x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_BUS_MESSAGE_NEW_SIGNAL(3sd_bus_message_new_signSD_BUS_MESSAGE_NEW_SIGNAL(3)
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 254 SD_BUS_MESSAGE_NEW_SIGNAL(3)
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