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1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
e735f4d4 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
6 | This file is part of systemd. | |
7 | ||
8 | Copyright 2013 Lennart Poettering | |
9 | ||
10 | systemd is free software; you can redistribute it and/or modify it | |
11 | under the terms of the GNU Lesser General Public License as published by | |
12 | the Free Software Foundation; either version 2.1 of the License, or | |
13 | (at your option) any later version. | |
14 | ||
15 | systemd is distributed in the hope that it will be useful, but | |
16 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
18 | Lesser General Public License for more details. | |
19 | ||
20 | You should have received a copy of the GNU Lesser General Public License | |
21 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
22 | --> | |
23 | ||
24 | <refentry id="sd_bus_message_get_monotonic_usec" conditional="ENABLE_KDBUS"> | |
25 | ||
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26 | <refentryinfo> |
27 | <title>sd_bus_message_get_monotonic_usec</title> | |
28 | <productname>systemd</productname> | |
29 | ||
30 | <authorgroup> | |
31 | <author> | |
32 | <contrib>Developer</contrib> | |
33 | <firstname>Lennart</firstname> | |
34 | <surname>Poettering</surname> | |
35 | <email>lennart@poettering.net</email> | |
36 | </author> | |
37 | </authorgroup> | |
38 | </refentryinfo> | |
39 | ||
40 | <refmeta> | |
41 | <refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle> | |
42 | <manvolnum>3</manvolnum> | |
43 | </refmeta> | |
44 | ||
45 | <refnamediv> | |
46 | <refname>sd_bus_message_get_monotonic_usec</refname> | |
47 | <refname>sd_bus_message_get_realtime_usec</refname> | |
48 | <refname>sd_bus_message_get_seqnum</refname> | |
49 | <refpurpose>Retrieve the sender timestamps and sequence number of a message</refpurpose> | |
50 | </refnamediv> | |
51 | ||
52 | <refsynopsisdiv> | |
53 | <funcsynopsis> | |
54 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
55 | ||
56 | <funcprototype> | |
57 | <funcdef>int <function>sd_bus_message_get_monotonic_usec</function></funcdef> | |
58 | <paramdef>sd_bus_message *<parameter>message</parameter></paramdef> | |
59 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> | |
60 | </funcprototype> | |
61 | ||
62 | <funcprototype> | |
63 | <funcdef>int <function>sd_bus_message_get_realtime_usec</function></funcdef> | |
64 | <paramdef>sd_bus_message *<parameter>message</parameter></paramdef> | |
65 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> | |
66 | </funcprototype> | |
67 | ||
68 | <funcprototype> | |
69 | <funcdef>int <function>sd_bus_message_get_seqnum</function></funcdef> | |
70 | <paramdef>sd_bus_message *<parameter>message</parameter></paramdef> | |
71 | <paramdef>uint64_t *<parameter>seqnum</parameter></paramdef> | |
72 | </funcprototype> | |
73 | </funcsynopsis> | |
74 | </refsynopsisdiv> | |
75 | ||
76 | <refsect1> | |
77 | <title>Description</title> | |
78 | ||
79 | <para><function>sd_bus_message_get_monotonic_usec()</function> | |
80 | returns the monotonic timestamp of the time the message was sent. | |
81 | This value is in microseconds since the | |
82 | <constant>CLOCK_MONOTONIC</constant> epoch, see | |
83 | <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
84 | for details.</para> | |
85 | ||
86 | <para>Similar, | |
87 | <function>sd_bus_message_get_realtime_usec()</function> returns | |
88 | the realtime (wallclock) timestamp of the time the message was | |
89 | sent. This value is in microseconds since Jan 1st, 1970, i.e. in | |
90 | the <constant>CLOCK_REALTIME</constant> clock.</para> | |
91 | ||
92 | <para><function>sd_bus_message_get_seqnum()</function> returns the | |
93 | kernel-assigned sequence number of the message. The kernel assigns | |
94 | a global, monotonically increasing sequence number to all messages | |
95 | transmitted on the local system, at the time the message was sent. | |
96 | This sequence number is useful for determining message send order, | |
97 | even across different busses of the local system. The sequence | |
98 | number combined with the boot ID of the system (as returned by | |
99 | <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>) | |
100 | is a suitable globally unique identifier for bus messages.</para> | |
101 | ||
102 | <para>Note that the sending order and receiving order of messages | |
103 | might differ, in particular for broadcast messages. This means | |
104 | that the sequence number and the timestamps of messages a client | |
105 | reads are not necessarily monotonically increasing.</para> | |
106 | ||
107 | <para>These timestamps and the sequence number are attached to | |
108 | each message by the kernel and cannot be manipulated by the | |
109 | sender.</para> | |
110 | ||
111 | <para>Note that these timestamps are only available on some bus | |
112 | transports, and only after support for them has been negotiated | |
113 | with the | |
114 | <citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
115 | call.</para> | |
116 | </refsect1> | |
117 | ||
118 | <refsect1> | |
119 | <title>Return Value</title> | |
120 | ||
121 | <para>On success, these calls return 0 or a positive integer. On | |
122 | failure, these calls return a negative errno-style error | |
123 | code.</para> | |
124 | ||
125 | <para>On success, the timestamp or sequence number is returned in | |
126 | the specified 64-bit unsigned integer variable.</para> | |
127 | </refsect1> | |
128 | ||
129 | <refsect1> | |
130 | <title>Errors</title> | |
131 | ||
132 | <para>Returned errors may indicate the following problems:</para> | |
133 | ||
134 | <variablelist> | |
135 | <varlistentry> | |
136 | <term><constant>-EINVAL</constant></term> | |
137 | ||
138 | <listitem><para>A specified parameter is | |
139 | invalid.</para></listitem> | |
140 | </varlistentry> | |
141 | ||
142 | <varlistentry> | |
143 | <term><constant>-ENODATA</constant></term> | |
144 | ||
145 | <listitem><para>No timestamp or sequence number information is | |
146 | attached to the passed message. This error is returned if the | |
147 | underlying transport does not support timestamping or | |
148 | assigning of sequence numbers, or if this feature has not been | |
149 | negotiated with | |
150 | <citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> | |
151 | </varlistentry> | |
152 | </variablelist> | |
153 | </refsect1> | |
154 | ||
155 | <refsect1> | |
156 | <title>Notes</title> | |
157 | ||
158 | <para>The | |
159 | <function>sd_bus_message_get_monotonic_usec()</function>, | |
160 | <function>sd_bus_message_get_realtime_usec()</function>, and | |
161 | <function>sd_bus_message_get_seqnum()</function> interfaces are | |
162 | available as a shared library, which can be compiled and linked to | |
163 | with the | |
164 | <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
165 | file.</para> | |
166 | </refsect1> | |
167 | ||
168 | <refsect1> | |
169 | <title>See Also</title> | |
170 | ||
171 | <para> | |
172 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
173 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
174 | <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
175 | <citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
176 | <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
177 | <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
178 | </para> | |
179 | </refsect1> | |
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180 | |
181 | </refentry> |