sd_event_now(3) — Linux manual page


SD_EVENT_NOW(3)               sd_event_now               SD_EVENT_NOW(3)

NAME         top

       sd_event_now - Retrieve current event loop iteration timestamp

SYNOPSIS         top

       #include <systemd/sd-event.h>

       int sd_event_now(sd_event *event, clockid_t clock,
                        uint64_t *usec);

DESCRIPTION         top

       sd_event_now() returns the time when the most recent event loop
       iteration began. A timestamp is taken right after returning from
       the event sleep, and before dispatching any event sources. The
       event parameter specifies the event loop object to retrieve the
       timestamp from. The clock parameter specifies the clock to
       retrieve the timestamp for, and is one of CLOCK_REALTIME (or
       CLOCK_BOOTTIME (or equivalently CLOCK_BOOTTIME_ALARM), see
       clock_gettime(2) for more information on the various clocks. The
       retrieved timestamp is stored in the usec parameter, in μs since
       the clock's epoch. If this function is invoked before the first
       event loop iteration, the current time is returned, as reported
       by clock_gettime(). To distinguish this case from a regular
       invocation the return value will be positive, and zero when the
       returned timestamp refers to an actual event loop iteration.

RETURN VALUE         top

       If the first event loop iteration has not run yet sd_event_now()
       writes current time to usec and returns a positive return value.
       Otherwise, it will write the requested timestamp to usec and
       return 0. On failure, the call returns a negative errno-style
       error code.

       Returned values may indicate the following problems:

           An invalid parameter was passed.

           Unsupported clock type.

           The event loop object was created in a different process,
           library or module instance.

NOTES         top

       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

HISTORY         top

       sd_event_now() was added in version 229.

SEE ALSO         top

       systemd(1), sd-event(3), sd_event_new(3), sd_event_add_time(3),

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨⟩.  If you have
       a bug report for this manual page, see
       This page was obtained from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-22.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
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       (which is not part of the original manual page), send a mail to

systemd 255                                              SD_EVENT_NOW(3)

Pages that refer to this page: sd-event(3)sd_event_add_child(3)sd_event_add_defer(3)sd_event_add_inotify(3)sd_event_add_io(3)sd_event_add_signal(3)sd_event_add_time(3)systemd.directives(7)systemd.index(7)