SD_BUS_MESSAGE_NEW_SIGNAL(3)                         sd_bus_message_new_signal

NAME
       sd_bus_message_new_signal, sd_bus_message_new_signal_to - 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);

       int sd_bus_message_new_signal_to(sd_bus *bus, sd_bus_message **m,
                                        const char *destination,
                                        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.

       sd_bus_message_new_signal_to() is a shorthand for creating a new bus
       message to a specific destination. It's behavior is similar to calling
       sd_bus_message_new_signal() followed by calling
       sd_bus_message_set_destination(3).

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
       Functions described here are available as a shared library, which can
       be compiled against and linked to with the libsystemd pkg-config(1)
       file.

       The code described here uses getenv(3), which is declared to be not
       multi-thread-safe. This means that the code calling the functions
       described here must not call setenv(3) from a parallel thread. It is
       recommended to only do calls to setenv() from an early phase of the
       program when no other threads have been started.

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)
       sd_bus_message_set_destination(3)

systemd 255                                       SD_BUS_MESSAGE_NEW_SIGNAL(3)