Detect MS Windows

Question

Challenge

Create a program that returns a truthy value when run on Microsoft Windows (for simplicity we'll stick with Windows 7, 8.1 and 10) and a falsey value when run on any other operating system (OSX, FreeBSD, Linux).

Rules

• Code that fails to run/compile on a platform doesn't count as a falsey value.

Winning criteria

I'm labelling this as code-golf, so lowest score wins, but I'm also very interested in seeing creative solutions to this problem.

Answer 1

Vim, 2 bytes

<C-a>1

On Windows, <C-a> (ctrl+a) is mapped by default to Select All. If you type a 1 in select mode in Windows, it replaces the selection with what you typed (1) leaving a 1 in the buffer.

On other operating systems, <C-a> by default is mapped to Increment number. Because there's no number to increment, it's a no-op, and then the 1 increases the count but in terms of the buffer is a no-op.

1 is truthy in Vim, and an empty string is falsy

Answer 2

MATLAB, 4 bytes

ispc

From the documentation:

tf = ispc returns logical 1 (true) if the version of MATLAB® software is for the Microsoft® Windows® platform. Otherwise, it returns logical 0 (false).

There are also the functions ismac and isunix. I'll leave it to the reader to figure out what those functions do. Mego kindly asked for diagrams explaining ismac and isunix so I've tried to illustrate it here:

It was not asked for a diagram of ispc but I can reveal that the behaviour is pretty similar, except substitute OSX and Unix with Windows.

---

Second approach:

Here's a second approach with getenv using 23 bytes that should be bullet proof, unless there's another operating system starting with W:

x=getenv('OS');x(1)==87

getenv 'name' searches the underlying operating system environment list for text of the form name=value, where name is the input character vector. If found, MATLAB® returns the character vector value. If the specified name cannot be found, an empty matrix is returned.

Answer 3

Python 2.7.10, 24 bytes

import os
0/('['>os.sep)

Thanks to FlipTack for 3 bytes

This program takes advantage of the fact that Windows is the only OS to use \ as a path separator. Normally this is frustrating and bad, but for once it is actually an advantage. On Windows, '['>os.sep is false, and thus 0/0 is computed, causing a ZeroDivisionError and exiting with a non-zero exit code. On non-Windows platforms, '['>os.sep is true, making the expression 0/1, which does nothing, and the program exits with exit code 0.

Answer 4

x86 Assembly, 7 bytes (Inspired by Runemoro's answer)

31 DB 89 D8 40 CD 80

Or

xor ebx, ebx 
mov eax, ebx
inc eax
int 0x80

Description

First of all, we'll set eax to 1 (the system call number for exit(int val) for Linux, FreeBSD and OSX). Then, we'll call the interrupt gate 0x80 which is the system call gate for Linux, FreeBSD and OSX. That would cause the program to exit with status of ebx which is 0 (false).

On Windows int 0x80 is an invalid gate (It uses 2e as a syscall gate) and would crash the program, causing it to end with a positive exit code (true).

Edit: Would not work on OSX since it has a different argument-passing convention on 32 bit (by the stack).

References and further reading

• FreeBSD - System Calls: Information about system calls in FreeBSD.
• System calls in the Linux kernel. Part 2.: A great article about Linux's system calls.
• Linux Syscall Reference: a system call numbers reference for Linux.
• Windows Syscall Shellcode : An article about directly calling system calls in windows from assembly.
• Making system calls from Assembly in Mac OS X: An article about system calls on OSX.

Answer 5

C, 44 43 38 36 bytes

Thanks to @Downgoat for a byte! ^{crossed out 44 is still regular 44}
Thanks to @Neil for two bytes!

f(){return
#ifdef WIN32
!
#endif
0;}

Answer 6

PHP, 22 bytes

`<?=PATH_SEPARATOR>":";`  

prints 1 if the path separator is semicolon (colon or empty for all other OSs except for DOS and OS/2), else nothing.

also 22 bytes, but not that safe:

<?=strpos(__FILE__,92);

prints a positive integer if the file path contains a backslash; else nothing.
A safe alternative with 27 bytes: <?=DIRECTORY_SEPARATOR>"/"; prints 1 or nothing.

A strange find: <?=__FILE__[1]==":"; (20 bytes) should be, not safe either, but ok. But although __FILE__ pretends to be a string (I tried var_dump and gettype), indexing it throws an error, unless you copy it somewhere else (concatenation also works) or use it as a function parameter.

