1SD_BUS_MESSAGE_NEW_SIGNAL(3)sd_bus_message_new_signaSlD_BUS_MESSAGE_NEW_SIGNAL(3)
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6 sd_bus_message_new_signal - Create a signal message
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9 #include <systemd/sd-bus.h>
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11 int sd_bus_message_new_signal(sd_bus *bus, sd_bus_message **m,
12 const char *path, const char *interface,
13 const char *member);
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16 The sd_bus_message_new_signal() function creates a new bus message
17 object that encapsulates a D-Bus signal, and returns it in the m output
18 parameter. The signal will be sent to path path, on the interface
19 interface, member member. When this message is sent, no reply is
20 expected. See sd_bus_message_new_method_call(1) for a short description
21 of the meaning of the path, interface, and member parameters.
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24 This function returns 0 if the message object was successfully created,
25 and a negative errno-style error code otherwise.
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27 Errors
28 Returned errors may indicate the following problems:
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30 -EINVAL
31 The output parameter m is NULL.
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33 The path parameter is not a valid D-Bus path ("/an/object/path"),
34 the interface parameter is not a valid D-Bus interface name
35 ("an.interface.name"), or the member parameter is not a valid D-Bus
36 member ("Name").
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38 -ENOTCONN
39 The bus parameter bus is NULL or the bus is not connected.
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41 -ENOMEM
42 Memory allocation failed.
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45 These APIs are implemented as a shared library, which can be compiled
46 and linked to with the libsystemd pkg-config(1) file.
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49 Example 1. Send a simple signal
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51 /* SPDX-License-Identifier: CC0-1.0 */
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53 #include <systemd/sd-bus.h>
54 #define _cleanup_(f) __attribute__((cleanup(f)))
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56 int send_unit_files_changed(sd_bus *bus) {
57 _cleanup_(sd_bus_message_unrefp) sd_bus_message *message = NULL;
58 int r;
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60 r = sd_bus_message_new_signal(bus, &message,
61 "/org/freedesktop/systemd1",
62 "org.freedesktop.systemd1.Manager",
63 "UnitFilesChanged");
64 if (r < 0)
65 return r;
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67 return sd_bus_send(bus, message, NULL);
68 }
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70 This function in systemd sources is used to emit the "UnitFilesChanged"
71 signal when the unit files have been changed.
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74 systemd(1), sd-bus(3), sd_bus_emit_signal(3)
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78systemd 251 SD_BUS_MESSAGE_NEW_SIGNAL(3)