systemd sd_bus_message_new_signal 3 sd_bus_message_new_signal sd_bus_message_new_signal_to Create a signal message #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 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_call1 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_destination3. This function returns 0 if the message object was successfully created, and a negative errno-style error code otherwise. 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. This function in systemd sources is used to emit the UnitFilesChanged signal when the unit files have been changed. systemd1 sd-bus3 sd_bus_emit_signal3 sd_bus_message_set_destination3