Edit:
<?=(__FILE__)[1]==":"; (also 22 bytes) works in PHP 7; but that´s because the parentheses copy the constant´s value to a temporary variable.

27 bytes: <?=stripos(PHP_OS,win)===0;
tests if predefined PHP_OS constant starts with win (case insensitive; Windows,WIN32,WINNT, but not CYGWIN or Darwin); prints 1 for Windows, else nothing.

17/18 bytes:

<?=strlen("
")-1;

prints 1 if it was stored with Windows linebreak (also on DOS, OS/2 and Atari TOS - although I doubt that anyone ever compiled PHP for TOS), else 0.

You could also check the constant PHP_EOL.

more options:

PHP_SHLIB_SUFFIX is dll on Windows, but not necessarily only there.
php_uname() returns info on the operating system and more; starts with Windows for Windows.
$_SERVER['HTTP_USER_AGENT'] will contain Windows when called in a browser on Windows.
<?=defined(PHP_WINDOWS_VERSION_BUILD); (38 bytes) works in PHP>=5.3

conclusion

The only failsafe way to tell if it´s really Windows, not anything looking like it, seems to be a check on the OS name. For PHP: php_os() may be disabled for security reasons; but PHP_OS will probably always contain the desired info.

Answer 7

Befunge-98, 7 bytes

6y2%!.@

Try it online!

This works by querying the system path separator, which is \ on Windows and / on other operating systems.

6y            System information query: #6 returns the path separator.
  2%          Test the low bit - this will be 1 for '/' and 0 for '\'.
    !         Not the value, so it becomes 0 for '/' and 1 for '\'.   
     .@       Output the result and exit.

Answer 8

Mathematica, 28 bytes

$OperatingSystem=="Windows"&

Answer 9

Java 8, 33 bytes

Special thanks to Olivier Grégoire for suggesting separatorChar, and Kritixi Lithos for -1 byte!

This is a lambda expression which returns a boolean. This can be assigned to Supplier<Boolean> f = ...; and called with f.get().

()->java.io.File.separatorChar>90

Try it online! - the server isn't windows, so this prints false. However, in my windows machine, the same code prints true.

What this code does is get the System's file seperator, and check whether its codepoint is larger than the character [. This true for Windows, as it uses \ as the seperator - but every other OS uses /, which has a lower code in the ASCII table.

Answer 10

J, 7 bytes

6=9!:12

This is a verb (similar to a function) that uses the builtin foreign conjunction 9!:12 to acquire the system type where 5 is Unix and 6 is Windows32.

Answer 11

R, 15 bytes

.Platform$O>"v"

Thanks to plannapus for the suggestion to use partial matching for list element extraction.

.Platform is a list with some details of the platform under which R was built. There is an element OS.type (the only element with name starting with "O") which is character string, giving the Operating System (family) of the computer. One of "unix" or "windows".

So "unix" is less then "v", but "windows" is greater then "v". Other valid 15 bytes answers are

.Platform$O>"V"
.Platform$O>"w"
.Platform$O>"W"

R is being developed for the Unix-like, Windows and Mac families of operating systems. Other OS families are not supported.

Answer 12

Perl, 11 bytes

print$^O=~MS

^O should be replaced by a literal Control-O.

Outputs 1 on windows, nothing on another OS.

Note that I'm not using say as it adds a trailing newline, which is truthy in Perl.

-2 bytes thanks to primo. (and fixed potential issues)
-1 bytes thanks to ais523.

Answer 13

julia, 10 bytes

is_windows

A function that returns true for windows

Answer 14

x86 machine code, 9 bytes

40 39 04 24 75 02 CD 80 C3

Compiled from:

inc eax        ; set eax to 1
cmp [esp], eax ; check if [esp] == 1 (linux)
jne windows    ; jump over "int 0x80" if on windows
int 0x80       ; exit with exit code 0 (ebx)
windows:
ret            ; exit with exit code 1 (eax)

Answer 15

JavaScript, 42 30 26 25 bytes

console.log((
//Begin
_=>navigator.oscpu[0]>'V'
//End
)())

Tested with Firefox. (Chrome doesn't have the oscpu property.) Since lowercase letters have a higher character code than uppercase letters, this depends on the first letter of navigator.oscpu being uppercase and not being W, X, Y or Z on any platform that Firefox supports (other than Windows, of course). According to this post, that is the case.

