sd_event_run(3) — Linux manual page


SD_EVENT_RUN(3)               sd_event_run               SD_EVENT_RUN(3)

NAME         top

       sd_event_run, sd_event_loop - Run an event loop

SYNOPSIS         top

       #include <systemd/sd-event.h>

       int sd_event_run(sd_event *event, uint64_t usec);

       int sd_event_loop(sd_event *event);

DESCRIPTION         top

       sd_event_run() may be used to run a single iteration of the event
       loop specified in the event parameter. The function waits until
       an event to process is available, and dispatches the registered
       handler for it. The usec parameter specifies the maximum time (in
       microseconds) to wait for an event. Use (uint64_t) -1 to specify
       an infinite timeout.

       sd_event_loop() invokes sd_event_run() in a loop, thus
       implementing the actual event loop. The call returns as soon as
       exiting was requested using sd_event_exit(3).

       The event loop object event is created with sd_event_new(3).
       Events sources to wait for and their handlers may be registered
       with sd_event_add_io(3), sd_event_add_time(3),
       sd_event_add_signal(3), sd_event_add_child(3),
       sd_event_add_defer(3), sd_event_add_post(3) and

       For low-level control of event loop execution, use
       sd_event_prepare(3), sd_event_wait(3) and sd_event_dispatch(3)
       which are wrapped by sd_event_run(). Along with
       sd_event_get_fd(3), these functions allow integration of an
       sd-event(3) event loop into foreign event loop implementations.

RETURN VALUE         top

       On failure, these functions return a negative errno-style error
       code.  sd_event_run() returns a positive, non-zero integer if an
       event source was dispatched, and zero when the specified timeout
       hit before an event source has seen any event, and hence no event
       source was dispatched.  sd_event_loop() returns the exit code
       specified when invoking sd_event_exit().

       Returned errors may indicate the following problems:

           The event parameter is invalid or NULL.

           The event loop object is not in the right state (see
           sd_event_prepare(3) for an explanation of possible states).

           The event loop is already terminated.

           The event loop has been created in a different process,
           library or module instance.

       Other errors are possible, too.

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_run() and sd_event_loop() were added in version 220.

SEE ALSO         top

       systemd(1), sd-event(3), sd_event_new(3), sd_event_add_io(3),
       sd_event_add_time(3), sd_event_add_signal(3),
       sd_event_add_child(3), sd_event_add_inotify(3),
       sd_event_add_defer(3), sd_event_exit(3), sd_event_get_fd(3),
       sd_event_wait(3), GLib Main Event Loop[1]

NOTES         top

        1. GLib Main Event Loop

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
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       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
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       (which is not part of the original manual page), send a mail to

systemd 255                                              SD_EVENT_RUN(3)

Pages that refer to this page: sd-event(3)sd_event_exit(3)sd_event_new(3)sd_event_wait(3)systemd.directives(7)systemd.index(7)