# CMAKE_SYSTEM_NAME

The name of the operating system for which CMake is to build. See the `CMAKE_SYSTEM_VERSION` variable for the OS version.

Note that `CMAKE_SYSTEM_NAME` is not set to anything by default when running in script mode, since it's not building anything.

## System Name for Host Builds

`CMAKE_SYSTEM_NAME` is by default set to the same value as the `CMAKE_HOST_SYSTEM_NAME` variable so that the build targets the host system.

## System Name for Cross Compiling

`CMAKE_SYSTEM_NAME` may be set explicitly when first configuring a new build tree in order to enable cross compiling. In this case the `CMAKE_SYSTEM_VERSION` variable must also be set explicitly.

## System Names Known to CMake

The following is a list of possible values, each associated with corresponding operating systems or environments.

Value | Name
--- | ---
`ADSP` | Analog Devices Audio Digital Signal Processing
`AIX` | IBM Unix operating system
`Android` | Android operating system
`ARTOS` | Operating system for microcontrollers
`BeOS` | Operating system for personal computers (discontinued)
`BlueGeneL` | Blue Gene/L static environment
`BlueGeneP-dynamic` | Blue Gene/P dynamic environment
`BlueGeneP-static` | Blue Gene/P static environment
`BlueGeneQ-dynamic` | Blue Gene/Q dynamic environment
`BlueGeneQ-static` | Blue Gene/Q static environment
`BSDOS` | BSD operating system (discontinued)
`Catamount` | Operating system for Cray XT series
`CrayLinuxEnvironment` | Cray Linux Environment
`CYGWIN` | Cygwin environment for Windows
`Darwin` | Apple stationary operating systems (macOS, OS X, etc.)
`DOS` | MS-DOS or compatible
`DragonFly` | BSD-derived operating system
`eCos` | Real-time embedded operating system
`Emscripten` | Compiler toolchain to WebAssembly
`Euros` | Real-time operating system for embedded devices
`FreeBSD` | FreeBSD operating system
`Fuchsia` | Operating system by Google based on the Zircon kernel
`Generic-ADSP` | Generic ADSP (Audio DSP) environment
`Generic-ELF` | Generic ELF (Executable and Linkable Format) environment
`Generic` | Some platforms, e.g. bare metal embedded devices
`GHS-MULTI` | Green Hills Software MULTI environment
`GNU` | GNU/Hurd-based operating system
`Haiku` | Unix operating system inspired by BeOS
`HP-UX` | Hewlett Packard Unix
`iOS` | Apple mobile phone operating system
`Linux` | All Linux-based distributions
`Midipix` | POSIX-compatible layer for Windows
`MirBSD` | MirOS BSD operating system
`MP-RAS` | MP-RAS UNIX operating system
`MSYS` | MSYS environment (MSYSTEM=MSYS)
`NetBSD` | NetBSD operating systems
`OpenBSD` | OpenBSD operating systems
`OpenVMS` | OpenVMS operating system by HP
`OS2` | OS/2 operating system
`OSF1` | Compaq Tru64 UNIX (formerly DEC OSF/1, Digital Unix) (discontinued)
`QNX` | Unix-like operating system by BlackBerry
`RISCos` | RISC OS operating system
`SCO_SV` | SCO OpenServer 5
`SerenityOS` | Unix-like operating system
`SINIX` | SINIX operating system
`SunOS` | Oracle Solaris and all illumos operating systems
`syllable` | Syllable operating system
`Tru64` | Compaq Tru64 UNIX (formerly DEC OSF/1) operating system
`tvOS` | Apple TV operating system
`ULTRIX` | Unix operating system (discontinued)
`UNIX_SV` | SCO UnixWare (pre release 7)
`UnixWare` | SCO UnixWare 7
`visionOS` | Apple mixed reality operating system
`WASI` | WebAssembly System Interface
`watchOS` | Apple watch operating system
`Windows` | Windows stationary operating systems
`WindowsCE` | Windows Embedded Compact
`WindowsPhone` | Windows mobile phone operating system
`WindowsStore` | Universal Windows Platform applications
`Xenix` | SCO Xenix Unix operating system (discontinued)

Platform-specific notes:

- MSYS2's `msys/cmake` package (`/usr/bin/cmake`) works only under `MSYSTEM=MSYS` environments, with system name `MSYS`. Under other environments like `MSYSTEM=MINGW64`, use another package such as `mingw64/mingw-w64-x86_64-cmake` (`/mingw64/bin/cmake`), which targets `MSYSTEM=MINGW64` with system name `Windows`.

- Cygwin's `cmake` package (`/usr/bin/cmake`) uses system name `CYGWIN`. A non-cygwin CMake on Windows (e.g. `$PROGRAMFILES/CMake/bin/cmake`) uses system name `Windows` even when it runs under a Cygwin environment.

## Removed Platforms

The following platforms were once supported by CMake and got removed either due to platform's EOL, or other incompatibilities:

Value | Name | Removed in CMake
--- | --- | ---
`kFreeBSD` | FreeBSD kernel with a GNU userland | 4.1