NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | NOTES | SEE ALSO | COLOPHON

SD_EVENT_ADD_SIGNAL(3)       sd_event_add_signal      SD_EVENT_ADD_SIGNAL(3)

NAME         top

       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

SYNOPSIS         top

       #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);

DESCRIPTION         top

       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
       before.

       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
       SD_EVENT_OFF.

       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.

RETURN VALUE         top

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

ERRORS         top

       Returned errors may indicate the following problems:

       -ENOMEM
           Not enough memory to allocate an object.

       -EINVAL
           An invalid argument has been passed.

       -EBUSY
           A handler is already installed for this signal or the signal was
           not blocked previously.

       -ESTALE
           The event loop is already terminated.

       -ECHILD
           The event loop has been created in a different process.

       -EDOM
           The passed event source is not a signal event source.

NOTES         top

       These APIs are implemented as a shared library, which can be compiled
       and linked to with the libsystemd pkg-config(1) file.

SEE ALSO         top

       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)

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a bug
       report for this manual page, see 
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.  This
       page was obtained from the project's upstream Git repository 
       ⟨https://github.com/systemd/systemd.git⟩ on 2017-07-05.  If you dis‐
       cover any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page, or
       you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

systemd 234                                           SD_EVENT_ADD_SIGNAL(3)

Pages that refer to this page: sd-event(3)sd_event_add_child(3)sd_event_add_defer(3)sd_event_add_io(3)sd_event_add_time(3)sd_event_new(3)sd_event_run(3)sd_event_set_watchdog(3)sd_event_source_get_event(3)sd_event_source_get_pending(3)sd_event_source_set_description(3)sd_event_source_set_enabled(3)sd_event_source_set_prepare(3)sd_event_source_set_priority(3)sd_event_source_set_userdata(3)sd_event_source_unref(3)sd_event_wait(3)systemd.directives(7)systemd.index(7)