SD_BUS_EMIT_SIGNAL - Online Linux Manual PageSection : 3
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Source : systemd 250
Note : sd_bus_emit_signal

NAMEsd_bus_emit_signal, sd_bus_emit_signalv, sd_bus_emit_interfaces_added, sd_bus_emit_interfaces_added_strv, sd_bus_emit_interfaces_removed, sd_bus_emit_interfaces_removed_strv, sd_bus_emit_properties_changed, sd_bus_emit_properties_changed_strv, sd_bus_emit_object_added, sd_bus_emit_object_removed − Convenience functions for emitting (standard) D−Bus signals

SYNOPSIS#include <systemd/sd−bus−vtable​.h>int sd_bus_emit_signal(sd_bus *bus, const char *path, const char *interface, const char *member, const char *types, ​.​.​.); int sd_bus_emit_signalv(sd_bus *bus, const char *path, const char *interface, const char *member, const char *types, va_list ap); int sd_bus_emit_interfaces_added(sd_bus *bus, const char *path, const char *interface, ​.​.​.); int sd_bus_emit_interfaces_added_strv(sd_bus *bus, const char *path, const char **interfaces); int sd_bus_emit_interfaces_removed(sd_bus *bus, const char *path, const char *interface, ​.​.​.); int sd_bus_emit_interfaces_removed_strv(sd_bus *bus, const char *path, const char **interfaces); int sd_bus_emit_properties_changed(sd_bus *bus, const char *path, const char *interface, const char *name, ​.​.​.); int sd_bus_emit_properties_changed_strv(sd_bus *bus, const char *path, const char *interface, const char **names); int sd_bus_emit_object_added(sd_bus *bus, const char *path); int sd_bus_emit_object_removed(sd_bus *bus, const char *path);

DESCRIPTIONsd_bus_emit_signal() is a convenience function for initializing a bus message object and emitting the corresponding D−Bus signal​. It combines the sd_bus_message_new_signal(3), sd_bus_message_append(3) and sd_bus_send(3) functions into a single function call​. sd_bus_emit_signalv() is equivalent to sd_bus_message_append(), except that it is called with a "va_list" instead of a variable number of arguments​. sd_bus_emit_interfaces_added() and sd_bus_emit_interfaces_removed() are used to implement the InterfacesAdded and InterfacesRemoved signals of the org​.freedesktop​.DBus​.ObjectManager interface​. They take a path whose interfaces have been modified as an argument and a variable list of interfaces that have been added or removed, respectively​. The final argument passed to sd_bus_emit_interfaces_added() and sd_bus_emit_interfaces_removed() must be NULL​. This allows both functions to safely determine the number of passed interface arguments​. sd_bus_emit_interfaces_added_strv() and sd_bus_emit_interfaces_removed_strv() are identical to their respective counterparts but both take the list of interfaces as a single argument instead of a variable number of arguments​. sd_bus_emit_properties_changed() is used to implement the PropertiesChanged signal of the org​.freedesktop​.DBus​.Properties interface​. It takes an object path, interface and a variable list of property names as its arguments​. The final argument passed to sd_bus_emit_properties_changed() must be NULL​. This allows it to safely determine the number of passed property names​. sd_bus_emit_properties_changed_strv() is identical to sd_bus_emit_properties_changed() but takes the list of property names as a single argument instead of a variable number of arguments​. sd_bus_emit_object_added() and sd_bus_emit_object_removed() are convenience functions for emitting the InterfacesAdded or InterfacesRemoved signals for all interfaces registered on a specific object path, respectively​. This includes any parent fallback vtables if they are not overridden by a more applicable child vtable​. It also includes all the standard D−Bus interfaces implemented by sd−bus itself on any registered object​. Note that sd_bus_emit_interfaces_added(), sd_bus_emit_interfaces_removed(), sd_bus_emit_object_added() and sd_bus_emit_object_removed() require an object manager to have been registered on the given object path or one of its parent object paths using sd_bus_add_object_manager(3)​.

RETURN VALUEOn success, these functions return a non−negative integer​. On failure, they return a negative errno−style error code​.

ErrorsReturned errors may indicate the following problems: −EINVAL One of the required parameters is NULL or invalid​. A reserved D−Bus interface was passed as the interface parameter​. −ENOPKG The bus cannot be resolved​. −ECHILD The bus was created in a different process​. −ENOMEM Memory allocation failed​. −ESRCH One of sd_bus_emit_interfaces_added(), sd_bus_emit_interfaces_removed(), sd_bus_emit_object_added() or sd_bus_emit_object_removed() was called on an object without an object manager registered on its own object path or one of its parent object paths​. See the man pages of sd_bus_message_new_signal(3), sd_bus_message_append(3) and sd_bus_send(3) for more possible errors​.

NOTESThese APIs are implemented as a shared library, which can be compiled and linked to with the libsystemd ​pkg-config(1) file​.

SEE ALSOsd-bus(3), busctl(1), sd_bus_message_new_signal(3), sd_bus_message_append(3), sd_bus_send(3), sd_bus_call_method(3)
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