Provided by: libsystemd-dev_251.4-1ubuntu7_amd64 bug


       sd_bus_message_new_signal - Create a signal message


       #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);


       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.


       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.


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


       Example 1. Send a simple signal

           /* SPDX-License-Identifier: CC0-1.0 */

           #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.


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