| <?xml version='1.0'?> <!--*-nxml-*--> |
| <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
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| Copyright 2013 Lennart Poettering |
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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><varname>-EINVAL</varname></term> |
| |
| <listitem><para>A specified parameter |
| is invalid.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>-ENODATA</varname></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><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> |