SD_BUS_PROCESS(3)               sd_bus_process               SD_BUS_PROCESS(3)

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
       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_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
       Functions described here are available as a shared library, which can
       be compiled against and linked to with the libsystemd pkg-config(1)
       file.

       The code described here uses getenv(3), which is declared to be not
       multi-thread-safe. This means that the code calling the functions
       described here must not call setenv(3) from a parallel thread. It is
       recommended to only do calls to setenv() from an early phase of the
       program when no other threads have been started.

HISTORY
       sd_bus_process() was added in version 231.

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)

systemd 255                                                  SD_BUS_PROCESS(3)