sd_event_set_signal_exit - Man Page
Automatically leave event loop on SIGINT and SIGTERM
int sd_event_set_signal_exit(sd_event *event, int b);
sd_event_set_signal_exit() may be used to ensure the event loop terminates once a SIGINT or SIGTERM signal is received. It is a convencience wrapper around invocations of sd_event_add_signal(3) for both signals. The two signals are automatically added to the calling thread's signal mask (if a program is multi-threaded care should be taken to either invoke this function before the first thread is started or to manually block the two signals process-wide first).
If the parameter b is specified as true, the event loop will terminate on SIGINT and SIGTERM. If specified as false, it will no longer. When this functionality is turned off the calling thread's signal mask is restored to match the state before it was turned on, for the two signals. By default the two signals are not handled by the event loop, and Linux' default signal handling for them is in effect.
It's customary for UNIX programs to exit on either of these two signals, hence it's typically a good idea to enable this functionality for the main event loop of a program.
sd_event_set_signal_exit() returns a positive non-zero value when the setting was successfully changed. It returns a zero when the specified setting was already in effect. On failure, it returns a negative errno-style error code.
Returned errors may indicate the following problems:
The event loop has been created in a different process.
The passed event loop object was invalid.
These APIs are implemented as a shared library, which can be compiled and linked to with the libsystemd pkg-config(1) file.
systemd(1), sd-event(3), sd_event_new(3), sd_event_add_signal(3)