NAME

       sd_event_run, sd_event_loop - Run an event loop

SYNOPSIS

       #include <systemd/sd-event.h>

       int sd_event_run(sd_event *event, uint64_t usec);

       int sd_event_loop(sd_event *event);

DESCRIPTION

       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 sd_event_add_exit(3).

       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

       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().

   Errors
       Returned errors may indicate the following problems:

       -EINVAL
           The event parameter is invalid or NULL.

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

       -ESTALE
           The event loop is already terminated.

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

       Other errors are possible, too.

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.

       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.

HISTORY

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

SEE ALSO

       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

        1. GLib Main Event Loop
           https://developer.gnome.org/glib/unstable/glib-The-Main-Event-Loop.html