When exiting is requested the event loop will stop listening for and dispatching regular event sources. Instead it will proceed with executing only event sources registered with sd_event_add_exit(3) in the order defined by their priority. After all exit event sources have been dispatched the event loop is terminated.
If sd_event_exit() is invoked a second time while the event loop is still processing exit event sources, the exit code stored in the event loop object is updated, but otherwise no further operation is executed.
sd_event_get_exit_code() may be used to query the exit code passed into sd_event_exit() earlier.
While the full positive and negative integer ranges may be used for the exit code, care should be taken not pick exit codes that conflict with regular exit codes returned by sd_event_loop(), if these exit codes shall be distinguishable.
Note that for most event source types passing the callback pointer as NULL in the respective constructor call (i.e. in sd_event_add_time(3), sd_event_add_signal(3), ...) has the effect of sd_event_exit() being invoked once the event source triggers, with the specified userdata pointer cast to an integer as the exit code parameter. This is useful to automatically terminate an event loop after some condition, such as a time-out or reception of SIGTERM or similar. See the documentation for the respective constructor call for details.
Returned errors may indicate the following problems:
These APIs are implemented as a shared library, which can be compiled and linked to with the libsystemd pkg-config(1) file.