187 lines
7.1 KiB
Plaintext
187 lines
7.1 KiB
Plaintext
<!DOCTYPE html>
|
|
<html>
|
|
<head>
|
|
<meta http-eqiv="content-type" content="text/html;charset=utf-8">
|
|
<title>Go by Example: Signals</title>
|
|
<link rel=stylesheet href="site.css">
|
|
</head>
|
|
<script type="text/javascript">
|
|
if (window.location.host == "gobyexample.com") {
|
|
var _gaq = _gaq || [];
|
|
_gaq.push(['_setAccount', 'UA-34996217-1']);
|
|
_gaq.push(['_trackPageview']);
|
|
(function() {
|
|
var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
|
|
ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
|
|
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
|
|
})();
|
|
}
|
|
</script>
|
|
<body>
|
|
<div class="example" id="signals">
|
|
<h2><a href="./">Go by Example</a>: Signals</h2>
|
|
|
|
<table>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>Sometimes we’d like our Go programs to intelligently
|
|
handle <a href="http://en.wikipedia.org/wiki/Unix_signal">Unix signals</a>.
|
|
For example, we might want a server to gracefully
|
|
shutdown when it receives a <code>SIGTERM</code>, or a command-line
|
|
tool to stop processing input if it receives a <code>SIGINT</code>.
|
|
Here’s how to handle signals in Go with channels.</p>
|
|
|
|
</td>
|
|
<td class="code empty leading">
|
|
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
<a href="http://play.golang.org/p/BlkqAtKsxo"><img title="Run code" src="play.png" class="run" /></a>
|
|
<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre><span class="kn">import</span> <span class="s">"fmt"</span>
|
|
<span class="kn">import</span> <span class="s">"os"</span>
|
|
<span class="kn">import</span> <span class="s">"os/signal"</span>
|
|
<span class="kn">import</span> <span class="s">"syscall"</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>Go signal notification works by sending <code>os.Signal</code>
|
|
values on a channel. We’ll create a channel to
|
|
receive these notifications (we’ll also make one to
|
|
notify us when the program can exit).</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre> <span class="nx">sigs</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="nx">os</span><span class="p">.</span><span class="nx">Signal</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>
|
|
<span class="nx">done</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="kt">bool</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p><code>signal.Notify</code> registers the given channel to
|
|
receive notifications of the specified signals.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre> <span class="nx">signal</span><span class="p">.</span><span class="nx">Notify</span><span class="p">(</span><span class="nx">sigs</span><span class="p">,</span> <span class="nx">syscall</span><span class="p">.</span><span class="nx">SIGINT</span><span class="p">,</span> <span class="nx">syscall</span><span class="p">.</span><span class="nx">SIGTERM</span><span class="p">)</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>This goroutine executes a blocking receive for
|
|
signals. When it gets one it’ll print it out
|
|
and then notify the program that it can finish.</p>
|
|
|
|
</td>
|
|
<td class="code leading">
|
|
|
|
<div class="highlight"><pre> <span class="k">go</span> <span class="kd">func</span><span class="p">()</span> <span class="p">{</span>
|
|
<span class="nx">sig</span> <span class="o">:=</span> <span class="o"><-</span><span class="nx">sigs</span>
|
|
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">()</span>
|
|
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">sig</span><span class="p">)</span>
|
|
<span class="nx">done</span> <span class="o"><-</span> <span class="kc">true</span>
|
|
<span class="p">}()</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>The program will wait here until it gets the
|
|
expected signal (as indicated by the goroutine
|
|
above sending a value on <code>done</code>) and then exit.</p>
|
|
|
|
</td>
|
|
<td class="code">
|
|
|
|
<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"awaiting signal"</span><span class="p">)</span>
|
|
<span class="o"><-</span><span class="nx">done</span>
|
|
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"exiting"</span><span class="p">)</span>
|
|
<span class="p">}</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table>
|
|
|
|
<tr>
|
|
<td class="docs">
|
|
<p>When we run this program it will block waiting for a
|
|
signal. By typing <code>ctrl-C</code> (which the
|
|
terminal shows as <code>^C</code>) we can send a <code>SIGINT</code> signal,
|
|
causing the program to print <code>interrupt</code> and then exit.</p>
|
|
|
|
</td>
|
|
<td class="code">
|
|
|
|
<div class="highlight"><pre><span class="gp">$</span> go run signals.go
|
|
<span class="go">awaiting signal</span>
|
|
<span class="go">^C</span>
|
|
<span class="go">interrupt</span>
|
|
<span class="go">exiting</span>
|
|
</pre></div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
|
|
<p class="next">
|
|
Next example: <a href="exit">Exit</a>.
|
|
</p>
|
|
|
|
<p class="footer">
|
|
by <a href="https://twitter.com/mmcgrana">@mmcgrana</a> | <a href="mailto:mmcgrana@gmail.com">feedback</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/signals">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
|
|
</p>
|
|
</div>
|
|
</body>
|
|
</html>
|