'\" t
.TH "SD_BUS_GET_N_QUEUED_READ" "3" "" "systemd 261.2" "sd_bus_get_fd"
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.SH "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
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-bus\&.h>
.fi
.ft
.HP \w'int\ sd_bus_get_n_queued_read('u
.BI "int sd_bus_get_n_queued_read(sd_bus\ *" "bus" ", uint64_t\ *" "ret" ");"
.HP \w'int\ sd_bus_get_n_queued_write('u
.BI "int sd_bus_get_n_queued_write(sd_bus\ *" "bus" ", uint64_t\ *" "ret" ");"
.SH "DESCRIPTION"
.PP
\fBsd_bus_get_n_queued_read()\fR
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
\fBsd_bus_process()\fR
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)\&.
.PP
Similarly,
\fBsd_bus_get_n_queued_write()\fR
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
\fBsd_bus_send()\fR
but not yet written to the transport medium\&. The expected arguments are similar to
\fBsd_bus_get_n_queued_read()\fR\&. Here too, use
\fBsd_bus_process()\fR
to reduce the size of the write queue\&. Alternatively, use
\fBsd_bus_flush()\fR
to synchronously write out any pending bus messages until the write queue is empty\&.
.SH "RETURN VALUE"
.PP
On success, these functions return 0 or a positive integer\&. On failure, they return a negative errno\-style error code\&.
.SS "Errors"
.PP
Returned errors may indicate the following problems:
.PP
\fB\-ECHILD\fR
.RS 4
The bus connection was created in a different process, library or module instance\&.
.RE
.SH "NOTES"
.PP
Functions described here are available as a shared library, which can be compiled against and linked to with the
\fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
file\&.
.PP
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\&.
.PP
The code described here uses
\fBgetenv\fR(3), which is declared to be not multi\-thread\-safe\&. This means that the code calling the functions described here must not call
\fBsetenv\fR(3)
from a parallel thread\&. It is recommended to only do calls to
\fBsetenv()\fR
from an early phase of the program when no other threads have been started\&.
.SH "HISTORY"
.PP
\fBsd_bus_get_n_queued_read()\fR
and
\fBsd_bus_get_n_queued_write()\fR
were added in version 238\&.
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1), \fBsd-bus\fR(3), \fBsd_bus_process\fR(3), \fBsd_bus_send\fR(3), \fBsd_bus_flush\fR(3)