1 <?xml version='1.0'?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
6 This file is part of elogind.
7 SPDX-License-Identifier: LGPL-2.1+
10 Copyright 2013 Lennart Poettering
13 <refentry id="sd_bus_message_get_monotonic_usec"
14 xmlns:xi="http://www.w3.org/2001/XInclude">
17 <title>sd_bus_message_get_monotonic_usec</title>
18 <productname>elogind</productname>
22 <contrib>Developer</contrib>
23 <firstname>Lennart</firstname>
24 <surname>Poettering</surname>
25 <email>lennart@poettering.net</email>
31 <refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle>
32 <manvolnum>3</manvolnum>
36 <refname>sd_bus_message_get_monotonic_usec</refname>
37 <refname>sd_bus_message_get_realtime_usec</refname>
38 <refname>sd_bus_message_get_seqnum</refname>
39 <refpurpose>Retrieve the sender timestamps and sequence number of a message</refpurpose>
44 <funcsynopsisinfo>#include <elogind/sd-bus.h></funcsynopsisinfo>
47 <funcdef>int <function>sd_bus_message_get_monotonic_usec</function></funcdef>
48 <paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
49 <paramdef>uint64_t *<parameter>usec</parameter></paramdef>
53 <funcdef>int <function>sd_bus_message_get_realtime_usec</function></funcdef>
54 <paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
55 <paramdef>uint64_t *<parameter>usec</parameter></paramdef>
59 <funcdef>int <function>sd_bus_message_get_seqnum</function></funcdef>
60 <paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
61 <paramdef>uint64_t *<parameter>seqnum</parameter></paramdef>
67 <title>Description</title>
69 <para><function>sd_bus_message_get_monotonic_usec()</function>
70 returns the monotonic timestamp of the time the message was sent.
71 This value is in microseconds since the
72 <constant>CLOCK_MONOTONIC</constant> epoch, see
73 <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
77 <function>sd_bus_message_get_realtime_usec()</function> returns
78 the realtime (wallclock) timestamp of the time the message was
79 sent. This value is in microseconds since Jan 1st, 1970, i.e. in
80 the <constant>CLOCK_REALTIME</constant> clock.</para>
82 <para><function>sd_bus_message_get_seqnum()</function> returns the
83 kernel-assigned sequence number of the message. The kernel assigns
84 a global, monotonically increasing sequence number to all messages
85 transmitted on the local system, at the time the message was sent.
86 This sequence number is useful for determining message send order,
87 even across different buses of the local system. The sequence
88 number combined with the boot ID of the system (as returned by
89 <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>)
90 is a suitable globally unique identifier for bus messages.</para>
92 <para>Note that the sending order and receiving order of messages
93 might differ, in particular for broadcast messages. This means
94 that the sequence number and the timestamps of messages a client
95 reads are not necessarily monotonically increasing.</para>
97 <para>These timestamps and the sequence number are attached to
98 each message by the kernel and cannot be manipulated by the
101 <para>Note that these timestamps are only available on some bus
102 transports, and only after support for them has been negotiated
104 <citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry>
109 <title>Return Value</title>
111 <para>On success, these calls return 0 or a positive integer. On
112 failure, these calls return a negative errno-style error
115 <para>On success, the timestamp or sequence number is returned in
116 the specified 64-bit unsigned integer variable.</para>
120 <title>Errors</title>
122 <para>Returned errors may indicate the following problems:</para>
126 <term><constant>-EINVAL</constant></term>
128 <listitem><para>A specified parameter is
129 invalid.</para></listitem>
133 <term><constant>-ENODATA</constant></term>
135 <listitem><para>No timestamp or sequence number information is
136 attached to the passed message. This error is returned if the
137 underlying transport does not support timestamping or
138 assigning of sequence numbers, or if this feature has not been
140 <citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
145 <xi:include href="libelogind-pkgconfig.xml" />
148 <title>See Also</title>
151 <!-- 0 /// elogind is in section 8
152 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
154 <citerefentry><refentrytitle>elogind</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
156 <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
157 <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
158 <citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
159 <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
160 <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>