'\" t
.TH "SD_VARLINK_SEND" "3" "" "systemd 258" "sd_varlink_send"
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.SH "NAME"
sd_varlink_send, sd_varlink_sendb, sd_varlink_sendbo \- Enqueues a Varlink method call, not expecting a reply
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-varlink\&.h>
.fi
.ft
.HP \w'int\ sd_varlink_send('u
.BI "int sd_varlink_send(sd_varlink\ *" "link" ", const\ char\ *" "method" ", sd_json_variant\ *" "parameters" ");"
.HP \w'int\ sd_varlink_sendb('u
.BI "int sd_varlink_sendb(sd_varlink\ *" "link" ", const\ char\ *" "method" ", \&...);"
.HP \w'int\ sd_varlink_sendbo('u
.BI "int sd_varlink_sendbo(sd_varlink\ *" "link" ", const\ char\ *" "method" ", \&...);"
.SH "DESCRIPTION"
.PP
\fBsd_varlink_send()\fR
submits a method call via a Varlink connection\&. It takes the Varlink connection object, a method name as string parameter, and a JSON object containing the parameters to pass as function parameters\&. This call is asynchronous: the message will not be delivered immediately but only once
\fBsd_varlink_process\fR(3)
is invoked (which will happen automatically in one of the following event loop iterations if the Varlink connection is attached to an even loop)\&.
.PP
\fBsd_varlink_sendb()\fR
is similar to
\fBsd_varlink_send()\fR, but instead of expecting a fully constructed
\fBsd_json_variant\fR
object carrying the parameters, this object is constructed on\-the\-fly directly from the parameter list, in a style identical to
\fBsd_json_build\fR(3)\&.
.PP
\fBsd_varlink_sendbo()\fR
is identical to
\fBsd_varlink_sendb()\fR, but an enclosing object is implicitly added, so that the parameter list is expected to consist of field pairs only\&. For details about the expected argument list, see
\fBsd_json_buildo\fR(3)\&.
.PP
Use
\fBsd_varlink_send()\fR,
\fBsd_varlink_sendb()\fR
and
\fBsd_varlink_sendbo()\fR
only if no method call results are required, as they neither provide return parameters nor success/failure information\&. Use
\fBsd_varlink_call\fR(3)
(and related calls) to submit a method call synchronously, returning the server\*(Aqs response\&.
.SH "RETURN VALUE"
.PP
On success,
\fBsd_varlink_send()\fR,
\fBsd_varlink_sendb()\fR
and
\fBsd_varlink_sendbo()\fR
return a non\-negative integer\&. On failure, they return a negative errno\-style error code\&.
.SS "Errors"
.PP
Returned errors may indicate the following problems:
.PP
\fB\-EINVAL\fR
.RS 4
An argument is invalid\&.
.RE
.PP
\fB\-ENOMEM\fR
.RS 4
Memory allocation failed\&.
.RE
.PP
\fB\-ENOTCONN\fR
.RS 4
The Varlink connection object is not connected\&.
.RE
.PP
\fB\-EBUSY\fR
.RS 4
The Varlink connection object is already used for other purposes, i\&.e\&. executing a method call or similar\&.
.RE
.PP
\fB\-ENOBUFS\fR
.RS 4
The internal limit of queued messages for the Varlink connection has been reached\&. This limit is set very high, and hitting it typically indicates that the Varlink connection object is stalled \(em possibly because
\fBsd_varlink_process()\fR
has not been called regularly enough, or because the peer is not processing any queued messages\&. This limit is a safety precaution to ensure a stalled peer will not result in unbounded memory allocations on the client side\&.
.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
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_varlink_send()\fR,
\fBsd_varlink_sendb()\fR,
\fBsd_varlink_sendbo()\fR
were added in version 257\&.
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1), \fBsd-varlink\fR(3), \fBsd_varlink_call\fR(3), \fBsd_varlink_build\fR(3)