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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | HISTORY | SEE ALSO | COLOPHON |
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SD_BUS_GET_N_QUEUED_READ(3) sd_bus_get_fd SD_BUS_GET_N_QUEUED_READ(3)
sd_bus_get_n_queued_read, sd_bus_get_n_queued_write - Get the
number of pending bus messages in the read and write queues of a
bus connection object
#include <systemd/sd-bus.h>
int sd_bus_get_n_queued_read(sd_bus *bus, uint64_t *ret);
int sd_bus_get_n_queued_write(sd_bus *bus, uint64_t *ret);
sd_bus_get_n_queued_read() may be used to query the number of bus
messages in the read queue of a bus connection object. The read
queue contains all messages read from the transport medium (e.g.
network socket) but not yet processed locally. The function
expects two arguments: the bus object to query, and a pointer to a
64-bit counter variable to write the current queue size to. Use
sd_bus_process() in order to process queued messages, i.e. to
reduce the size of the read queue (as well as, in fact, the write
queue, see below).
Similarly, sd_bus_get_n_queued_write() may be used to query the
number of currently pending bus messages in the write queue of a
bus connection object. The write queue contains all messages
enqueued into the connection with a call such as sd_bus_send() but
not yet written to the transport medium. The expected arguments
are similar to sd_bus_get_n_queued_read(). Here too, use
sd_bus_process() to reduce the size of the write queue.
Alternatively, use sd_bus_flush() to synchronously write out any
pending bus messages until the write queue is empty.
On success, these functions return 0 or a positive integer. On
failure, they return a negative errno-style error code.
Errors
Returned errors may indicate the following problems:
-ECHILD
The bus connection was created in a different process, library
or module instance.
Functions described here are available as a shared library, which
can be compiled against and linked to with the
libsystemd pkg-config(1) file.
All functions listed here are thread-agnostic and only a single
thread may operate on a given object at any given time. Different
threads may access the same object at different times. Multiple
independent objects may be used from different threads in
parallel.
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.
sd_bus_get_n_queued_read() and sd_bus_get_n_queued_write() were
added in version 238.
systemd(1), sd-bus(3), sd_bus_process(3), sd_bus_send(3),
sd_bus_flush(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 2026-08-04. (At that
time, the date of the most recent commit that was found in the
repository was 2026-08-03.) 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 262~devel SD_BUS_GET_N_QUEUED_READ(3)
Pages that refer to this page: sd-bus(3), systemd.directives(7), systemd.index(7)
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HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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