'\" t
.TH "SD_BUS_ADD_MATCH" "3" "" "systemd 232" "sd_bus_add_match"
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.SH "NAME"
sd_bus_add_match \- Add a match rule for message dispatching
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-bus\&.h>
.fi
.ft
.HP \w'int\ sd_bus_add_match('u
.BI "int sd_bus_add_match(sd_bus\ *" "bus" ", sd_bus_slot\ **" "slot" ", const\ char\ *" "match" ", sd_bus_message_handler_t\ " "callback" ", void\ *" "userdata" ");"
.HP \w'typedef\ int\ (*sd_bus_message_handler_t)('u
.BI "typedef int (*sd_bus_message_handler_t)(sd_bus_message\ *" "m" ", void\ *" "userdata" ", sd_bus_error\ *" "ret_error" ");"
.SH "DESCRIPTION"
.PP
\fBsd_bus_add_match()\fR
adds a match rule used to dispatch incoming messages\&. The syntax of the rule passed in
\fImatch\fR
is described in the
\m[blue]\fBD\-Bus Specification\fR\m[]\&\s-2\u[1]\d\s+2\&.
.PP
The message
\fIm\fR
passed to the callback is only borrowed, that is, the callback should not call
\fBsd_bus_message_unref\fR(3)
on it\&. If the callback wants to hold on to the message beyond the lifetime of the callback, it needs to call
\fBsd_bus_message_ref\fR(3)
to create a new reference\&.
.PP
If an error occurs during the callback invocation, the callback should return a negative error number\&. If it wants other callbacks that match the same rule to be called, it should return 0\&. Otherwise it should return a positive integer\&.
.SH "RETURN VALUE"
.PP
On success,
\fBsd_bus_add_match()\fR
returns 0 or a positive integer\&. On failure, it returns a negative errno\-style error code\&.
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1),
\fBsd-bus\fR(3),
.SH "NOTES"
.IP " 1." 4
D-Bus Specification
.RS 4
\%https://dbus.freedesktop.org/doc/dbus-specification.html
.RE