sd_bus_emit_signal(3) — Linux manual page


SD_BUS_EMIT_SIGNAL(3)      sd_bus_emit_signal      SD_BUS_EMIT_SIGNAL(3)

NAME         top

       sd_bus_emit_signal, sd_bus_emit_signalv, sd_bus_emit_signal_to,
       sd_bus_emit_signal_tov, sd_bus_emit_interfaces_added,
       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         top

       #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_signal_to(sd_bus *bus, const char *destination,
                                 const char *path,
                                 const char *interface,
                                 const char *member, const char *types,

       int sd_bus_emit_signal_tov(sd_bus *bus, const char *destination,
                                  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);

DESCRIPTION         top

       sd_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_signal_to() and sd_bus_emit_signal_tov() are
       identical to sd_bus_emit_signal() and sd_bus_emit_signalv(),
       except that they can emit the signal to a single destination.
       Give destination as NULL to broadcast the signal.

       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

       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 VALUE         top

       On success, these functions return a non-negative integer. On
       failure, they return a negative errno-style error code.

       Returned errors may indicate the following problems:

           One of the required parameters is NULL or invalid. A reserved
           D-Bus interface was passed as the interface parameter.

           The bus cannot be resolved.

           The bus was created in a different process, library or module

           Memory allocation failed.

           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

NOTES         top

       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

HISTORY         top

       sd_bus_emit_signal(), sd_bus_emit_interfaces_added(),
       sd_bus_emit_properties_changed_strv(), were added in version 221.

       sd_bus_emit_object_added(), and sd_bus_emit_object_removed() were
       added in version 222.

       sd_bus_emit_signalv() was added in version 246.

       sd_bus_emit_signal_to() and sd_bus_emit_signal_tov() were added
       in version 253.

SEE ALSO         top

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

COLOPHON         top

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       This page was obtained from the project's upstream Git repository
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systemd 257~devel                                  SD_BUS_EMIT_SIGNAL(3)

Pages that refer to this page: sd-bus(3)sd_bus_add_object(3)sd_bus_add_object_manager(3)sd_bus_call_method(3)sd_bus_message_new_signal(3)systemd.directives(7)systemd.index(7)