SD_BUS_...NIC_USEC(3)

💅 sd_bus_message_get_monotonic_usec, sd_bus_message_get_realtime_usec, sd_bus_message_get_seqnum 💅

okay so bestie, this is the SD_BUS_...NIC_USEC(3) manual page — yes, the manual name is giving dramatic ellipsis main-character energy, and we're obsessed ✨. It's all about grabbing the sender timestamps and the sequence number attached to a bus message. No cap, these are kernel-provided receipts 👑

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🌸 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 — check clock_gettime(2) if you want the whole lore on that clock. It's giving “when did this happen on the monotonic timeline” energy ⏱️.

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. So yes, bestie, it's that classic Unix-epoch wallclock vibe 🌸.

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. Iconic little combo, honestly 👑

⚠️ 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. So don't assume the receipt list is sorted, bestie — order can be a little chaotic 💀.

These timestamps and the sequence number are attached to each message by the kernel and cannot be manipulated by the sender. Kernel says no take-backs, no edits, no makeup filter 🔥.

⚠️ 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. If you didn't negotiate, it's not gonna manifest for you, periodt 💅.

👑 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. Cute, clean, 64 bits of truth 💖.

😭 Errors 😭

Returned errors may indicate the following problems:

• -EINVAL — a specified parameter is invalid. Bestie, check your args 🙈.
• -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). It's giving “the metadata said no” 💀.

🧚 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. Link it, love it, live it 🫶.

All functions listed here are thread-agnostic and only a single thread may operate on a given object at any given time. Different threads may access the same object at different times. Multiple independent objects may be used from different threads in parallel. So, like, object-level boundaries are the whole assignment — don't have multiple threads on the same object at the same time 🌸.

⚠️ 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. Early-phase setenv() only, please — no parallel-thread chaos 💅.

⭐ HISTORY ⭐

sd_bus_message_get_monotonic_usec(), sd_bus_message_get_realtime_usec(), and sd_bus_message_get_seqnum() were added in version 209. Vintage but still slaying 👑.

🌈 SEE ALSO 🌈

systemd(1), sd-bus(3), sd_bus_new(3), sd_bus_negotiate_timestamp(3), clock_gettime(2), sd_id128_get_boot(3)

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mwah 💋 — signing off with the footer facts: systemd 261.3, page tag SD_BUS_...NIC_USEC(3) — and no date is printed in this footer, so I'm not making one up, bestie 🙈🫶