'\" t
.TH "SD_BUS_ADD_NODE_ENUMERATOR" "3" "" "systemd 255" "sd_bus_add_node_enumerator"
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.SH "NAME"
sd_bus_add_node_enumerator \- Add a node enumerator for a D\-Bus object path prefix
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-bus\&.h>
.fi
.ft
.HP \w'typedef\ int\ (*sd_bus_node_enumerator_t)('u
.BI "typedef int (*sd_bus_node_enumerator_t)(sd_bus\ *" "bus" ", const\ char\ *" "prefix" ", void\ *" "userdata" ", char\ ***" "ret_nodes" ", sd_bus_error\ *" "ret_error" ");"
.HP \w'int\ sd_bus_add_node_enumerator('u
.BI "int sd_bus_add_node_enumerator(sd_bus\ *" "bus" ", sd_bus_slot\ **" "slot" ", const\ char\ *" "path" ", sd_bus_node_enumerator_t\ " "callback" ", void\ *" "userdata" ");"
.SH "DESCRIPTION"
.PP
\fBsd_bus_add_node_enumerator()\fR
adds a D\-Bus node enumerator for the given path prefix\&. The given callback is called to enumerate all the available objects with the given path prefix when required (e\&.g\&. when
\fBorg\&.freedesktop\&.DBus\&.Introspectable\&.Introspect\fR
or
\fBorg\&.freedesktop\&.DBus\&.ObjectManager\&.GetManagedObjects\fR
are called on a D\-Bus service managed by sd\-bus)\&.
.PP
\fIcallback\fR
is called with the path and userdata pointer registered with
\fBsd_bus_add_node_enumerator()\fR\&. When called, it should store all the child object paths of the given path prefix in
\fIret_nodes\fR
with a NULL terminator item\&. The callback should return a non\-negative value on success\&. If an error occurs, it can either return a negative integer, set
\fIret_error\fR
to a non\-empty error or do both\&. Any errors returned by the callback are encoded as D\-Bus errors and sent back to the caller\&. Errors in
\fIret_error\fR
take priority over negative return values\&.
.PP
Note that a node enumerator callback will only ever be called for a single path prefix and hence, for normal operation,
\fIprefix\fR
can be ignored\&. Also, a node enumerator is only used to enumerate the available child objects under a given prefix\&. To install a handler for a set of dynamic child objects, use
\fBsd_bus_add_fallback_vtable\fR(3)\&.
.PP
When
\fBsd_bus_add_node_enumerator()\fR
succeeds, a slot is created internally\&. If the output parameter
\fIslot\fR
is
\fBNULL\fR, a "floating" slot object is created, see
\fBsd_bus_slot_set_floating\fR(3)\&. Otherwise, a pointer to the slot object is returned\&. In that case, the reference to the slot object should be dropped when the node enumerator is not needed anymore, see
\fBsd_bus_slot_unref\fR(3)\&.
.SH "RETURN VALUE"
.PP
On success,
\fBsd_bus_add_node_enumerator()\fR
returns a non\-negative integer\&. On failure, it returns a negative errno\-style error code\&.
.SS "Errors"
.PP
Returned errors may indicate the following problems:
.PP
\fB\-EINVAL\fR
.RS 4
One of the required parameters is
\fBNULL\fR
or
\fIpath\fR
is not a valid object path\&.
.sp
Added in version 246\&.
.RE
.PP
\fB\-ENOPKG\fR
.RS 4
The bus cannot be resolved\&.
.sp
Added in version 246\&.
.RE
.PP
\fB\-ECHILD\fR
.RS 4
The bus was created in a different process, library or module instance\&.
.sp
Added in version 246\&.
.RE
.PP
\fB\-ENOMEM\fR
.RS 4
Memory allocation failed\&.
.sp
Added in version 246\&.
.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_bus_node_enumerator_t()\fR
and
\fBsd_bus_add_node_enumerator()\fR
were added in version 246\&.
.SH "SEE ALSO"
.PP
\fBsd-bus\fR(3),
\fBbusctl\fR(1),
\fBsd_bus_add_fallback_vtable\fR(3),
\fBsd_bus_slot_unref\fR(3)