Shut down the computer!

Question

Challenge:

In the programming language of your choice, shut down the machine that your code was executed on.

Rules

• No shutting down by resource exhaustion (e.g.: forkbomb to force shutdown)
• You are allowed to write code that only works in a specific environment/OS, if you wish.
• Standard loopholes are forbidden

---

This is code-golf, thus the lowest amount of bytes wins!

Answer 1

Assembly (x86/x64, Linux, as), 22 21 19 bytes

mov  $0x58,       %al  # 2 bytes: b0 58
mov  $0xfee1dead, %ebx # 5 bytes: bb ad de e1 fe
mov  $0x28121969, %ecx # 5 bytes: b9 69 19 12 28
mov  $0x4321fedc, %edx # 5 bytes: ba dc fe 21 43
int  $0x80             # 2 bytes: cd 80

Must be run as root.

This is equivalent to pressing the power button and not a safe way to power off your PC. Make sure you close all open applications and execute sync to flush all file system buffers before executing this program, to at least minimize the risk of file corruption.

Test run

$ as -o poweroff.o poweroff.s
$ ld -o poweroff   poweroff.o
ld: warning: cannot find entry symbol _start; defaulting to 0000000000400078
$ sudo sh -c 'sync && ./poweroff'
root's password:

Followed by darkness.

How it works

int $0x80 invokes a software interrupt. It works on both x86 and x64, but has been deprecated for over a decade now and should not be used in production code. x64 code should use syscall instead. x86 should use sysenter, but it is too cumbersome for code golf.

The resulting action from the syscall depends on registers EAX - EDX, ESI, and EDI. The Linux Syscall Reference shows all syscalls that are available via int $0x80.

When EAX holds 0x58 (88), reboot is called, which can also be used to power off, put to sleep, or hibernate the computer, as well as switching kernels and disabling or enabling the Ctrl - Alt - Del key combo.

At the start of the program – and by compiling with as or gcc -nostdlib, we can make sure that we're actually at the start of the program – most registers are set to 0. This includes EAX, so we can use mov $0x58, %al to set the lower 8 bits of EAX to 0x58, thus setting EAX itself to 0x58. This saves two bytes over manually zeroing the register with xor %eax, %eax and one more over the straighforward mov $0x58, %eax which encodes 0x58 in 32 bits.

The first two arguments to reboot are magic numbers, presumably to prevent accidental reboots, and are read from registers EBX and ECX. Unless these numbers are equal to certain constants, reboot refuses to perform any action.

• The first magic number must equal 0xfee1dead (feel dead), probably referring to the power off / death of the PC.

• The second magic number can be equal to four different constants, although the latter three did not work in ancient versions of Linux. All of them seem to refer to the subsequent power on / birth of the PC.

  • 0x28121969 represents Linus Torvalds's birthday (December 28, 1969).

  • 0x05121996 represents Patricia Torvalds's birthday (December 5, 1996).

  • 0x16041998 represents Daniela Torvalds's birthday (April 16, 1998).

  • 0x20112000 represents Celeste Torvalds's birthday (November 20, 2000).

  Patricia, Daniela, and Celeste Torvalds are Linus Torvalds's three daughters.

• The EDX register selects the type of "reboot" we want. 0x4321fedc is RB_POWER_OFF, shutting the PC down and powering it off.

• Finally, the value of the ESI register is ignored for RB_POWER_OFF; the value of the EDI register is ignored entirely by reboot.

Alternate version, x64-only, 19 bytes

On x64, we can use a proper syscall for the same byte count.

mov     $0xa9,       %al  # 2 bytes: b0 a9
mov     $0xfee1dead, %edi # 5 bytes: bf ad de e1 fe
mov     $0x28121969, %esi # 5 bytes: be 69 19 12 28
mov     $0x4321fedc, %edx # 5 bytes: ba dc fe 21 43
syscall                   # 2 bytes: 0f 05

The only differences lie in the instruction (syscall vs int $0x80), the value of __NR_REBOOT (0xa9 vs 0x58), and the involved registers.

Answer 2

PowerShell, 13 bytes

Stop-Computer

Pretty self-explanatory? Doesn't work on PowerShell core, so it won't work on PowerShell for Linux/MacOS (already tried it on TIO :-D ).

Bonus Garbage Submission, 12 bytes

gcm s*r|iex

In my testing, this works on Windows 2003 with PowerShell 2.0. It won't work on most of the newer versions, and it may not work depending on which modules are installed. It's quite terrible!

