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5eef597e | 22 | <a href="../libudev/index.html">gudev </a><span style="float:right">systemd 217</span><hr><div class="refentry"><a name="sd_event_add_time"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_event_add_time, sd_event_source_get_time, sd_event_source_set_time, sd_event_source_get_time_accuracy, sd_event_source_set_time_accuracy, sd_event_source_get_time_clock — Add a timer event source 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_time</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>clockid_t <var class="pdparam">clock</var>, </td></tr><tr><td> </td><td>uint64_t <var class="pdparam">usec</var>, </td></tr><tr><td> </td><td>uint64_t <var class="pdparam">accuracy</var>, </td></tr><tr><td> </td><td>sd_event_time_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_time_handler_t</b>)(</code></td><td>sd_event_source *<var class="pdparam">s</var>, </td></tr><tr><td> </td><td>uint64_t <var class="pdparam">usec</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_source_get_time</b>(</code></td><td>sd_event_source *<var class="pdparam">source</var>, </td></tr><tr><td> </td><td>usec_t *<var class="pdparam">usec</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_source_set_time</b>(</code></td><td>sd_event_source *<var class="pdparam">source</var>, </td></tr><tr><td> </td><td>usec_t <var class="pdparam">usec</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_source_get_time_accuracy</b>(</code></td><td>sd_event_source *<var class="pdparam">source</var>, </td></tr><tr><td> </td><td>usec_t *<var class="pdparam">usec</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_source_set_time_accuracy</b>(</code></td><td>sd_event_source *<var class="pdparam">source</var>, </td></tr><tr><td> </td><td>usec_t <var class="pdparam">usec</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_source_get_time_clock</b>(</code></td><td>sd_event_source *<var class="pdparam">source</var>, </td></tr><tr><td> </td><td>clockid_t *<var class="pdparam">clock</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm214188667792"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_event_add_time()</code> adds a new timer |
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23 | event source to an event loop object. The event loop is specified |
24 | in <em class="parameter"><code>event</code></em>, the event source is returned in | |
25 | the <em class="parameter"><code>source</code></em> parameter. The | |
26 | <em class="parameter"><code>clock</code></em> parameter takes a clock identifier, | |
27 | one of <code class="constant">CLOCK_REALTIME</code>, | |
28 | <code class="constant">CLOCK_MONOTONIC</code> and | |
29 | <code class="constant">CLOCK_BOOTTIME_ALARM</code>. See | |
5eef597e | 30 | <a href="http://man7.org/linux/man-pages/man2/timerfd_create.2.html"><span class="citerefentry"><span class="refentrytitle">timerfd_create</span>(2)</span></a> |
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31 | for details regarding the various types of clocks. The |
32 | <em class="parameter"><code>usec</code></em> parameter takes a time value in | |
33 | microseconds, relative to the clock's epoch specifying when the | |
34 | timer shall elapse the earliest. The | |
35 | <em class="parameter"><code>accuracy</code></em> parameter takes an additional | |
36 | accuracy value in microseconds specifying a time the timer event | |
37 | may be delayed. Specify 0 for selecting the default accuracy | |
38 | (250ms). Specify 1 for most accurate timers. Consider specifying | |
39 | 60000000 or larger (1h) for long-running events that may be | |
40 | delayed substantially. Picking higher accuracy values allows the | |
41 | system to coalesce timer events more aggressively, thus improving | |
42 | power efficiency. The <em class="parameter"><code>handler</code></em> shall | |
43 | reference a function to call when the timer elapses. The handler | |
44 | function will be passed the <em class="parameter"><code>userdata</code></em> | |
45 | pointer, which may be chosen freely by the caller. The handler is | |
46 | also passed the configured time it was triggered, however it might | |
47 | actually have been called at a slightly later time, subject to the | |
48 | specified accuracy value, the kernel timer slack (see | |
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49 | <a href="http://man7.org/linux/man-pages/man2/prctl.2.html"><span class="citerefentry"><span class="refentrytitle">prctl</span>(2)</span></a>) |
50 | and additional scheduling latencies.</p><p>By default, the timer will elapse once | |
