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<refentry id= "sd_bus_message_get_monotonic_usec" conditional= "ENABLE_KDBUS" >
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<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>
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<paramdef > sd_bus_message *<parameter > message</parameter> </paramdef>
<paramdef > uint64_t *<parameter > usec</parameter> </paramdef>
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</funcprototype>
<funcprototype >
<funcdef > int <function > sd_bus_message_get_realtime_usec</function> </funcdef>
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<paramdef > sd_bus_message *<parameter > message</parameter> </paramdef>
<paramdef > uint64_t *<parameter > usec</parameter> </paramdef>
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</funcprototype>
<funcprototype >
<funcdef > int <function > sd_bus_message_get_seqnum</function> </funcdef>
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<paramdef > sd_bus_message *<parameter > message</parameter> </paramdef>
<paramdef > uint64_t *<parameter > seqnum</parameter> </paramdef>
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</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
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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
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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>
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<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>
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<para > These timestamps and the sequence number are
attached to each message by the kernel and cannot be
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manipulated by the sender.</para>
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<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
man: add a mapping for external manpages
It is annoying when we have dead links on fd.o.
Add project='man-pages|die-net|archlinux' to <citerefentry>-ies.
In generated html, add external links to
http://man7.org/linux/man-pages/man, http://linux.die.net/man/,
https://www.archlinux.org/.
By default, pages in sections 2 and 4 go to man7, since Michael
Kerrisk is the autorative source on kernel related stuff.
The rest of links goes to linux.die.net, because they have the
manpages.
Except for the pacman stuff, since it seems to be only available from
archlinux.org.
Poor gummiboot gets no link, because gummitboot(8) ain't to be found
on the net. According to common wisdom, that would mean that it does
not exist. But I have seen Kay using it, so I know it does, and
deserves to be found. Can somebody be nice and put it up somewhere?
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<constant > libsystemd</constant> <citerefentry project= 'die-net' > <refentrytitle > pkg-config</refentrytitle> <manvolnum > 1</manvolnum> </citerefentry>
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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>
