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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 `alarm` mod in crate `nix`."><meta name="keywords" content="rust, rustlang, rust-lang, alarm"><title>nix::unistd::alarm - 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="../../../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='../../../nix/index.html'><div class='logo-container'><img src='../../../rust-logo.png' alt='logo'></div></a><p class='location'>Module alarm</p><div class="sidebar-elems"><div class="block items"><ul><li><a href="#functions">Functions</a></li></ul></div><p class='location'><a href='../../index.html'>nix</a>::<wbr><a href='../index.html'>unistd</a></p><script>window.sidebarCurrent = {name: 'alarm', ty: 'mod', 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/nix/unistd.rs.html#1509-1586' title='goto source code'>[src]</a></span><span class='in-band'>Module <a href='../../index.html'>nix</a>::<wbr><a href='../index.html'>unistd</a>::<wbr><a class="mod" href=''>alarm</a></span></h1><div class='docblock'><p>Alarm signal scheduling.</p>
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<p>Scheduling an alarm will trigger a <code>SIGALRM</code> signal when the time has
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elapsed, which has to be caught, because the default action for the
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signal is to terminate the program. This signal also can't be ignored
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because the system calls like <code>pause</code> will not be interrupted, see the
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second example below.</p>
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<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
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<p>Canceling an alarm:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered">
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<span class="kw">use</span> <span class="ident">nix</span>::<span class="ident">unistd</span>::<span class="ident">alarm</span>;
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<span class="comment">// Set an alarm for 60 seconds from now.</span>
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<span class="ident">alarm</span>::<span class="ident">set</span>(<span class="number">60</span>);
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<span class="comment">// Cancel the above set alarm, which returns the number of seconds left</span>
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<span class="comment">// of the previously set alarm.</span>
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">alarm</span>::<span class="ident">cancel</span>(), <span class="prelude-val">Some</span>(<span class="number">60</span>));</pre></div>
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<p>Scheduling an alarm and waiting for the signal:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered">
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<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">time</span>::{<span class="ident">Duration</span>, <span class="ident">Instant</span>};
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<span class="kw">use</span> <span class="ident">nix</span>::<span class="ident">unistd</span>::{<span class="ident">alarm</span>, <span class="ident">pause</span>};
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<span class="kw">use</span> <span class="ident">nix</span>::<span class="ident">sys</span>::<span class="ident">signal</span>::<span class="kw-2">*</span>;
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<span class="comment">// We need to setup an empty signal handler to catch the alarm signal,</span>
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<span class="comment">// otherwise the program will be terminated once the signal is delivered.</span>
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<span class="kw">extern</span> <span class="kw">fn</span> <span class="ident">signal_handler</span>(<span class="kw">_</span>: <span class="ident">nix</span>::<span class="ident">libc</span>::<span class="ident">c_int</span>) { }
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<span class="kw">unsafe</span> { <span class="ident">sigaction</span>(<span class="ident">Signal</span>::<span class="ident">SIGALRM</span>, <span class="kw-2">&</span><span class="ident">SigAction</span>::<span class="ident">new</span>(<span class="ident">SigHandler</span>::<span class="ident">Handler</span>(<span class="ident">signal_handler</span>), <span class="ident">SaFlags</span>::<span class="ident">empty</span>(), <span class="ident">SigSet</span>::<span class="ident">empty</span>())); }
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<span class="comment">// Set an alarm for 1 second from now.</span>
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<span class="ident">alarm</span>::<span class="ident">set</span>(<span class="number">1</span>);
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<span class="kw">let</span> <span class="ident">start</span> <span class="op">=</span> <span class="ident">Instant</span>::<span class="ident">now</span>();
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<span class="comment">// Pause the process until the alarm signal is received.</span>
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<span class="ident">pause</span>();
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<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">start</span>.<span class="ident">elapsed</span>() <span class="op">></span><span class="op">=</span> <span class="ident">Duration</span>::<span class="ident">from_secs</span>(<span class="number">1</span>));</pre></div>
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<h1 id="references" class="section-header"><a href="#references">References</a></h1>
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<p>See also <a href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/alarm.html">alarm(2)</a>.</p>
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</div><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.cancel.html" title='nix::unistd::alarm::cancel fn'>cancel</a></td><td class='docblock-short'><p>Cancel an previously set alarm signal.</p>
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</td></tr><tr class='module-item'><td><a class="fn" href="fn.set.html" title='nix::unistd::alarm::set fn'>set</a></td><td class='docblock-short'><p>Schedule an alarm signal.</p>
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