sd_bus_process(3) — Linux manual page


SD_BUS_PROCESS(3)              sd_bus_process              SD_BUS_PROCESS(3)

NAME         top

       sd_bus_process - Drive the connection

SYNOPSIS         top

       #include <systemd/sd-bus.h>

       int sd_bus_process(sd_bus *bus, sd_bus_message **ret);

DESCRIPTION         top

       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_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         top

       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.

       Returned errors may indicate the following problems:

           An invalid bus object was passed.

           The bus connection was allocated in a parent process and is being
           reused in a child process after fork().

           The bus connection has been terminated already.

           The bus connection has been terminated just now.

           This function is already being called, i.e.  sd_bus_process() has
           been called from a callback function that itself was called by

NOTES         top

       These APIs are implemented as a shared library, which can be compiled
       and linked to with the libsystemd pkg-config(1) file.

SEE ALSO         top

       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)

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug
       report for this manual page, see
       ⟨⟩.  This
       page was obtained from the project's upstream Git repository
       ⟨⟩ on 2020-09-18.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-09-18.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
       more up-to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not part
       of the original manual page), send a mail to

systemd 246                                                SD_BUS_PROCESS(3)

Pages that refer to this page: sd-bus(3)sd_bus_attach_event(3)sd_bus_detach_event(3)sd_bus_get_event(3)sd_bus_get_events(3)sd_bus_get_fd(3)sd_bus_get_n_queued_read(3)sd_bus_get_n_queued_write(3)sd_bus_get_timeout(3)sd_bus_set_fd(3)sd_bus_start(3)sd_bus_wait(3)30-systemd-environment-d-generator(7)systemd.directives(7)systemd.index(7)