---
name: "sd_bus_is_open"
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_is_open"
---

# sd\_bus\_is\_open(3)

Check whether the bus connection is open or ready

## NAME

sd\_bus\_is\_open, sd\_bus\_is\_ready - Check whether the bus connection is open or ready

## SYNOPSIS

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

**int sd\_bus\_is\_open(sd\_bus \****bus***);**

**int sd\_bus\_is\_ready(sd\_bus \****bus***);**

## DESCRIPTION

**sd\_bus\_is\_open()** checks whether the specified bus connection is open, i.e. in the process of being established, already established or in the process of being torn down. It returns zero when the connection has not been started yet (i.e. [**sd\_bus\_start**(3)](/sd_bus_start/3.md) or some equivalent call has not been invoked yet), or is fully terminated again (for example after [**sd\_bus\_close**(3)](/sd_bus_close/3.md)), it returns positive otherwise.

**sd\_bus\_is\_ready()** checks whether the specified connection is fully established, i.e. completed the connection and authentication phases of the protocol and received the **Hello()** method call response, and is not in the process of being torn down again. It returns zero outside of this state, and positive otherwise. Effectively, this function returns positive while regular messages can be sent or received on the connection.

The *bus* argument may be **NULL**, zero is also returned in that case.

To be notified when the connection is fully established, use [**sd\_bus\_set\_connected\_signal**(3)](/sd_bus_set_connected_signal/3.md) and install a match for the **Connected()** signal on the "org.freedesktop.DBus.Local" interface. To be notified when the connection is torn down again, install a match for the **Disconnected()** signal on the "org.freedesktop.DBus.Local" interface.

## RETURN VALUE

Those functions return 0 if the bus is *not* in the given state, and a positive integer when it is. On failure, a negative errno-style error code is returned.

### Errors

Returned errors may indicate the following problems:

**-ECHILD**

The bus connection has been created in a different process, library or module instance.

## 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\_is\_open()** was added in version 221.

**sd\_bus\_is\_ready()** was added in version 237.

## SEE ALSO

[**systemd**(1)](/systemd/1.md), [**sd-bus**(3)](/sd-bus/3.md), [**sd\_bus\_start**(3)](/sd_bus_start/3.md), [**sd\_bus\_close**(3)](/sd_bus_close/3.md), [**sd\_bus\_set\_connected\_signal**(3)](/sd_bus_set_connected_signal/3.md)