]>
Commit | Line | Data |
---|---|---|
37369553 LP |
1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
37369553 LP |
4 | |
5 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
37369553 LP |
7 | --> |
8 | ||
7d6b2723 ZJS |
9 | <refentry id="sd_bus_message_get_monotonic_usec" |
10 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
37369553 | 11 | |
798d3a52 ZJS |
12 | <refentryinfo> |
13 | <title>sd_bus_message_get_monotonic_usec</title> | |
14 | <productname>systemd</productname> | |
798d3a52 ZJS |
15 | </refentryinfo> |
16 | ||
17 | <refmeta> | |
18 | <refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle> | |
19 | <manvolnum>3</manvolnum> | |
20 | </refmeta> | |
21 | ||
22 | <refnamediv> | |
23 | <refname>sd_bus_message_get_monotonic_usec</refname> | |
24 | <refname>sd_bus_message_get_realtime_usec</refname> | |
25 | <refname>sd_bus_message_get_seqnum</refname> | |
26 | <refpurpose>Retrieve the sender timestamps and sequence number of a message</refpurpose> | |
27 | </refnamediv> | |
28 | ||
29 | <refsynopsisdiv> | |
30 | <funcsynopsis> | |
31 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
32 | ||
33 | <funcprototype> | |
34 | <funcdef>int <function>sd_bus_message_get_monotonic_usec</function></funcdef> | |
35 | <paramdef>sd_bus_message *<parameter>message</parameter></paramdef> | |
36 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> | |
37 | </funcprototype> | |
38 | ||
39 | <funcprototype> | |
40 | <funcdef>int <function>sd_bus_message_get_realtime_usec</function></funcdef> | |
41 | <paramdef>sd_bus_message *<parameter>message</parameter></paramdef> | |
42 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> | |
43 | </funcprototype> | |
44 | ||
45 | <funcprototype> | |
46 | <funcdef>int <function>sd_bus_message_get_seqnum</function></funcdef> | |
47 | <paramdef>sd_bus_message *<parameter>message</parameter></paramdef> | |
48 | <paramdef>uint64_t *<parameter>seqnum</parameter></paramdef> | |
49 | </funcprototype> | |
50 | </funcsynopsis> | |
51 | </refsynopsisdiv> | |
52 | ||
53 | <refsect1> | |
54 | <title>Description</title> | |
55 | ||
56 | <para><function>sd_bus_message_get_monotonic_usec()</function> | |
57 | returns the monotonic timestamp of the time the message was sent. | |
58 | This value is in microseconds since the | |
59 | <constant>CLOCK_MONOTONIC</constant> epoch, see | |
60 | <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
61 | for details.</para> | |
62 | ||
a8eaaee7 | 63 | <para>Similarly, |
798d3a52 ZJS |
64 | <function>sd_bus_message_get_realtime_usec()</function> returns |
65 | the realtime (wallclock) timestamp of the time the message was | |
66 | sent. This value is in microseconds since Jan 1st, 1970, i.e. in | |
67 | the <constant>CLOCK_REALTIME</constant> clock.</para> | |
68 | ||
69 | <para><function>sd_bus_message_get_seqnum()</function> returns the | |
70 | kernel-assigned sequence number of the message. The kernel assigns | |
71 | a global, monotonically increasing sequence number to all messages | |
72 | transmitted on the local system, at the time the message was sent. | |
73 | This sequence number is useful for determining message send order, | |
ff9b60f3 | 74 | even across different buses of the local system. The sequence |
798d3a52 ZJS |
75 | number combined with the boot ID of the system (as returned by |
76 | <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>) | |
77 | is a suitable globally unique identifier for bus messages.</para> | |
78 | ||
79 | <para>Note that the sending order and receiving order of messages | |
80 | might differ, in particular for broadcast messages. This means | |
81 | that the sequence number and the timestamps of messages a client | |
82 | reads are not necessarily monotonically increasing.</para> | |
83 | ||
84 | <para>These timestamps and the sequence number are attached to | |
85 | each message by the kernel and cannot be manipulated by the | |
86 | sender.</para> | |
87 | ||
88 | <para>Note that these timestamps are only available on some bus | |
89 | transports, and only after support for them has been negotiated | |
90 | with the | |
91 | <citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
92 | call.</para> | |
93 | </refsect1> | |
94 | ||
95 | <refsect1> | |
96 | <title>Return Value</title> | |
97 | ||
98 | <para>On success, these calls return 0 or a positive integer. On | |
99 | failure, these calls return a negative errno-style error | |
100 | code.</para> | |
101 | ||
102 | <para>On success, the timestamp or sequence number is returned in | |
103 | the specified 64-bit unsigned integer variable.</para> | |
104 | </refsect1> | |
105 | ||
106 | <refsect1> | |
107 | <title>Errors</title> | |
108 | ||
109 | <para>Returned errors may indicate the following problems:</para> | |
110 | ||
111 | <variablelist> | |
112 | <varlistentry> | |
113 | <term><constant>-EINVAL</constant></term> | |
114 | ||
115 | <listitem><para>A specified parameter is | |
116 | invalid.</para></listitem> | |
117 | </varlistentry> | |
118 | ||
119 | <varlistentry> | |
120 | <term><constant>-ENODATA</constant></term> | |
121 | ||
122 | <listitem><para>No timestamp or sequence number information is | |
123 | attached to the passed message. This error is returned if the | |
124 | underlying transport does not support timestamping or | |
125 | assigning of sequence numbers, or if this feature has not been | |
126 | negotiated with | |
127 | <citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> | |
128 | </varlistentry> | |
129 | </variablelist> | |
130 | </refsect1> | |
131 | ||
7d6b2723 | 132 | <xi:include href="libsystemd-pkgconfig.xml" /> |
798d3a52 ZJS |
133 | |
134 | <refsect1> | |
135 | <title>See Also</title> | |
136 | ||
137 | <para> | |
138 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
139 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
140 | <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
141 | <citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
142 | <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
143 | <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
144 | </para> | |
145 | </refsect1> | |
37369553 LP |
146 | |
147 | </refentry> |