Provided by: libsystemd-dev_237-3ubuntu10.57_amd64 bug


       sd_event_add_signal, sd_event_source_get_signal, sd_event_signal_handler_t - Add a UNIX
       process signal event source to an event loop


       #include <systemd/sd-event.h>

       typedef struct sd_event_source sd_event_source;

       typedef int (*sd_event_signal_handler_t)(sd_event_source *s,
                                                const struct signalfd_siginfo *si,
                                                void *userdata);

       int sd_event_add_signal(sd_event *event, sd_event_source **source, int signal,
                               sd_event_signal_handler_t handler, void *userdata);

       int sd_event_source_get_signal(sd_event_source *source);


       sd_event_add_signal() adds a new UNIX process signal event source to an event loop. The
       event loop object is specified in the event parameter, and the event source object is
       returned in the source parameter. The signal parameter specifies the numeric signal to be
       handled (see signal(7)). The handler parameter must reference a function to call when the
       signal is received or be NULL. The handler function will be passed the userdata pointer,
       which may be chosen freely by the caller. The handler also receives a pointer to a
       signalfd_siginfo structure containing information about the received signal. See
       signalfd(2) for further information.

       Only a single handler may be installed for a specific signal. The signal will be unblocked
       by this call, and must be blocked before this function is called in all threads (using
       sigprocmask(2)). If the handler is not specified (handler is NULL), a default handler
       which causes the program to exit cleanly will be used.

       By default, the event source is enabled permanently (SD_EVENT_ON), but this may be changed
       with sd_event_source_set_enabled(3). If the handler function returns a negative error
       code, it will be disabled after the invocation, even if the SD_EVENT_ON mode was requested

       To destroy an event source object use sd_event_source_unref(3), but note that the event
       source is only removed from the event loop when all references to the event source are
       dropped. To make sure an event source does not fire anymore, even if it is still
       referenced, disable the event source using sd_event_source_set_enabled(3) with

       If the second parameter of sd_event_add_signal() is NULL no reference to the event source
       object is returned. In this case the event source is considered "floating", and will be
       destroyed implicitly when the event loop itself is destroyed.

       sd_event_source_get_signal() returns the configured signal number of an event source
       created previously with sd_event_add_signal(). It takes the event source object as the
       source parameter.


       On success, these functions return 0 or a positive integer. On failure, they return a
       negative errno-style error code.


       Returned errors may indicate the following problems:

           Not enough memory to allocate an object.

           An invalid argument has been passed.

           A handler is already installed for this signal or the signal was not blocked

           The event loop is already terminated.

           The event loop has been created in a different process.

           The passed event source is not a signal event source.


       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_now(3), sd_event_add_io(3),
       sd_event_add_time(3), sd_event_add_child(3), sd_event_add_defer(3),
       sd_event_source_set_enabled(3), sd_event_source_set_description(3),
       sd_event_source_set_userdata(3), signal(7), signalfd(2)