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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>sd_bus_message_get_monotonic_usec</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style>
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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 215</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="idm214167303664"></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>
returns the monotonic timestamp of the time the
message was sent. This value is in microseconds since
the "<code class="literal">CLOCK_MONOTONIC</code>" epoch, see
<a href="clock_gettime.html"><span class="citerefentry"><span class="refentrytitle">clock_gettime</span>(2)</span></a>
for details.</p><p>Similar,
<code class="function">sd_bus_message_get_realtime_usec()</code>
returns the realtime (wallclock) timestamp of the time
the message was sent. This value is in microseconds
since Jan 1st, 1970, i.e. in the
"<code class="literal">CLOCK_REALTIME</code>" clock.</p><p><code class="function">sd_bus_message_get_seqnum()</code>
returns the kernel-assigned sequence number of the
message. The kernel assigns a global, monotonically
increasing sequence number to all messages transmitted
on the local system, at the time the message was
sent. This sequence number is useful for determining
message send order, even across different busses of
the local system. The sequence number combined with
the boot ID of the system (as returned by
<a href="sd_id128_get_boot.html"><span class="citerefentry"><span class="refentrytitle">sd_id128_get_boot</span>(3)</span></a>)
is a suitable globally unique identifier for bus
messages.</p><p>Note that the sending order and receiving order
of messages might differ, in particular for broadcast
messages. This means that the sequence number and the
timestamps of messages a client reads are not
necessarily monotonically increasing.</p><p>These timestamps and the sequence number are
attached to each message by the kernel and cannot be
manipulated by the sender.</p><p>Note that these timestamps are only available on
some bus transports, and only after support for them
has been negotiated with the
<a href="sd_bus_negotiate_timestamp.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_negotiate_timestamp</span>(3)</span></a>
call.</p></div><div class="refsect1"><a name="idm214166630240"></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 failure, these calls return a negative
errno-style error code.</p><p>On success, the timestamp or sequence number is
returned in the specified 64-bit unsigned integer
variable.</p></div><div class="refsect1"><a name="idm214166835648"></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="varname">-EINVAL</code></span><a class="headerlink" title="Permalink to this term" href="#-EINVAL">¶</a></dt><dd><p>A specified parameter
is invalid.</p></dd><dt id="-ENODATA"><span class="term"><code class="varname">-ENODATA</code></span><a class="headerlink" title="Permalink to this term" href="#-ENODATA">¶</a></dt><dd><p>No timestamp or
sequence number information is
attached to the passed message. This
error is returned if the underlying
transport does not support
timestamping or assigning of sequence
numbers, or if this feature has not
been negotiated with
<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="idm214166448368"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p>The
<code class="function">sd_bus_message_get_monotonic_usec()</code>,
<code class="function">sd_bus_message_get_realtime_usec()</code>,
and <code class="function">sd_bus_message_get_seqnum()</code>
interfaces are available as a shared library, which
can be compiled and linked to with the
<code class="constant">libsystemd</code> <a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
file.</p></div><div class="refsect1"><a name="idm214168606432"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
<a href="sd-bus.html"><span class="citerefentry"><span class="refentrytitle">sd-bus</span>(3)</span></a>,
<a href="sd_bus_new.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_new</span>(3)</span></a>,
<a href="sd_bus_negotiate_timestamp.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_negotiate_timestamp</span>(3)</span></a>,
<a href="clock_gettime.html"><span class="citerefentry"><span class="refentrytitle">clock_gettime</span>(2)</span></a>,
<a href="sd_id128_get_boot.html"><span class="citerefentry"><span class="refentrytitle">sd_id128_get_boot</span>(3)</span></a>
</p></div></div></body></html>
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