systemd sd_bus_process 3 sd_bus_process Drive the connection #include <systemd/sd-bus.h> int sd_bus_process sd_bus *bus sd_bus_message **ret sd_bus_process() drives the connection between the client and the message bus. That is, it handles connecting, authentication, and processing of messages. When invoked, pending I/O work is executed, and queued incoming messages are dispatched to registered callbacks. Each time it is invoked a single operation is executed. It returns zero when no operations were pending and positive if a message was processed. When zero is returned the caller should poll for I/O events before calling into sd_bus_process() again. For that either use the simple, blocking sd_bus_wait3 call, or hook up the bus connection object to an external or manual event loop using sd_bus_get_fd3. sd_bus_process() processes at most one incoming message per call. If the parameter ret is not NULL and the call processed a message, *ret is set to this message. The caller owns a reference to this message and should call sd_bus_message_unref3 when the message is no longer needed. If ret is not NULL and progress was made, but no message was processed, *ret is set to NULL. Note that only messages not already handled by the various types of registered message handlers (i.e. by filters registered via sd_bus_add_filter3, object handlers registered via sd_bus_add_object3, matches registered via sd_bus_add_match3, and related) will be returned through this parameter. Also note that if such a message handler returns a zero return value (as opposed to some value > 0) an incoming message will not be considered handled, and be passed to other suitable handlers (until one returns > > 0), or returned by sd_bus_process() (in case none returns > 0). If the bus object is connected to an sd-event3 event loop (with sd_bus_attach_event3), it is not necessary to call sd_bus_process() directly as it is invoked automatically when necessary. If progress was made, a positive integer is returned. If no progress was made, 0 is returned. If an error occurs, a negative errno-style error code is returned. Returned errors may indicate the following problems: -EINVAL An invalid bus object was passed. -ECHILD The bus connection was allocated in a parent process and is being reused in a child process after fork(). -ENOTCONN The bus connection has been terminated already. -ECONNRESET The bus connection has been terminated just now. -EBUSY This function is already being called, i.e. sd_bus_process() has been called from a callback function that itself was called by sd_bus_process(). sd_bus_process() was added in version 221. systemd1 sd-bus3 sd_bus_wait3 sd_bus_get_fd3 sd_bus_message_unref3 sd-event3 sd_bus_attach_event3