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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |NOTES |HISTORY |SEE ALSO |COLOPHON | |
SD_BUS_PROCESS(3) sd_bus_processSD_BUS_PROCESS(3)sd_bus_process - Drive the connection
#include <systemd/sd-bus.h>int sd_bus_process(sd_bus *bus, sd_bus_message **ret);
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 intosd_bus_process()again. For that either use the simple, blockingsd_bus_wait(3) call, or hook up the bus connection object to an external or manual event loop usingsd_bus_get_fd(3).sd_bus_process()processes at most one incoming message per call. If the parameterret is notNULLand the call processed a message,*ret is set to this message. The caller owns a reference to this message and should callsd_bus_message_unref(3) when the message is no longer needed. Ifret is notNULLand progress was made, but no message was processed,*ret is set toNULL. Note that only messages not already handled by the various types of registered message handlers (i.e. by filters registered viasd_bus_add_filter(3), object handlers registered viasd_bus_add_object(3), matches registered viasd_bus_add_match(3), and related) will be returned through this parameter. Also note that if such a message handler returns a zero return value (as opposed to some value > 0) an incoming message will not be considered handled, and be passed to other suitable handlers (until one returns > > 0), or returned bysd_bus_process()(in case none returns > 0). If the bus object is connected to ansd-event(3) event loop (withsd_bus_attach_event(3)), it is not necessary to callsd_bus_process()directly as it is invoked automatically when necessary.
If progress was made, a positive integer is returned. If no progress was made, 0 is returned. If an error occurs, a negativeerrno-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 afterfork().-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 bysd_bus_process().
Functions described here are available as a shared library, which can be compiled against and linked to with thelibsystemd pkg-config(1) file. The code described here usesgetenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not callsetenv(3) from a parallel thread. It is recommended to only do calls tosetenv()from an early phase of the program when no other threads have been started.
sd_bus_process()was added in version 221.
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)
This page is part of thesystemd (systemd system and service manager) project. Information about the project can be found at ⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug report for this manual page, see ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This page was obtained from the project's upstream Git repository ⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that time, the date of the most recent commit that was found in the repository was 2025-08-11.) 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 isnot part of the original manual page), send a mail to man-pages@man7.orgsystemd 258~rc2SD_BUS_PROCESS(3)Pages that refer to this page:sd-bus(3), sd_bus_attach_event(3), sd_bus_get_fd(3), sd_bus_get_n_queued_read(3), sd_bus_send(3), sd_bus_start(3), sd_bus_wait(3), systemd.directives(7), systemd.index(7)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |