| <!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="Library for easier and safe Unix signal handling"><meta name="keywords" content="rust, rustlang, rust-lang, signal_hook"><title>signal_hook - 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="../crates.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 crate"><!--[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="#">Crate signal_hook</a></h2><div class="sidebar-elems"><ul class="block"><li class="version">Version 0.1.17</li><li><a id="all-types" href="all.html">All Items</a></li></ul><section><ul class="block"><li><a href="#modules">Modules</a></li><li><a href="#structs">Structs</a></li><li><a href="#constants">Constants</a></li><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">Crate <a class="mod" href="#">signal_hook</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/lib.rs.html#1-190">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>Library for easier and safe Unix signal handling</p> |
| <p>Unix signals are inherently hard to handle correctly, for several reasons:</p> |
| <ul> |
| <li>They are a global resource. If a library wants to set its own signal handlers, it risks |
| disturbing some other library. It is possible to chain the previous signal handler, but then |
| it is impossible to remove the old signal handlers from the chains in any practical manner.</li> |
| <li>They can be called from whatever thread, requiring synchronization. Also, as they can |
| interrupt a thread at any time, making most handling race-prone.</li> |
| <li>According to the POSIX standard, the set of functions one may call inside a signal handler is |
| limited to very few of them. To highlight, mutexes (or other locking mechanisms) and memory |
| allocation and deallocation is <em>not</em> allowed.</li> |
| </ul> |
| <p>This library aims to solve some of the problems. It provides a global registry of actions |
| performed on arrival of signals. It is possible to register multiple actions for the same |
| signal and it is possible to remove the actions later on. If there was a previous signal |
| handler when the first action for a signal is registered, it is chained (but the original one |
| can’t be removed).</p> |
| <p>The main function of the library is <a href="fn.register.html"><code>register</code></a>.</p> |
| <p>It also offers several common actions one might want to register, implemented in the correct |
| way. They are scattered through submodules and have the same limitations and characteristics as |
| the <a href="fn.register.html"><code>register</code></a> function. Generally, they work to postpone the action taken |
| outside of the signal handler, where the full freedom and power of rust is available.</p> |
| <p>Unlike other Rust libraries for signal handling, this should be flexible enough to handle all |
| the common and useful patterns.</p> |
| <p>The library avoids all the newer fancy signal-handling routines. These generally have two |
| downsides:</p> |
| <ul> |
| <li>They are not fully portable, therefore the library would have to contain <em>both</em> the |
| implementation using the basic routines and the fancy ones. As signal handling is not on the |
| hot path of most programs, this would not bring any actual benefit.</li> |
| <li>The other routines require that the given signal is masked in all application’s threads. As |
| the signals are not masked by default and a new thread inherits the signal mask of its |
| parent, it is possible to guarantee such global mask by masking them before any threads |
| start. While this is possible for an application developer to do, it is not possible for a |
| a library.</li> |
| </ul> |
| <h2 id="warning"><a href="#warning">Warning</a></h2> |
| <p>Even with this library, you should thread with care. It does not eliminate all the problems |
| mentioned above.</p> |
| <p>Also, note that the OS may collate multiple instances of the same signal into just one call of |
| the signal handler. Furthermore, some abstractions implemented here also naturally collate |
| multiple instances of the same signal. The general guarantee is, if there was at least one |
| signal of the given number delivered, an action will be taken, but it is not specified how many |
| times ‒ signals work mostly as kind of „wake up now“ nudge, if the application is slow to wake |
| up, it may be nudged multiple times before it does so.</p> |
| <h2 id="signal-limitations"><a href="#signal-limitations">Signal limitations</a></h2> |
| <p>OS limits still apply ‒ it is not possible to redefine certain signals (eg. <code>SIGKILL</code> or |
