| <?xml version='1.0'?> <!--*-nxml-*--> |
| <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
| "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
| <!-- SPDX-License-Identifier: LGPL-2.1-or-later --> |
| |
| <refentry id="sd_bus_message_get_monotonic_usec" |
| xmlns:xi="http://www.w3.org/2001/XInclude"> |
| |
| <refentryinfo> |
| <title>sd_bus_message_get_monotonic_usec</title> |
| <productname>systemd</productname> |
| </refentryinfo> |
| |
| <refmeta> |
| <refentrytitle>sd_bus_message_get_monotonic_usec</refentrytitle> |
| <manvolnum>3</manvolnum> |
| </refmeta> |
| |
| <refnamediv> |
| <refname>sd_bus_message_get_monotonic_usec</refname> |
| <refname>sd_bus_message_get_realtime_usec</refname> |
| <refname>sd_bus_message_get_seqnum</refname> |
| <refpurpose>Retrieve the sender timestamps and sequence number of a message</refpurpose> |
| </refnamediv> |
| |
| <refsynopsisdiv> |
| <funcsynopsis> |
| <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> |
| |
| <funcprototype> |
| <funcdef>int <function>sd_bus_message_get_monotonic_usec</function></funcdef> |
| <paramdef>sd_bus_message *<parameter>message</parameter></paramdef> |
| <paramdef>uint64_t *<parameter>usec</parameter></paramdef> |
| </funcprototype> |
| |
| <funcprototype> |
| <funcdef>int <function>sd_bus_message_get_realtime_usec</function></funcdef> |
| <paramdef>sd_bus_message *<parameter>message</parameter></paramdef> |
| <paramdef>uint64_t *<parameter>usec</parameter></paramdef> |
| </funcprototype> |
| |
| <funcprototype> |
| <funcdef>int <function>sd_bus_message_get_seqnum</function></funcdef> |
| <paramdef>sd_bus_message *<parameter>message</parameter></paramdef> |
| <paramdef>uint64_t *<parameter>seqnum</parameter></paramdef> |
| </funcprototype> |
| </funcsynopsis> |
| </refsynopsisdiv> |
| |
| <refsect1> |
| <title>Description</title> |
| |
| <para><function>sd_bus_message_get_monotonic_usec()</function> |
| returns the monotonic timestamp of the time the message was sent. |
| This value is in microseconds since the |
| <constant>CLOCK_MONOTONIC</constant> epoch, see |
| <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry> |
| for details.</para> |
| |
| <para>Similarly, |
| <function>sd_bus_message_get_realtime_usec()</function> 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 <constant>CLOCK_REALTIME</constant> clock.</para> |
| |
| <para><function>sd_bus_message_get_seqnum()</function> 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 buses of the local system. The sequence |
| number combined with the boot ID of the system (as returned by |
| <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>) |
| is a suitable globally unique identifier for bus messages.</para> |
| |
| <para>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.</para> |
| |
| <para>These timestamps and the sequence number are attached to |
| each message by the kernel and cannot be manipulated by the |
| sender.</para> |
| |
| <para>Note that these timestamps are only available on some bus |
| transports, and only after support for them has been negotiated |
| with the |
| <citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| call.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>Return Value</title> |
| |
| <para>On success, these calls return 0 or a positive integer. On |
| failure, these calls return a negative errno-style error |
| code.</para> |
| |
| <para>On success, the timestamp or sequence number is returned in |
| the specified 64-bit unsigned integer variable.</para> |
| |
| <refsect2> |
| <title>Errors</title> |
| |
| <para>Returned errors may indicate the following problems:</para> |
| |
| <variablelist> |
| <varlistentry> |
| <term><constant>-EINVAL</constant></term> |
| |
| <listitem><para>A specified parameter is invalid.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><constant>-ENODATA</constant></term> |
| |
| <listitem><para>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 |
| <citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> |
| </varlistentry> |
| </variablelist> |
| </refsect2> |
| </refsect1> |
| |
| <xi:include href="libsystemd-pkgconfig.xml" /> |
| |
| <refsect1> |
| <title>See Also</title> |
| |
| <para> |
| <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| </para> |
| </refsect1> |
| |
| </refentry> |