Edits

1. Saved 12 bytes thanks to Neil.
2. Saved another four bytes
3. Saved another byte thanks to Blender.

Answer 16

C#, 61 48 bytes

()=>(int)System.Environment.OSVersion.Platform<4

Saved 13 bytes thanks to TheLethalCoder

Or a full program at 83 bytes:

class P{static int Main(){return(int)System.Environment.OSVersion.Platform<4?1:0;}}

Various Windows variants use enum values 0 to 3 in the Microsoft .NET implementation. 4 is Unix, 5 is Xbox [360] (which I won't consider "Windows"), 6 is MacOSX. Mono uses the same values, adding 128 for Unix/Linux in earlier versions.

Therefore, anything < 4 is Windows, and everything else is not Windows.

Answer 17

Batch, 50 bytes

@if %OS%==Windows_NT if not exist Z:\bin\sh echo 1

Edit: Fixed to ignore DOS instead of claiming that it's Windows.

The only other way I know of running Batch outside of Windows is to use WINE which by default will map Z: to /. Therefore if Z:\bin\sh exists, chances are that it's /bin/sh, so not MS Windows.

I don't know what WINE sets %OS% to, but if it's not Windows_NT then I could save 23 bytes.

Answer 18

Node.js, 27 16 15 13 bytes

Thanks to @Patrick, who shaved 12 bytes off my solution using Node's REPL:

_=>os.EOL>`
`

Original solution:

_=>require('path').sep!='/'

Answer 19

Excel VBA, 41 40 30 29 26 24 Bytes

Immediate windows function that returns true if the system's OS code starts is longer than length 3, because the info is restricted to output either else mac or pcdos this returns true only on windows pcs

?[Len(Info("SYSTEM"))>3]

Previous Versions

''# Ignore the second `"` that follows every `\` - its only there for highlighting 

?Left(Environ("OS"),1)="W"                 # 24 Bytes

?InStr(ThisWorkbook.Path,"\"")             # 29 Bytes

?Mid(ThisWorkbook.Path,3,1)="\""           # 30 Bytes, Restricted to local Files

?Application.PathSeparator="\""            # 30 Bytes

?Left(Application.OperatingSystem,1)="W"   # 40 Bytes

Changes

-1 Thanks to Neil for using Left(...,1) over Mid(...,1,1)

-10 Thanks to ChrisH for pointing out @Mego's Path Separator Trick

-1 For Checking the WorkbookPath for "\" rather than using Application.Path Separator

-4 For switching to Environ()

-2 For switching to [Len(Info(...

Novel Solution, 51 bytes

Novel subroutine that outputs, to the VBE immediates window, a 1 (truthy) under windows and 0 (falsey) under mac by method of conditional compilation.

Sub a
i=1
#If Mac Then
i=0
#End If
Debug.?i
End Sub

Answer 20

QBasic, 31 bytes

?INSTR(ENVIRON$("COMSPEC"),"W")

Prints non-zero under Windows, 0 under everything else.

COMSPEC is an environment variable unique to Microsoft OSs. It points to the command interpreter, typically command.com or cmd.exe. Under Windows, the command interpreter sits somewhere in the Windows directory; under MS-DOS, it sits in the DOS directory or on the root of the disk, and under any other OS, it doesn't exist.

By checking to see if the value of COMSPEC contains a "W", we can tell the difference between Windows and not-Windows.

Answer 21

Perl 6,  19  18 bytes

put $*DISTRO.is-win

put ?($*CWD~~/\\/)

Both output True␤ or False␤ depending on the system it is run on.

Answer 22

APL (Dyalog), 21 bytes

'W'∊∊#⎕WG'APLVersion'

Try it online!

#⎕WG'APLVersion' Root (#) Window Get property APL&hairsp;Version

∊ enlist (flatten)

'W'∊ is W a member? (no non-Windows return values contain a capital W)

Answer 23

Haskell, 39 31 bytes

import System.Info
f=os!!0=='m'

I check for the first letter output of "m", which should be "mingw" for windows. As far as I could tell, there is no other OS which starts with M. The information comes from https://github.com/ghc/ghc/blob/master/compiler/utils/Platform.hs

Answer 24

tcl, 38 bytes

 expr [lsearch $tcl_platform windows]>0

Answer 25

PHP 17 Bytes

The following will output 1 if windows and nothing if anything else. Ignoring notices of string convertion.

<?=PHP_OS==WINNT;

Try online Online tests for linux because the sandbox is linux for PoC.

Answer 26

8th, 11 bytes

 
os 1- not .
 

