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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | HISTORY | SEE ALSO | COLOPHON |
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SD_BUS...IC_USEC(3) sd_bus_message_get_monotonic_usecSD_BUS...IC_USEC(3)
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
#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);
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.
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).
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.
sd_bus_message_get_monotonic_usec(),
sd_bus_message_get_realtime_usec(), and
sd_bus_message_get_seqnum() were added in version 209.
systemd(1), sd-bus(3), sd_bus_new(3),
sd_bus_negotiate_timestamp(3), clock_gettime(2),
sd_id128_get_boot(3)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have
a bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 257~devel SD_BUS...IC_USEC(3)
Pages that refer to this page: sd-bus(3), sd_bus_negotiate_fds(3), systemd.directives(7), systemd.index(7)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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