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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | SEE ALSO | COLOPHON |
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SD_BUS_SEND(3) sd_bus_send SD_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 object m for transfer. If
bus is NULL, the bus that m is attached to is used. bus only
needs to be set when the message is sent to a different bus than
the one it's attached to, for example when forwarding messages.
If the output parameter cookie is not NULL, it is set to the
message identifier. This value can later be used to match
incoming replies to their corresponding messages. If cookie is
set to NULL and the message is not sealed, sd_bus_send() assumes
the message m doesn't 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 as
sd_bus_call_method(3) and sd_bus_reply_method_return(3) which
call sd_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 calling
sd_bus_message_set_destination(3) followed by calling
sd_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 as sd_bus_send() but without
the first and last argument. sd_bus_message_send(m) is
equivalent to sd_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 parameter m is NULL.
-EOPNOTSUPP
The bus connection does not support sending file descriptors.
-ECHILD
The bus connection was allocated in a parent process and is
being reused in a child process after fork().
-ENOBUFS
The bus connection's write queue is full.
-ENOTCONN
The input parameter bus is NULL or the bus is not connected.
-ECONNRESET
The bus connection was closed while waiting for the response.
-ENOMEM
Memory allocation failed.
These APIs are implemented as a shared library, which can be
compiled and linked to with the libsystemd pkg-config(1) file.
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 the systemd (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 2022-12-17. (At that
time, the date of the most recent commit that was found in the
repository was 2022-12-16.) 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
man-pages@man7.org
systemd 252 SD_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_set_watch_bind(3), sd_bus_start(3), systemd.directives(7), systemd.index(7)
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