51 | (<code class="constant">SD_EVENT_ONESHOT</code>), but this may be changed | |
52 | with | |
53 | <a href="sd_event_source_set_enabled.html"><span class="citerefentry"><span class="refentrytitle">sd_event_source_set_enabled</span>(3)</span></a>. | |
54 | If the handler function returns a negative error code, it will be | |
55 | disabled after the invocation, even if | |
56 | <code class="constant">SD_EVENT_ON</code> mode is set. | |
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57 | </p><p><code class="function">sd_event_source_get_time()</code> retrieves |
58 | the configured time value of a timer event source created | |
59 | previously with <code class="function">sd_event_add_time()</code>. It takes | |
60 | the event source object and a pointer to a variable to store the | |
61 | time in microseconds in.</p><p><code class="function">sd_event_source_set_time()</code> changes the | |
62 | configured time value of a timer event source created previously | |
63 | with <code class="function">sd_event_add_time()</code>. It takes the event | |
64 | source object and a time relative to the selected clock's | |
65 | epoch, in microseconds.</p><p><code class="function">sd_event_source_get_time_accuracy()</code> | |
66 | retrieves the configured accuracy value of a timer event source | |
67 | created previously with <code class="function">sd_event_add_time()</code>. It | |
68 | takes the event source object and a pointer to a variable to store | |
69 | the accuracy in microseconds in.</p><p><code class="function">sd_event_source_set_time_accuracy()</code> | |
70 | changes the configured accuracy of a timer event source created | |
71 | previously with <code class="function">sd_event_add_time()</code>. It takes | |
72 | the event source object and an accuracy, in microseconds.</p><p><code class="function">sd_event_source_get_time_clock()</code> | |
73 | retrieves the configured clock of a timer event source created | |
74 | previously with <code class="function">sd_event_add_time()</code>. It takes | |
75 | the event source object and a pointer to a variable to store the | |
5eef597e | 76 | clock identifier in.</p></div><div class="refsect1"><a name="idm214188638272"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>On success, these functions return 0 or a positive |
60f067b4 | 77 | integer. On failure, they return a negative errno-style error |
5eef597e | 78 | code. </p></div><div class="refsect1"><a name="idm214188636944"></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><dt id="-ENOTSUP"><span class="term"><code class="constant">-ENOTSUP</code></span><a class="headerlink" title="Permalink to this term" href="#-ENOTSUP">¶</a></dt><dd><p>The selected clock is not supported by the event loop implementation.</p></dd></dl></div></div><div class="refsect1"><a name="idm214188628032"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p><code class="function">sd_event_add_time()</code> and the other functions |
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79 | described here are available as a shared library, which can be |
80 | compiled and linked to with the | |
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81 | <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> |
82 | file.</p></div><div class="refsect1"><a name="idm214183947136"></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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83 | <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>, |
84 | <a href="sd-event.html"><span class="citerefentry"><span class="refentrytitle">sd-event</span>(3)</span></a>, | |
85 | <a href="sd_event_new.html"><span class="citerefentry"><span class="refentrytitle">sd_event_new</span>(3)</span></a>, | |
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86 | <a href="sd_event_add_signal.html"><span class="citerefentry"><span class="refentrytitle">sd_event_add_signal</span>(3)</span></a>, |
87 | <a href="sd_event_add_child.html"><span class="citerefentry"><span class="refentrytitle">sd_event_add_child</span>(3)</span></a>, | |
88 | <a href="sd_event_add_defer.html"><span class="citerefentry"><span class="refentrytitle">sd_event_add_defer</span>(3)</span></a>, | |
89 | <a href="http://man7.org/linux/man-pages/man2/clock_gettime.2.html"><span class="citerefentry"><span class="refentrytitle">clock_gettime</span>(2)</span></a>, | |
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90 | <a href="sd_event_source_set_enabled.html"><span class="citerefentry"><span class="refentrytitle">sd_event_source_set_enabled</span>(3)</span></a> |
91 | </p></div></div></body></html> |