SD_JOURNA...TIME_USEC(3)

okay so bestie, welcome to the SD_JOURNA...TIME_USEC(3) page 💖 this is the one where we read timestamps from the current journal entry, and honestly it's giving time-obsessed main character energy. no cap. ✨

🎀 NAME 🎀

• sd_journal_get_realtime_usec
• sd_journal_get_monotonic_usec

— both read timestamps from the current journal entry. periodt. 🫶

🌸 SYNOPSIS 🌸

#include <systemd/sd-journal.h>

int sd_journal_get_realtime_usec(sd_journal *j, uint64_t *usec);

int sd_journal_get_monotonic_usec(sd_journal *j, uint64_t *usec,
                                         sd_id128_t *boot_id);

💅 DESCRIPTION 💅

sd_journal_get_realtime_usec() gets the realtime (wallclock) timestamp of the current journal entry. It takes two arguments: the journal context object and a pointer to a 64-bit unsigned integer to store the timestamp in. The timestamp is in microseconds since the epoch, i.e. CLOCK_REALTIME. literally the wall-clock vibe check. 🕰️

sd_journal_get_monotonic_usec() gets the monotonic timestamp of the current journal entry. It takes three arguments: the journal context object, a pointer to a 64-bit unsigned integer to store the timestamp in, as well as a 128-bit ID buffer to store the boot ID of the monotonic timestamp. The timestamp is in microseconds since boot-up of the specific boot, i.e. CLOCK_MONOTONIC. Since the monotonic clock begins new with every reboot, it only defines a well-defined point in time when used together with an identifier identifying the boot. See sd_id128_get_boot(3) for more information. If the boot ID parameter is passed NULL, the function will fail if the monotonic timestamp of the current entry is not of the current system boot. 🥾

note bestie: these functions will not work before sd_journal_next(3) (or related call) has been called at least once, in order to position the read pointer at a valid entry. like, you gotta move the pointer first, iykyk. 😭

😭 RETURN VALUE 😭

sd_journal_get_realtime_usec() and sd_journal_get_monotonic_usec() returns 0 on success or a negative errno-style error code. If the boot ID parameter was passed NULL and the monotonic timestamp of the current journal entry is not of the current system boot, -ESTALE is returned by sd_journal_get_monotonic_usec(). not me getting an error code, but at least it's a clear one 💀

🧚 NOTES 🧚

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 yes, share the object across time, not simultaneously in two threads, bestie. 🫶

Functions described here are available as a shared library, which can be compiled against and linked to with the libsystemd pkg-config(1) file. slay, link it up. 🔗

👑 HISTORY 👑

sd_journal_get_realtime_usec() and sd_journal_get_monotonic_usec() were added in version 187. iconic vintage behavior, lowkey. 🌈

⭐ SEE ALSO ⭐

systemd(1), sd-journal(3), sd_journal_open(3), sd_journal_next(3), sd_journal_get_data(3), sd_journal_get_seqnum(3), sd_id128_get_boot(3), clock_gettime(2), sd_journal_get_cutoff_realtime_usec(3)

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okay bye bestie — footer source/version is systemd 261.3, and the original footer didn't give a date, so consider this your cute sign-off anyway. mwah 💋✨🎀