sd_bus_message_new_signal(3) — Linux manual page



NAME         top

       sd_bus_message_new_signal - Create a signal message

SYNOPSIS         top

       #include <systemd/sd-bus.h>

       int sd_bus_message_new_signal(sd_bus *bus, sd_bus_message **m,
                                     const char *path,
                                     const char *interface,
                                     const char *member);

DESCRIPTION         top

       The sd_bus_message_new_signal() function creates a new bus
       message object that encapsulates a D-Bus signal, and returns it
       in the m output parameter. The signal will be sent to path path,
       on the interface interface, member member. When this message is
       sent, no reply is expected. See sd_bus_message_new_method_call(1)
       for a short description of the meaning of the path, interface,
       and member parameters.

RETURN VALUE         top

       This function returns 0 if the message object was successfully
       created, and a negative errno-style error code otherwise.

       Returned errors may indicate the following problems:

           The output parameter m is NULL.

           The path parameter is not a valid D-Bus path
           ("/an/object/path"), the interface parameter is not a valid
           D-Bus interface name (""), or the member
           parameter is not a valid D-Bus member ("Name").

           The bus parameter bus is NULL or the bus is not connected.

           Memory allocation failed.

NOTES         top

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

EXAMPLES         top

       Example 1. Send a simple signal

           #include <systemd/sd-bus.h>
           #define _cleanup_(f) __attribute__((cleanup(f)))

           int send_unit_files_changed(sd_bus *bus) {
             _cleanup_(sd_bus_message_unrefp) sd_bus_message *message = NULL;
             int r;

             r = sd_bus_message_new_signal(bus, &message,
             if (r < 0)
               return r;

             return sd_bus_send(bus, message, NULL);

       This function in systemd sources is used to emit the
       "UnitFilesChanged" signal when the unit files have been changed.

SEE ALSO         top

       systemd(1), sd-bus(3), sd_bus_emit_signal(3)

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨⟩.  If you have
       a bug report for this manual page, see
       This page was obtained from the project's upstream Git repository
       ⟨⟩ on 2020-12-18.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2020-12-18.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
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       (which is not part of the original manual page), send a mail to

systemd 247                                 SD_BUS_MESSAGE_NEW_SIGNAL(3)

Pages that refer to this page: sd-bus(3)sd_bus_emit_signal(3)sd_bus_message_get_type(3)sd_bus_message_new(3)systemd.directives(7)systemd.index(7)