SD_BUS_MESSAGE_NEW_SIGNAL(3sd_bus_message_new_signSD_BUS_MESSAGE_NEW_SIGNAL(3)

NAME
       sd_bus_message_new_signal - Create a signal message

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

   Errors
       Returned errors may indicate the following problems:

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

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

       -ENOMEM
           Memory allocation failed.

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

EXAMPLES
       Example 1. Send a simple signal

           /* SPDX-License-Identifier: MIT-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,
                                           "/org/freedesktop/systemd1",
                                           "org.freedesktop.systemd1.Manager",
                                           "UnitFilesChanged");
             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
       systemd(1), sd-bus(3), sd_bus_emit_signal(3)

systemd 252                                       SD_BUS_MESSAGE_NEW_SIGNAL(3)

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