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 221.

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)