x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_BUS_MESSAGE_GET_MONOsd_bus_message_get_SD_BUS_MESSAGE_GET_MONOTONIC_USEC(3)
NAME
sd_bus_message_get_monotonic_usec, sd_bus_message_get_realtime_usec,
sd_bus_message_get_seqnum - Retrieve the sender timestamps and sequence
number of a message
SYNOPSIS
#include <systemd/sd-bus.h>
int sd_bus_message_get_monotonic_usec(sd_bus_message *message,
uint64_t *usec);
int sd_bus_message_get_realtime_usec(sd_bus_message *message,
uint64_t *usec);
int sd_bus_message_get_seqnum(sd_bus_message *message,
uint64_t *seqnum);
DESCRIPTION
sd_bus_message_get_monotonic_usec() returns the monotonic timestamp of
the time the message was sent. This value is in microseconds since the
CLOCK_MONOTONIC epoch, see clock_gettime(2) for details.
Similarly, sd_bus_message_get_realtime_usec() 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 CLOCK_REALTIME clock.
sd_bus_message_get_seqnum() 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 sd_id128_get_boot(3)) is a suitable globally
unique identifier for bus messages.
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.
These timestamps and the sequence number are attached to each message
by the kernel and cannot be manipulated by the sender.
Note that these timestamps are only available on some bus transports,
and only after support for them has been negotiated with the
sd_bus_negotiate_timestamp(3) call.
RETURN VALUE
On success, these calls return 0 or a positive integer. On failure,
these calls return a negative errno-style error code.
On success, the timestamp or sequence number is returned in the
specified 64-bit unsigned integer variable.
Errors
Returned errors may indicate the following problems:
-EINVAL
A specified parameter is invalid.
-ENODATA
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
sd_bus_negotiate_timestamp(3).
NOTES
Functions described here are available as a shared library, which can
be compiled against and linked to with the libsystemd pkg-config(1)
file.
The code described here uses getenv(3), which is declared to be not
multi-thread-safe. This means that the code calling the functions
described here must not call setenv(3) from a parallel thread. It is
recommended to only do calls to setenv() from an early phase of the
program when no other threads have been started.
SEE ALSO
systemd(1), sd-bus(3), sd_bus_new(3), sd_bus_negotiate_timestamp(3),
clock_gettime(2), sd_id128_get_boot(3)
systemd 254 SD_BUS_MESSAGE_GET_MONOTONIC_USEC(3)
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