---
name: "rtapi_is"
section: "3rtapi"
platform: "linux"
package: "linuxcnc-uspace-dev"
version: "1:2.9.4-2+deb13u1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/rtapi_is"
---

# rtapi\_is(3rtapi)

details of rtapi configuration

## NAME

rtapi\_is - details of rtapi configuration

## SYNTAX

int rtapi\_is\_kernelspace()

int rtapi\_is\_realtime()

## DESCRIPTION

**rtapi\_is\_kernelspace()** returns nonzero when rtapi modules run in kernel space (e.g., under RTAI) and zero when they run in userspace (e.g., under uspace).

**rtapi\_is\_realtime()** returns nonzero when capable of running with realtime guarantees.  For rtai, this always returns nonzero (but actually loading realtime modules will fail if not running under the appropriate kernel).  For uspace, this returns nonzero when the running kernel indicates it is capable of realtime performance.  If **rtapi\_app** is not setuid root, this returns nonzero even though **rtapi\_app** will not be able to obtain realtime scheduling or hardware access, so e.g., attempting to **loadrt** a hardware driver will fail.

## REALTIME CONSIDERATIONS

May be called from non-realtime or from realtime setup code. **rtapi\_is\_realtime()** may perform filesystem I/O.

## RETURN VALUE

Zero for false, nonzero for true.