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 user 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 a 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)