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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |NOTES |HISTORY |SEE ALSO |COLOPHON | |
SD_BUS_SEND(3) sd_bus_sendSD_BUS_SEND(3)sd_bus_send, sd_bus_send_to, sd_bus_message_send - Queue a D-Bus message for transfer
#include <systemd/sd-bus.h>int sd_bus_send(sd_bus *bus, sd_bus_message *m, uint64_t *cookie);int sd_bus_send_to(sd_bus *bus, sd_bus_message *m,const char *destination, uint64_t *cookie);int sd_bus_message_send(sd_bus_message *m);
sd_bus_send()queues the bus message objectm for transfer. Ifbus isNULL, the bus thatm is attached to is used.bus only needs to be set when the message is sent to a different bus than the one it is attached to, for example when forwarding messages. If the output parametercookie is notNULL, it is set to the message identifier. This value can later be used to match incoming replies to their corresponding messages. Ifcookie is set toNULLand the message is not sealed,sd_bus_send()assumes the messagem does not expect a reply and adds the necessary headers to indicate this. Note that in most scenarios,sd_bus_send()should not be called directly. Instead, use higher level functions such assd_bus_call_method(3) andsd_bus_reply_method_return(3) which callsd_bus_send()internally.sd_bus_send_to()is a shorthand for sending a message to a specific destination. It's main use case is to simplify sending unicast signal messages (signals that only have a single receiver). It's behavior is similar to callingsd_bus_message_set_destination(3) followed by callingsd_bus_send().sd_bus_send()/sd_bus_send_to()will write the message directly to the underlying transport (e.g. kernel socket buffer) if possible. If the connection is not set up fully yet the message is queued locally. If the transport buffers are congested any unwritten message data is queued locally, too. If the connection has been closed or is currently being closed the call fails.sd_bus_process(3) should be invoked to write out any queued message data to the transport.sd_bus_message_send()is the same assd_bus_send()but without the first and last argument.sd_bus_message_send(m)is equivalent tosd_bus_send(sd_bus_message_get_bus(m), m, NULL).
On success, these functions return a non-negative integer. On failure, they return a negative errno-style error code.Errors Returned errors may indicate the following problems:-EINVAL The input parameterm isNULL. Added in version 246.-EOPNOTSUPP The bus connection does not support sending file descriptors. Added in version 246.-ECHILD The bus connection was allocated in a parent process and is being reused in a child process afterfork(). Added in version 246.-ENOBUFS The bus connection's write queue is full. Added in version 246.-ENOTCONN The input parameterbus isNULLor the bus is not connected. Added in version 246.-ECONNRESET The bus connection was closed while waiting for the response. Added in version 246.-ENOMEM Memory allocation failed. Added in version 246.
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_send()andsd_bus_send_to()were added in version 246.
systemd(1),sd-bus(3),sd_bus_call_method(3),sd_bus_message_set_destination(3),sd_bus_reply_method_return(3),sd_bus_process(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_SEND(3)Pages that refer to this page:sd-bus(3), sd_bus_default(3), sd_bus_emit_signal(3), sd_bus_enqueue_for_read(3), sd_bus_get_n_queued_read(3), sd_bus_message_seal(3), sd_bus_reply_method_error(3), sd_bus_reply_method_return(3), sd_bus_set_watch_bind(3), sd_bus_start(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. | |