| <code>SIGSTOP</code>) and it is probably a <em>very</em> stupid idea to touch certain other ones (<code>SIGSEGV</code>, |
| <code>SIGFPE</code>, <code>SIGILL</code>). Therefore, this library will panic if any attempt at manipulating these is |
| made. There are some use cases for redefining the latter ones, but these are not well served by |
| this library and you really <em>really</em> have to know what you’re doing and are generally on your |
| own doing that.</p> |
| <h2 id="signal-masks"><a href="#signal-masks">Signal masks</a></h2> |
| <p>As the library uses <code>sigaction</code> under the hood, signal masking works as expected (eg. with |
| <code>pthread_sigmask</code>). This means, signals will <em>not</em> be delivered if the signal is masked in all |
| program’s threads.</p> |
| <p>By the way, if you do want to modify the signal mask (or do other Unix-specific magic), the |
| <a href="https://crates.io/crates/nix">nix</a> crate offers safe interface to many low-level functions, |
| including |
| <a href="https://docs.rs/nix/0.11.0/nix/sys/signal/fn.pthread_sigmask.html"><code>pthread_sigmask</code></a>.</p> |
| <h2 id="portability"><a href="#portability">Portability</a></h2> |
| <p>It should work on any POSIX.1-2001 system, which are all the major big OSes with the notable |
| exception of Windows.</p> |
| <p>Non-standard signals are also supported. Pass the signal value directly from <code>libc</code> or use |
| the numeric value directly.</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::sync::Arc; |
| <span class="kw">use </span>std::sync::atomic::{AtomicBool}; |
| <span class="kw">let </span>term = Arc::new(AtomicBool::new(<span class="bool-val">false</span>)); |
| <span class="kw">let _ </span>= signal_hook::flag::register(libc::SIGINT, Arc::clone(<span class="kw-2">&</span>term));</code></pre></div> |
| <p>This crate includes a limited support for Windows, based on <code>signal</code>/<code>raise</code> in the CRT. |
| There are differences in both API and behavior:</p> |
| <ul> |
| <li><code>iterator</code> and <code>pipe</code> are not yet implemented.</li> |
| <li>We have only a few signals: <code>SIGABRT</code>, <code>SIGABRT_COMPAT</code>, <code>SIGBREAK</code>, |
| <code>SIGFPE</code>, <code>SIGILL</code>, <code>SIGINT</code>, <code>SIGSEGV</code> and <code>SIGTERM</code>.</li> |
| <li>Due to lack of signal blocking, there’s a race condition. |
| After the call to <code>signal</code>, there’s a moment where we miss a signal. |
| That means when you register a handler, there may be a signal which invokes |
| neither the default handler or the handler you register.</li> |
| <li>Handlers registered by <code>signal</code> in Windows are cleared on first signal. |
| To match behavior in other platforms, we re-register the handler each time the handler is |
| called, but there’s a moment where we miss a handler. |
| That means when you receive two signals in a row, there may be a signal which invokes |
| the default handler, nevertheless you certainly have registered the handler.</li> |
| </ul> |
| <p>Moreover, signals won’t work as you expected. <code>SIGTERM</code> isn’t actually used and |
| not all <code>Ctrl-C</code>s are turned into <code>SIGINT</code>.</p> |
| <p>Patches to improve Windows support in this library are welcome.</p> |
| <h2 id="examples"><a href="#examples">Examples</a></h2> |
| <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">fn </span>main() -> <span class="prelude-ty">Result</span><(), Error> { |
| <span class="kw">let </span>term = Arc::new(AtomicBool::new(<span class="bool-val">false</span>)); |
| signal_hook::flag::register(signal_hook::SIGTERM, 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">// Do some time-limited stuff here |
| // (if this could block forever, then there's no guarantee the signal will have any |
| // effect). |
| </span>} |
| <span class="prelude-val">Ok</span>(()) |
| }</code></pre></div> |
| <h2 id="features"><a href="#features">Features</a></h2> |
| <ul> |
| <li><code>mio-support</code>: The <a href="iterator/struct.Signals.html"><code>Signals</code> iterator</a> becomes pluggable into |
| mio 0.6.</li> |
| <li><code>mio-0_7-support</code>: The <a href="iterator/struct.Signals.html"><code>Signals</code> iterator</a> becomes pluggable into |
| mio 0.7.</li> |
| <li><code>tokio-support</code>: The <a href="iterator/struct.Signals.html"><code>Signals</code></a> can be turned into |
| <a href="iterator/struct.Async.html"><code>Async</code></a>, which provides a <code>Stream</code> interface for integration in |
| the asynchronous world.</li> |
| </ul> |
| </div></details><h2 id="modules" class="small-section-header"><a href="#modules">Modules</a></h2><div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="mod" href="cleanup/index.html" title="signal_hook::cleanup mod">cleanup</a></div><div class="item-right docblock-short">Cleaning up signals.</div></div><div class="item-row"><div class="item-left module-item"><a class="mod" href="flag/index.html" title="signal_hook::flag mod">flag</a></div><div class="item-right docblock-short">Module for actions setting flags.</div></div><div class="item-row"><div class="item-left module-item"><a class="mod" href="iterator/index.html" title="signal_hook::iterator mod">iterator</a></div><div class="item-right docblock-short">An iterator over incoming signals.</div></div><div class="item-row"><div class="item-left module-item"><a class="mod" href="pipe/index.html" title="signal_hook::pipe mod">pipe</a></div><div class="item-right docblock-short">Module with the self-pipe pattern.</div></div></div><h2 id="structs" class="small-section-header"><a href="#structs">Structs</a></h2><div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.SigId.html" title="signal_hook::SigId struct">SigId</a></div><div class="item-right docblock-short">An ID of registered action.</div></div></div><h2 id="constants" class="small-section-header"><a href="#constants">Constants</a></h2><div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.FORBIDDEN.html" title="signal_hook::FORBIDDEN constant">FORBIDDEN</a></div><div class="item-right docblock-short">List of forbidden signals.</div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGABRT.html" title="signal_hook::SIGABRT constant">SIGABRT</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGALRM.html" title="signal_hook::SIGALRM constant">SIGALRM</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGBUS.html" title="signal_hook::SIGBUS constant">SIGBUS</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGCHLD.html" title="signal_hook::SIGCHLD constant">SIGCHLD</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGCONT.html" title="signal_hook::SIGCONT constant">SIGCONT</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGFPE.html" title="signal_hook::SIGFPE constant">SIGFPE</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGHUP.html" title="signal_hook::SIGHUP constant">SIGHUP</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGILL.html" title="signal_hook::SIGILL constant">SIGILL</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGINT.html" title="signal_hook::SIGINT constant">SIGINT</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGIO.html" title="signal_hook::SIGIO constant">SIGIO</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGKILL.html" title="signal_hook::SIGKILL constant">SIGKILL</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGPIPE.html" title="signal_hook::SIGPIPE constant">SIGPIPE</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGPROF.html" title="signal_hook::SIGPROF constant">SIGPROF</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGQUIT.html" title="signal_hook::SIGQUIT constant">SIGQUIT</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGSEGV.html" title="signal_hook::SIGSEGV constant">SIGSEGV</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGSTOP.html" title="signal_hook::SIGSTOP constant">SIGSTOP</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGSYS.html" title="signal_hook::SIGSYS constant">SIGSYS</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGTERM.html" title="signal_hook::SIGTERM constant">SIGTERM</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGTRAP.html" title="signal_hook::SIGTRAP constant">SIGTRAP</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGUSR1.html" title="signal_hook::SIGUSR1 constant">SIGUSR1</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGUSR2.html" title="signal_hook::SIGUSR2 constant">SIGUSR2</a></div></div><div class="item-row"><div class="item-left module-item"><a class="constant" href="constant.SIGWINCH.html" title="signal_hook::SIGWINCH constant">SIGWINCH</a></div></div></div><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::register fn">register</a><sup title="unsafe function">⚠</sup></div><div class="item-right docblock-short">Registers an arbitrary action for the given signal.</div></div><div class="item-row"><div class="item-left module-item"><a class="fn" href="fn.unregister.html" title="signal_hook::unregister fn">unregister</a></div><div class="item-right docblock-short">Removes a previously installed action.</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> |
