sd_bus_set_sender, sd_bus_get_sender — Configure default sender for outgoing messages
#include <systemd/sd-bus.h>
int sd_bus_set_sender( | sd_bus *bus, | 
const char* name); | 
int sd_bus_get_sender( | sd_bus *bus, | 
const char** name); | 
sd_bus_set_sender() configures the default sender service name to use for outgoing
    messages. The service name specified in the name parameter is set on all outgoing messages
    that are sent on the connection and have no sender set yet, for example through
    sd_bus_message_set_sender(3). Note
    that this function is only supported on direct connections, i.e. not on connections to a bus broker as the broker
    will fill in the sender service name automatically anyway. By default no sender name is configured, and hence
    messages are sent without sender field set. If the name parameter is specified as
    NULL the default sender service name is cleared, returning to the default state if a default
    sender service name was set before. If passed as non-NULL the specified name must be a valid
    unique or well-known service name.
sd_bus_get_sender() may be used to query the current default service name for outgoing
    messages.
On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style error code.
These APIs are implemented as a shared
  library, which can be compiled and linked to with the
  libsystemd pkg-config(1)
  file.