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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_bus_message_get_monotonic_usec"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_bus_message_get_monotonic_usec, sd_bus_message_get_realtime_usec, sd_bus_message_get_seqnum — Retrieve the sender timestamps and sequence number of a message</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_bus_message_get_monotonic_usec</b>(</code></td><td>sd_bus_message *<var class="pdparam">message</var>, </td></tr><tr><td> </td><td>uint64_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_bus_message_get_realtime_usec</b>(</code></td><td>sd_bus_message *<var class="pdparam">message</var>, </td></tr><tr><td> </td><td>uint64_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_bus_message_get_seqnum</b>(</code></td><td>sd_bus_message *<var class="pdparam">message</var>, </td></tr><tr><td> </td><td>uint64_t *<var class="pdparam">seqnum</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm140134631967504"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_bus_message_get_monotonic_usec()</code>
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returns the monotonic timestamp of the time the message was sent.
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This value is in microseconds since the
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<code class="constant">CLOCK_MONOTONIC</code> epoch, see
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<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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for details.</p><p>Similar,
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<code class="function">sd_bus_message_get_realtime_usec()</code> returns
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the realtime (wallclock) timestamp of the time the message was
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sent. This value is in microseconds since Jan 1st, 1970, i.e. in
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the <code class="constant">CLOCK_REALTIME</code> clock.</p><p><code class="function">sd_bus_message_get_seqnum()</code> returns the
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kernel-assigned sequence number of the message. The kernel assigns
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a global, monotonically increasing sequence number to all messages
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transmitted on the local system, at the time the message was sent.
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This sequence number is useful for determining message send order,
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even across different busses of the local system. The sequence
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number combined with the boot ID of the system (as returned by
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<a href="sd_id128_get_boot.html"><span class="citerefentry"><span class="refentrytitle">sd_id128_get_boot</span>(3)</span></a>)
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is a suitable globally unique identifier for bus messages.</p><p>Note that the sending order and receiving order of messages
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might differ, in particular for broadcast messages. This means
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that the sequence number and the timestamps of messages a client
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reads are not necessarily monotonically increasing.</p><p>These timestamps and the sequence number are attached to
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each message by the kernel and cannot be manipulated by the
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sender.</p><p>Note that these timestamps are only available on some bus
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transports, and only after support for them has been negotiated
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with the
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<a href="sd_bus_negotiate_timestamp.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_negotiate_timestamp</span>(3)</span></a>
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call.</p></div><div class="refsect1"><a name="idm140134635860864"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>On success, these calls return 0 or a positive integer. On
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failure, these calls return a negative errno-style error
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code.</p><p>On success, the timestamp or sequence number is returned in
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the specified 64-bit unsigned integer variable.</p></div><div class="refsect1"><a name="idm140134635859024"></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>A specified parameter is
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invalid.</p></dd><dt id="-ENODATA"><span class="term"><code class="constant">-ENODATA</code></span><a class="headerlink" title="Permalink to this term" href="#-ENODATA">¶</a></dt><dd><p>No timestamp or sequence number information is
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attached to the passed message. This error is returned if the
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underlying transport does not support timestamping or
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assigning of sequence numbers, or if this feature has not been
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negotiated with
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<a href="sd_bus_negotiate_timestamp.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_negotiate_timestamp</span>(3)</span></a>.</p></dd></dl></div></div><div class="refsect1"><a name="idm140134635853408"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p>The
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<code class="function">sd_bus_message_get_monotonic_usec()</code>,
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<code class="function">sd_bus_message_get_realtime_usec()</code>, and
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<code class="function">sd_bus_message_get_seqnum()</code> interfaces are
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available as a shared library, which can be compiled and linked to
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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="idm140134635840944"></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-bus.html"><span class="citerefentry"><span class="refentrytitle">sd-bus</span>(3)</span></a>,
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<a href="sd_bus_new.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_new</span>(3)</span></a>,
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<a href="sd_bus_negotiate_timestamp.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_negotiate_timestamp</span>(3)</span></a>,
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<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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<a href="sd_id128_get_boot.html"><span class="citerefentry"><span class="refentrytitle">sd_id128_get_boot</span>(3)</span></a>
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</p></div></div></body></html>
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