Prints true on Windows, false on Linux and macOS. Other platforms supported by 8th are Android, iOS and Raspberry Pi, but I am not able to test on them.

Ungolfed version (with comments)

 
G:os  \ Return a number n indicating the operating system 
      \ 0 for Linux
      \ 1 for Windows 
      \ 2 for macOS
      \ 3 for Android 
      \ 4 for iOS 
      \ 5 for Raspberry Pi
n:1-  \ Subtract 1
G:not \ If Windows --> true, otherwise --> false
.     \ Print result
 

Answer 27

Java 8, 49 bytes

()->System.getenv().get("OS").contains("Windows")

Longer than the other Java answer, but takes a different approach.

This lambda fits in a Supplier<Boolean> and can be tested with the following program:

public class DetectMSWindows {

  public static void main(String[] args) {
    System.out.println(f(() -> System.getenv().get("OS").contains("Windows")));
  }

  private static boolean f(java.util.function.Supplier<Boolean> s) {
    return s.get();
  }

}

Answer 28

bash + coreutils, 5 bytes

rm $0

Also works in most other POSIXy shells. (Note that Windows ports of bash and rm exist; even though they're only normally used with more heavily POSIXy operating systems, this isn't an entirely vacuous entry.) Outputs via exit code (0 = false, 1 = true). Can be counted as 4 bytes if you're allowed to assume a filename (e.g. rm a). Note that this can potentially fail in the case of very weird filenames (which rm will interpret as arguments due to the lack of quoting, and possibly delete files you care about, so I'd advise against running this program from a file with a weird name).

Note: deletes the program from disk as a side effect, or at least tries to. In the case where we're running on Windows, the OS will fail to delete the running file (an operation that Windows disallows either by default or full stop), and thus rm will error out. bash catches the error and converts it into an exit code (thus the program as a whole terminates normally). Most of the other entries here are using 0 for falsey and 1 for truthy in exit codes, so this does the same; note that bash's if statement doesn't accept integers at all (rather, it accepts commands and branches based on whether they run successfully, and arithmetic tests are done via the means of programs like test that intentionally report a "crash" on a failed comparison), so this is on shakier ground in terms of legality than programs that output via exit code in languages where 0 is valid in an if statement test and sends the program to the else branch.

Answer 29

Python 3 (13 bytes)

import winreg

Returns with exit code zero (generally true in shells) if on windows, and with a non-zero exit code otherwise.

If you prefer it the other way round, there is a 12 bytes solution: import posix.

Answer 30

TrumpScript, 17 bytes

America is great.

Try it online!

---

This program, if run on windows, will print:

The big problem this country has is being PC

This is considered a truthy value.

---

Empty output and the following value are falsy:

Boycott all Apple products  until such time as Apple gives cellphone info to authorities regarding radical Islamic terrorist couple from Cal

The empty output will occur on any linux system (for this program), the long apple response obviously occurs on Mac (for any program). On TIO, the backend (I'm assuming) is a Unix operating system, so you can only get the falsy value; on my computer I get the PC message.

---

Not 100% sure if this counts as an error message (which would invalidate the answer), but if you didn't know about this it was probably worth a laugh for you.

Answer 31

FPC, 61 chars

begin{$ifdef win32}write('f');{$else}write('nf');{$endif}end;

Answer 32

LibreOffice Calc / OpenOffice Calc, 21 bytes

Code:

=INFO("system")="WNT"

Microsoft Excel, 23 bytes

Code:

=INFO("system")="pcdos"

Result:

Returns TRUE if Windows; FALSE otherwise.

Answer 33

tcl, 51

puts [string match windows $tcl_platform(platform)]

I don't have a Windows machine online, but on http://rextester.com/live/OVTY1488 replace windows by unix to see it output 1 instead of 0.

2nd attempt:

tcl, 40

puts [string match W* $tcl_platform(os)]

assuming Windows is the only system the name begins on a W.

3rd attempt:

tcl, 26

puts [info exists env(OS)]

assuming Windows is the only system the OS environment variable is defined.

Answer 34

IBM/Lotus Notes Formula Language, 22 21 bytes

@Like(@Platform;"W%")

Previous versions:

@Left(@Platform;1)="W"

or

@Begins(@Platform;"W")

Computed field formula on a Notes form. @Platform returns 1 of:

AIX/64
Linux/64
Macintosh
OS/400®
UNIX
Windows/32
Windows/64

So the formula returns 1 (@True) if the platform starts with "W" and 0 (@False) if not.

