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- "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<refentry id="sd_bus_message_get_monotonic_usec" conditional="ENABLE_KDBUS">
- <refentryinfo>
- <title>sd_bus_message_get_monotonic_usec</title>
- <productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
- </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 <literal>CLOCK_MONOTONIC</literal> epoch, see
- <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
- for details.</para>
-
- <para>Similar,
- <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
- <literal>CLOCK_REALTIME</literal> 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 busses 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>
- </refsect1>
-
- <refsect1>
- <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>
- </refsect1>
-
- <refsect1>
- <title>Notes</title>
-
- <para>The
- <function>sd_bus_message_get_monotonic_usec()</function>,
- <function>sd_bus_message_get_realtime_usec()</function>,
- and <function>sd_bus_message_get_seqnum()</function>
- interfaces are available as a shared library, which
- can be compiled and linked to with the
- <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
- file.</para>
- </refsect1>
-
- <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>
+ <refentryinfo>
+ <title>sd_bus_message_get_monotonic_usec</title>
+ <productname>systemd</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Lennart</firstname>
+ <surname>Poettering</surname>
+ <email>lennart@poettering.net</email>
+ </author>
+ </authorgroup>
+ </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>Similar,
+ <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 busses 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>
+ </refsect1>
+
+ <refsect1>
+ <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>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para>The
+ <function>sd_bus_message_get_monotonic_usec()</function>,
+ <function>sd_bus_message_get_realtime_usec()</function>, and
+ <function>sd_bus_message_get_seqnum()</function> interfaces are
+ available as a shared library, which can be compiled and linked to
+ with the
+ <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ file.</para>
+ </refsect1>
+
+ <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>
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