sd_bus_get_n_queued

Name

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

Synopsis

#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)`;

Description¶

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.

Return Value¶

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.

Notes¶

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.

History¶

sd_bus_get_n_queued_read() and sd_bus_get_n_queued_write() were added in version 238.