sd_bus_emit_signal

systemd
sd_bus_emit_signal 3
sd_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

    #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

## Description

`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_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 Value

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

### Errors

Returned 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.

## See Also

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