SD_BUS_MESSAGE_NEW_SIGNAL(3)

  .SH "NAME" sd_bus_message_new_signal - Create a signal message
  .SH "SYNOPSIS"

#include <systemd/sd-bus.h>

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

  .SH "DESCRIPTION"

    .PP 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_call(1) for a short description of the meaning of the path, interface, and member parameters.

  .SH "RETURN VALUE"

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

  .SH "ERRORS"

    .PP Returned errors may indicate the following problems:

      .PP -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).
          .RE
          .PP -ENOTCONN

                The bus parameter bus is NULL or the bus is not connected.
              .RE
              .PP -ENOMEM

                    Memory allocation failed.
                  .RE

              .SH "NOTES"

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

                .PP 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,
                                                "/org/freedesktop/systemd1",
                                                "org.freedesktop.systemd1.Manager",
                                                "UnitFilesChanged");
                  if (r < 0)
                    return r;
                  return sd_bus_send(bus, message, NULL);
                }

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

              .SH "SEE ALSO"

                .PP systemd(1), sd-bus(3)