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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_add_defer"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_event_add_defer, sd_event_add_post, sd_event_add_exit — Add static event sources to an event loop</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_add_defer</b>(</code></td><td>sd_event *<var class="pdparam">event</var>, </td></tr><tr><td> </td><td>sd_event_source **<var class="pdparam">source</var>, </td></tr><tr><td> </td><td>sd_event_handler_t <var class="pdparam">handler</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">userdata</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_add_post</b>(</code></td><td>sd_event *<var class="pdparam">event</var>, </td></tr><tr><td> </td><td>sd_event_source **<var class="pdparam">source</var>, </td></tr><tr><td> </td><td>sd_event_handler_t <var class="pdparam">handler</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">userdata</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_add_exit</b>(</code></td><td>sd_event *<var class="pdparam">event</var>, </td></tr><tr><td> </td><td>sd_event_source **<var class="pdparam">source</var>, </td></tr><tr><td> </td><td>sd_event_handler_t <var class="pdparam">handler</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">userdata</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">typedef int (*<b class="fsfunc">sd_event_handler_t</b>)(</code></td><td>sd_event_source *<var class="pdparam">s</var>, </td></tr><tr><td> </td><td>void *<var class="pdparam">userdata</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm140723014876032"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p>Those three functions add new event sources to an event loop
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object. The event loop is specified in
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<em class="parameter"><code>event</code></em>, the event source is returned in the
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<em class="parameter"><code>source</code></em> parameter. The event sources are
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enabled statically and will "fire" when the event loop is run and
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the conditions described below are met. The handler function will
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be passed the <em class="parameter"><code>userdata</code></em> pointer, which may
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be chosen freely by the caller.</p><p><code class="function">sd_event_add_defer()</code> adds a new event
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source that will "fire" the next time the event loop is run. By
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default, the handler will be called once
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(<code class="constant">SD_EVENT_ONESHOT</code>).</p><p><code class="function">sd_event_add_post()</code> adds a new event
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source that will "fire" if any event handlers are invoked whenever
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the event loop is run. By default, the source is enabled
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permanently (<code class="constant">SD_EVENT_ON</code>).</p><p><code class="function">sd_event_add_exit()</code> adds a new event
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source that will "fire" when the event loop is terminated
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with <code class="function">sd_event_exit()</code>.</p><p>The
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<a href="sd_event_source_set_enabled.html"><span class="citerefentry"><span class="refentrytitle">sd_event_source_set_enabled</span>(3)</span></a>
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function may be used to enable the event source permanently
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(<code class="constant">SD_EVENT_ON</code>) or to make it fire just once
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(<code class="constant">SD_EVENT_ONESHOT</code>). If the handler function
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returns a negative error code, it will be disabled after the
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invocation, even if <code class="constant">SD_EVENT_ON</code> mode is
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set.</p></div><div class="refsect1"><a name="idm140723018767568"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>On success, this functions return 0 or a positive
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integer. On failure, they return a negative errno-style error
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code.</p></div><div class="refsect1"><a name="idm140723018766240"></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 an object.</p></dd><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>An invalid argument has been passed.</p></dd><dt id="-ESTALE"><span class="term"><code class="constant">-ESTALE</code></span><a class="headerlink" title="Permalink to this term" href="#-ESTALE">¶</a></dt><dd><p>The event loop is already terminated.</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="idm140723018758816"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p>Functions described here are available as a shared library,
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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="idm140723018748608"></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_new.html"><span class="citerefentry"><span class="refentrytitle">sd_event_new</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_source_set_enabled.html"><span class="citerefentry"><span class="refentrytitle">sd_event_source_set_enabled</span>(3)</span></a>
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</p></div></div></body></html>
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