html#1753">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>Alarm signal scheduling.</p> |
| <p>Scheduling an alarm will trigger a <code>SIGALRM</code> signal when the time has |
| elapsed, which has to be caught, because the default action for the |
| signal is to terminate the program. This signal also can’t be ignored |
| because the system calls like <code>pause</code> will not be interrupted, see the |
| second example below.</p> |
| <h2 id="examples"><a href="#examples">Examples</a></h2> |
| <p>Canceling an alarm:</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>nix::unistd::alarm; |
| |
| <span class="comment">// Set an alarm for 60 seconds from now. |
| </span>alarm::set(<span class="number">60</span>); |
| |
| <span class="comment">// Cancel the above set alarm, which returns the number of seconds left |
| // of the previously set alarm. |
| </span><span class="macro">assert_eq!</span>(alarm::cancel(), <span class="prelude-val">Some</span>(<span class="number">60</span>));</code></pre></div> |
| <p>Scheduling an alarm and waiting for the signal:</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::time::{Duration, Instant}; |
| |
| <span class="kw">use </span>nix::unistd::{alarm, pause}; |
| <span class="kw">use </span>nix::sys::signal::<span class="kw-2">*</span>; |
| |
| <span class="comment">// We need to setup an empty signal handler to catch the alarm signal, |
| // otherwise the program will be terminated once the signal is delivered. |
| </span><span class="kw">extern fn </span>signal_handler(<span class="kw">_</span>: nix::libc::c_int) { } |
| <span class="kw">let </span>sa = SigAction::new( |
| SigHandler::Handler(signal_handler), |
| SaFlags::SA_RESTART, |
| SigSet::empty() |
| ); |
| <span class="kw">unsafe </span>{ |
| sigaction(Signal::SIGALRM, <span class="kw-2">&</span>sa); |
| } |
| |
| <span class="kw">let </span>start = Instant::now(); |
| |
| <span class="comment">// Set an alarm for 1 second from now. |
| </span>alarm::set(<span class="number">1</span>); |
| |
| <span class="comment">// Pause the process until the alarm signal is received. |
| </span><span class="kw">let </span><span class="kw-2">mut </span>sigset = SigSet::empty(); |
| sigset.add(Signal::SIGALRM); |
| sigset.wait(); |
| |
| <span class="macro">assert!</span>(start.elapsed() >= Duration::from_secs(<span class="number">1</span>));</code></pre></div> |
| <h2 id="references"><a href="#references">References</a></h2> |
| <p>See also <a href="https://pubs.opengroup.org/onlinepubs/9699919799/functions/alarm.html">alarm(2)</a>.</p> |
| </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.cancel.html" title="nix::unistd::alarm::cancel fn">cancel</a></div><div class="item-right docblock-short">Cancel an previously set alarm signal.</div></div><div class="item-row"><div class="item-left module-item"><a class="fn" href="fn.set.html" title="nix::unistd::alarm::set fn">set</a></div><div class="item-right docblock-short">Schedule an alarm signal.</div></div></div></section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="nix" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
