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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_new"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_event_new, sd_event_default, sd_event_ref, sd_event_unref — Acquire and release an event loop object</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_new</b>(</code></td><td>sd_bus **<var class="pdparam">event</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><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_default</b>(</code></td><td>sd_bus **<var class="pdparam">event</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">sd_bus *<b class="fsfunc">sd_event_ref</b>(</code></td><td>sd_bus *<var class="pdparam">event</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">sd_bus *<b class="fsfunc">sd_event_unref</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="idm139650549886336"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_event_new()</code> allocates a new event
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loop object. The event loop object is returned in the
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<em class="parameter"><code>event</code></em> parameter. After use, drop
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the returned reference with
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<code class="function">sd_event_unref()</code>. When the last reference is
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dropped, the object is freed.</p><p><code class="function">sd_event_default()</code> acquires a reference
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to the default event loop object of the calling thread, possibly
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allocating a new object if no default event loop object has been
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allocated yet for the thread. After use, drop the returned
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reference with <code class="function">sd_event_unref()</code>. When the
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last reference is dropped, the event loop is freed. If this
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function is called while the object returned from a previous call
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from the same thread is still referenced, the same object is
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returned again, but the reference is increased by one. It is
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recommended to use this call instead of
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<code class="function">sd_event_new()</code> in order to share event loop
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objects between various components that are dispatched in the same
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thread. All threads have exactly either zero or one default event loop
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objects associated, but never more.</p><p><code class="function">sd_event_ref()</code> increases the reference
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count of the specified event loop object by one.</p><p><code class="function">sd_event_unref()</code> decreases the
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reference count of the specified event loop object by one. If
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the count hits zero, the object is freed. Note that it
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is freed regardless of whether it is the default event loop object for a
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thread or not. This means that allocating an event loop with
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<code class="function">sd_event_default()</code>, then releasing it, and
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then acquiring a new one with
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<code class="function">sd_event_default()</code> will result in two
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distinct objects. Note that in order to free an event loop object,
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all remaining event sources of the event loop also need to be
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freed as each keeps a reference to it.</p></div><div class="refsect1"><a name="idm139650549876304"></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_new()</code> and
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<code class="function">sd_event_default()</code> return 0 or a positive
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integer. On failure, they return a negative errno-style error
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code. <code class="function">sd_event_ref()</code> always returns a pointer
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to the event loop object passed
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in. <code class="function">sd_event_unref()</code> always returns
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<code class="constant">NULL</code>.</p></div><div class="refsect1"><a name="idm139650553826032"></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="-ENOMEM"><span class="term"><code class="constant">-ENOMEM</code></span><a class="headerlink" title="Permalink to this term" href="#-ENOMEM">¶</a></dt><dd><p>Not enough memory to allocate the object.</p></dd><dt id="-EMFILE"><span class="term"><code class="constant">-EMFILE</code></span><a class="headerlink" title="Permalink to this term" href="#-EMFILE">¶</a></dt><dd><p>The maximum number of event loops has been allocated.</p></dd></dl></div></div><div class="refsect1"><a name="idm139650553821536"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p><code class="function">sd_event_new()</code> and the other functions
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described here are available as a shared library, which can be
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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="idm139650553818048"></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="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
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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_add_io.html"><span class="citerefentry"><span class="refentrytitle">sd_event_add_io</span>(3)</span></a>,
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<a href="sd_event_add_time.html"><span class="citerefentry"><span class="refentrytitle">sd_event_add_time</span>(3)</span></a>,
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<a href="sd_event_add_signal.html"><span class="citerefentry"><span class="refentrytitle">sd_event_add_signal</span>(3)</span></a>,
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<a href="sd_event_add_child.html"><span class="citerefentry"><span class="refentrytitle">sd_event_add_child</span>(3)</span></a>,
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<a href="sd_event_add_defer.html"><span class="citerefentry"><span class="refentrytitle">sd_event_add_defer</span>(3)</span></a>,
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<a href="sd_event_add_post.html"><span class="citerefentry"><span class="refentrytitle">sd_event_add_post</span>(3)</span></a>,
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<a href="sd_event_add_exit.html"><span class="citerefentry"><span class="refentrytitle">sd_event_add_exit</span>(3)</span></a>
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</p></div></div></body></html>
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