Answer 35

Ruby, 38 bytes

Stealing the code from here:

exit (RUBY_PLATFORM=~/(?<!r)win/)!=nil

Return 0 on OK, to keep with shell conventions. We need the funny (?<!r) negative look-behind to avoid matching darwin, although if Microsoft device to make a vrwin Windows version for virtual reality the code will fail... On JRuby, though, this doesn't work so well, so instead:

Ruby including JRuby, 52 bytes

exit (RbConfig::CONFIG['host_os']=~/(?<!r)win/)!=nil

I don't have raw Windows, just Cygwin, but if the host_os is windows then we need to distinguish nil and 0.

Ruby plus gem install os, 25 (+9?)

This needs an extra gem, so we might have to add an extra 9 bytes for gem i os at the command line:

require 'os'
exit OS.windows?

This also avoids the darwin problem completely!

Answer 36

PHP, 18 bytes

<?=!(PHP_EOL^'=');

Explanation

PHP_EOL, as its name might suggest, returns the line separator on a given system. On Windows, this is CRLF, and on other platforms, this is LF.

^ is binary XOR. '=' XOR "\r" is '0', and PHP's string bitwise operations truncate to the length of the shortest string, so "\r\n" XOR '=' is also '0'.

! is boolean NOT. In PHP, "0" is considered falsy. So, when we're on Windows, PHP will negate this to true. When we're not on Windows, we get a truthy value ('7') which PHP negates to false.

<?= is the short opening tag for echo.

Answer 37

Ruby 2, 17 14 bytes

17 byte solution: Gem.win_platform? This only works on the newer versions of ruby, as in the older versions you would have to require rubygems.

---

14 byte solution:

system 'del a' This command outputs true if on windows, because there is a command called del in Windows, but outputs nil (falsey) on Linux and Mac because there is no such command as del in Unix. Oh, and if you are on windows it will delete a file called a in your current directory, that's an unintended side effect :P

Answer 38

Powershell 6, 10 bytes

$isWindows

Powershell 6 intoduce 3 predefined variables: $isWindows, $isLinux and $IsMacOs.

Answer 39

Elixir, 19 bytes

{:win32,_}=:os.type

Exit code 0 for Windows, 1 for others.

Answer 40

Scala, 71 bytes

object W extends App{print(sys.env.get("OS").get.contains("Windows"))}

Answer 41

Lua, 21 Bytes

os.execute"dir c:\\"

It will error if not on windows and list the C:\ directory if on windows.

Answer 42

Dartlang, 43 bytes

import'dart:io';main()=>Platform.isWindows;

First answer one here, so I hope this is okay :)

Answer 43

D, 43 bytes

int f(){version(Windows)return 0;return 1;}

D ... is horrible at golfing. But it does have a version construct, so I thought I'd post an answer in D.

And ... there's really no point in putting a TIO link, since TIO is ran on only one type of OS.

Answer 44

SQL 2017, 61 bytes

SELECT IIF(host_platform='Linux',0,1)FROM sys.dm_os_host_info

SQL 2017 is the first MS SQL version that can run on a platform other than Windows. The system view sys.dm_os_host_info returns either Linux or Windows, so (at least in this version) anything that isn't on Linux is on Windows.

Answer 45

Python 3, 29 bytes

import os;exit(os.name!='nt')

Probably should have tryed that first....

Previous answer (41 bytes)

Two answers I found that are the same size

import os;exit(-hasattr(os,"P_DETACH")+1)

and

import sys;exit(-hasattr(sys,"winver")+1)

also -+1 is a neat way to negate the output, gonna keep that one noted

Answer 46

Racket, 26 17 bytes

Shameless plug for the TCL answer I saw that used the OS environment variable.

(and(getenv"OS"))

---

(Old answer)

Pretty straight forward. system-type with no argument returns a symbol indicating the system operating system type.

(eq?'windows(system-type))

Answer 47

Nim, 37 bytes

quit when defined(windows): 0 else: 1

Returns exit code 0 for Windows, 1 for all other operating systems. Uses conditional compilation with when.

Answer 48

PowerShell, 17

gdr|? P* -like *y

Abusing the fact that there's no Registry PSProvider on non-Windows systems.

Answer 49

Node.js, 23 bytes

_=>os.platform=="win32"

Answer 50

Rust, 14 bytes

||!cfg!(unix);

The target_family attribute is windows on Windows and (most) others have unix.