oracular (3) sd_bus_process.3.gz

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)