---
name: "sd_bus_get_current_handler"
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_get_current_handler"
---

# sd\_bus\_get\_current\_handler(3)

Query information of the callback a bus object is currently running

## NAME

sd\_bus\_get\_current\_handler, sd\_bus\_get\_current\_message, sd\_bus\_get\_current\_slot, sd\_bus\_get\_current\_userdata - Query information of the callback a bus object is currently running

## SYNOPSIS

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

**typedef int (\*sd\_bus\_message\_handler\_t)(sd\_bus\_message \****m***, void \****userdata***, sd\_bus\_error \****ret\_error***);**

**sd\_bus\_message\_handler\_t sd\_bus\_get\_current\_handler(sd\_bus \****bus***);**

**sd\_bus\_message\* sd\_bus\_get\_current\_message(sd\_bus \****bus***);**

**sd\_bus\_slot\* sd\_bus\_get\_current\_slot(sd\_bus \****bus***);**

**void\* sd\_bus\_get\_current\_userdata(sd\_bus \****bus***);**

## DESCRIPTION

Whenever sd-bus is about to invoke a user-supplied callback function, it stores the current callback, D-Bus message, slot and userdata pointer and allows these to be queried via **sd\_bus\_get\_current\_handler()**, **sd\_bus\_get\_current\_message()**, **sd\_bus\_get\_current\_slot()** and **sd\_bus\_get\_current\_userdata()**, respectively. If *bus* cannot be resolved or if execution does not reside in a user-supplied callback of *bus*, these functions return **NULL**.

## RETURN VALUE

On success, these functions return the requested object. On failure, they return **NULL**.

## 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\_get\_current\_handler()**, **sd\_bus\_get\_current\_message()**, **sd\_bus\_get\_current\_slot()**, and **sd\_bus\_get\_current\_userdata()** were added in version 221.

## SEE ALSO

[**systemd**(1)](/systemd/1.md), [**sd-bus**(3)](/sd-bus/3.md)