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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 219</span><hr><div class="refentry"><a name="sd_event_get_fd"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_event_get_fd — Obtain a file descriptor to poll for event loop events</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <systemd/sd-bus.h></pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_event_get_fd</b>(</code></td><td>sd_bus *<var class="pdparam">event</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm139634046162512"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_event_get_fd()</code> returns the file
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descriptor that the event loop object returned by the
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<a href="sd_event_new.html"><span class="citerefentry"><span class="refentrytitle">sd_event_new</span>(3)</span></a>
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function uses to wait for events. This file descriptor can be
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polled for events. This makes it possible to embed the
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<a href="sd-event.html"><span class="citerefentry"><span class="refentrytitle">sd-event</span>(3)</span></a>
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event loop inside of another event loop.</p></div><div class="refsect1"><a name="idm139634046186672"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>On success, <code class="function">sd_event_get_fd()</code> returns a
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non-negative integer. On failure, it returns a negative
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errno-style error code.</p></div><div class="refsect1"><a name="idm139634042349936"></a><h2 id="Errors">Errors<a class="headerlink" title="Permalink to this headline" href="#Errors">¶</a></h2><p>Returned errors may indicate the following problems:</p><div class="variablelist"><dl class="variablelist"><dt id="-EINVAL"><span class="term"><code class="constant">-EINVAL</code></span><a class="headerlink" title="Permalink to this term" href="#-EINVAL">¶</a></dt><dd><p><em class="parameter"><code>event</code></em> is not a valid
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pointer to an <span class="structname">sd_event</span> structure.
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</p></dd><dt id="-ECHILD"><span class="term"><code class="constant">-ECHILD</code></span><a class="headerlink" title="Permalink to this term" href="#-ECHILD">¶</a></dt><dd><p>The event loop has been created in a different process.</p></dd></dl></div></div><div class="refsect1"><a name="idm139634042344432"></a><h2 id="Examples">Examples<a class="headerlink" title="Permalink to this headline" href="#Examples">¶</a></h2><div class="example"><a name="idm139634042343760"></a><p class="title"><b>Example 1. Integration in glib event loop</b></p><div class="example-contents"><pre class="programlisting">/***
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Copyright 2014 Tom Gundersen
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Permission is hereby granted, free of charge, to any person
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obtaining a copy of this software and associated documentation files
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(the "Software"), to deal in the Software without restriction,
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including without limitation the rights to use, copy, modify, merge,
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publish, distribute, sublicense, and/or sell copies of the Software,
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and to permit persons to whom the Software is furnished to do so,
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subject to the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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***/
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#include <stdlib.h>
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typedef struct SDEventSource {
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GSource source;
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GPollFD pollfd;
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sd_event *event;
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} SDEventSource;
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static gboolean event_prepare(GSource *source, gint *timeout_) {
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return sd_event_prepare(((SDEventSource *)source)->event) > 0;
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}
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static gboolean event_check(GSource *source) {
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return sd_event_wait(((SDEventSource *)source)->event, 0) > 0;
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}
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static gboolean event_dispatch(GSource *source, GSourceFunc callback, gpointer user_data) {
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return sd_event_dispatch(((SDEventSource *)source)->event) > 0;
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}
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static void event_finalize(GSource *source) {
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sd_event_unref(((SDEventSource *)source)->event);
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}
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static GSourceFuncs event_funcs = {
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.prepare = event_prepare,
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.check = event_check,
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.dispatch = event_dispatch,
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.finalize = event_finalize,
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};
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GSource *g_sd_event_create_source(sd_event *event) {
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SDEventSource *source;
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source = (SDEventSource *)g_source_new(&event_funcs, sizeof(SDEventSource));
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source->event = sd_event_ref(event);
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source->pollfd.fd = sd_event_get_fd(event);
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source->pollfd.events = G_IO_IN | G_IO_HUP | G_IO_ERR;
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g_source_add_poll((GSource *)source, &source->pollfd);
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return (GSource *)source;
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}
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</pre></div></div><br class="example-break"></div><div class="refsect1"><a name="idm139634042341616"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p><code class="function">sd_event_get_fd()</code> is available as a
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shared library, which can be compiled and linked to with the
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<code class="constant">libsystemd</code> <a href="http://linux.die.net/man/1/pkg-config"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
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file.</p></div><div class="refsect1"><a name="idm139634042338160"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
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<a href="sd-event.html"><span class="citerefentry"><span class="refentrytitle">sd-event</span>(3)</span></a>,
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<a href="sd_event_new.html"><span class="citerefentry"><span class="refentrytitle">sd_event_new</span>(3)</span></a>,
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<a href="sd_event_ref.html"><span class="citerefentry"><span class="refentrytitle">sd_event_ref</span>(3)</span></a>
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</p></div></div></body></html>
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