---
name: "sd_bus_add_node_enumerator"
section: "3"
platform: "linux"
package: "systemd-libs"
version: "262.1-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/sd_bus_add_node_enumerator"
---

# sd\_bus\_add\_node\_enumerator(3)

Add a node enumerator for a D-Bus object path prefix

## NAME

sd\_bus\_add\_node\_enumerator - Add a node enumerator for a D-Bus object path prefix

## SYNOPSIS

```
#include <systemd/sd-bus.h>
```

**typedef int (\*sd\_bus\_node\_enumerator\_t)(sd\_bus \****bus***, const char \****prefix***, void \****userdata***, char \*\*\****ret\_nodes***, sd\_bus\_error \****ret\_error***);**

**int sd\_bus\_add\_node\_enumerator(sd\_bus \****bus***, sd\_bus\_slot \*\****slot***, const char \****path***, sd\_bus\_node\_enumerator\_t** *callback***, void \****userdata***);**

## DESCRIPTION

**sd\_bus\_add\_node\_enumerator()** 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 **org.freedesktop.DBus.Introspectable.Introspect** or **org.freedesktop.DBus.ObjectManager.GetManagedObjects** are called on a D-Bus service managed by sd-bus).

*callback* is called with the path and userdata pointer registered with **sd\_bus\_add\_node\_enumerator()**. When called, it should store all the child object paths of the given path prefix in *ret\_nodes* 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 *ret\_error* 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 *ret\_error* take priority over negative return values.

Note that a node enumerator callback will only ever be called for a single path prefix and hence, for normal operation, *prefix* 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 [**sd\_bus\_add\_fallback\_vtable**(3)](/sd_bus_add_fallback_vtable/3.md).

When **sd\_bus\_add\_node\_enumerator()** succeeds, a slot is created internally. If the output parameter *slot* is **NULL**, a "floating" slot object is created, see [**sd\_bus\_slot\_set\_floating**(3)](/sd_bus_slot_set_floating/3.md). 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 [**sd\_bus\_slot\_unref**(3)](/sd_bus_slot_unref/3.md).

## RETURN VALUE

On success, **sd\_bus\_add\_node\_enumerator()** returns a non-negative integer. On failure, it returns a negative errno-style error code.

### Errors

Returned errors may indicate the following problems:

**-EINVAL**

One of the required parameters is **NULL** or *path* is not a valid object path.

**-ENOPKG**

The bus cannot be resolved.

**-ECHILD**

The bus was created in a different process, library or module instance.

**-ENOMEM**

Memory allocation failed.

## NOTES

Functions described here are available as a shared library, which can be compiled against and linked to with the **libsystemd** [**pkg-config**(1)](/pkg-config/1.md) 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)](/getenv/3.md), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not call [**setenv**(3)](/setenv/3.md) 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\_node\_enumerator\_t()** and **sd\_bus\_add\_node\_enumerator()** were added in version 221.

## SEE ALSO

[**sd-bus**(3)](/sd-bus/3.md), [**busctl**(1)](/busctl/1.md), [**sd\_bus\_add\_fallback\_vtable**(3)](/sd_bus_add_fallback_vtable/3.md), [**sd\_bus\_slot\_unref**(3)](/sd_bus_slot_unref/3.md)