Manpages - sd_bus_message_new_signal.3
Table of Contents
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
#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)