Manpages - sd_bus_process.3
Table of Contents
NAME
sd_bus_process - Drive the connection
SYNOPSIS
#include <systemd/sd-bus.h>
int sd_bus_process(sd_bus **/bus/, sd_bus_message **/ret/);*
DESCRIPTION
sd_bus_process() drives the connection between the client and the message bus. That is, it handles connecting, authentication, and message processing. 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 synchronously poll for I/O events before calling into sd_bus_process() again. For that either use the simple, synchronous *sd_bus_wait*(3) call, or hook up the bus connection object to an external or manual event loop using *sd_bus_get_fd*(3).
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_unref*(3) when the message is no longer needed. If ret is not *NULL, progress was made, but no message was processed, *ret is set to NULL.
If the bus object is connected to an sd-event*(3) event loop (with *sd_bus_attach_event*(3)), it is not necessary to call *sd_bus_process() directly as it is invoked automatically when necessary.
RETURN VALUE
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.
Errors
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().
NOTES
These APIs are implemented as a shared library, which can be compiled and linked to with the libsystemd *pkg-config*(1) file.
SEE ALSO
*systemd*(1), *sd-bus*(3), *sd_bus_wait*(3), *sd_bus_get_fd*(3), *sd_bus_message_unref*(3), *sd-event*(3), *sd_bus_attach_event*(3)