The HostOS extension is not all that useful in itself, rather, it is a building block other plugins and extensions can use to not repeat the same guesswork and logic.

The goal is to have a single place that remembers the host OS, whether set by the end-user in a Sketch, or via a macro, or some other way. This information can then be reused by other plugins.

See the Unicode extension for an example about how to use HostOS in practice.

Using the extension

The extension provides a HostOS singleton object.

#include <Kaleidoscope.h>
#include <Kaleidoscope-HostOS.h>

void someFunction(void) {
  if (HostOS.os() == kaleidoscope::hostos::LINUX) {
    // do something linux-y
  if (HostOS.os() == kaleidoscope::hostos::MACOS) {
    // do something macOS-y


void setup(void) {
  Kaleidoscope.setup ();

Extension methods

The extension provides the following methods on the HostOS singleton:


Returns the stored type of the Host OS.


Sets the type of the host OS, overriding any previous value. The type is then stored in EEPROM for persistence.

Host OS Values

The OS type (i.e. the return type of .os() and the arguments to .os(type)) will be one of the following:

  • kaleidoscope::hostos::LINUX

  • kaleidoscope::hostos::MACOS

  • kaleidoscope::hostos::WINDOWS

  • kaleidoscope::hostos::OTHER

For compability reasons, kaleidoscope::hostos::OSX is an alias to kaleidoscope::hostos::MACOS.

Focus commands

The plugin provides the FocusHostOSCommand object, which, when enabled, provides the hostos.type Focus command.

hostos.type [type]

Without argument, returns the current OS type set (a numeric value).

With an argument, it sets the OS type.

This command can be used from the host to reliably set the OS type within the firmware.


Further reading

Starting from the example is the recommended way of getting started with the extension.