This searches the list of commands for any with the pattern s*r and then runs all of them! To be clear, this is dangerous, don't do this!

The trick of course, is getting a list of commands that don't have any mandatory parameters, otherwise PowerShell will prompt for a value.

On my 2003 machine, the 3 commands it returns are:

CommandType     Name                                                Definition                                         
-----------     ----                                                ----------                                         
Application     scrnsave.scr                                        C:\WINDOWS\system32\scrnsave.scr                   
Application     ssmarque.scr                                        C:\WINDOWS\system32\ssmarque.scr                   
Cmdlet          Stop-Computer                                       Stop-Computer [[-ComputerName] <String[]>] [[-Cr...

Yes, it does launch the marquee screensaver, but no, it does not wait for it to complete before launching Stop-Computer.

This approach can work on newer machines, again depending on which modules are installed, but the best I could do on Windows 2012 and 2016 was 14 bytes:

gcm sto*er|iex

(and yeah, sure, the winbatch submission will work in PowerShell and it's shorter, but.. that's no fun)

Answer 3

Batch, 10 bytes

On windows, this would suffice

shutdown/s

This will set up a shutdown in one minute.

Alternatively, as @flashbang points out:

shutdown/p

This shuts down the computer immediately.

Answer 4

x86 machine code, Lenovo Z510, DOS COM or Bootloader, 7 bytes

BITS 16

mov ax, (1 << 13) | (7 << 10)
mov dx, 1804h
out dx, ax

Assembled into B8 00 3C BA 04 18 EF

I'm exploiting "You are allowed to write code that only works in a specific environment/OS, if you wish" to the ultimate level: this will only work on Lenovo Z510¹.

This writes SLP_TYPa << 10 | SLP_EN to the PM1a_CNT ACPI register, I dumped this values from the ACPI tables months ago for an answer about shutdown (where I give a bit of context to the code above).

This can be run either under DOS as a COM (just write the binary data into a file and change extension to "com") or as a bootloader.
For the latter write the standard signature and beware of the issues with modern firmware.

---

¹ Not strictly true, any system that happens to have the same ACPI configuration will also shutdown.

Answer 5

GRUB shell, 4 bytes

Golfed

halt

Command: halt --no-apm

The command halts the computer. If the --no-apm option is specified, no APM BIOS call is performed. Otherwise, the computer is shut down using APM.

Bonus

Here is a proof that GRUB shell is indeed Turning-complete (see comments):

Answer 6

65C02 machine code, 1 byte

STP instruction (0xDB):

STP stops the clock input of the 65C02, effectively shutting down the 65C02 until a hardware reset occurs (i.e. the RES pin goes low). This puts the 65C02 into a low power state. This is useful for applications (circuits) that require low power consumption, but STP is rarely seen otherwise.

(Source: http://www.6502.org/tutorials/65c02opcodes.html)

xxd dump:

00000000: db                                       .

Answer 7

Matlab, 21 Bytes

system('shutdown -s')

I haven't tried this (closing all programs to do a restart in the middle of the day isn't really tempting), but it should work.. This works...

I'll add a short explanation later, my laptop is currently off.

Answer 8

MATLAB, 11 bytes

!shutdown/p

Somewhat similar to Stewie Griffin's approach. However, MATLAB has way shorter ways of invoking system commands; in this case, ! is used. Windows does not need .exe for command names, so that's left out as well. The / option is still supported (I'm running Windows 10), and negates the need for the space. Alternatives are:

system shutdown/p % 17 bytes; uses so-called 'command' syntax.
dos shutdown/p    % 14 bytes; the 'dos' command can be used just as well.

Answer 9

SmileBASIC, 14 11 6 bytes

OPTION

Triggers a crash causing the 3DS to restart. I hope this counts.

Works in the most recent version.

Answer 10

Bash, 7 6 bytes

init 0

Assuming that the program is run as root.

Answer 11

Python 2, 29 bytes

import os;os.system('init 0')

Works on Linux systems and needs root privileges.

For Windows, 33 bytes

import os;os.system('shutdown/p')

Answer 12

Java, 101 98 62 42 bytes

()->{Runtime.getRuntime().exec("init 0");}

As @Snowman pointed out, the question didn't specify if a full program was needed, so this should still be acceptable.

Answer 13

Commodore 64, 11 bytes

0 sys64738

This is from the BASIC prompt. Or...

Commodore 64, 6502 assembly, 3 bytes (assembled), 16 bytes (source)

*=8000
JMP $FCE2

Answer 14

C++, 51 40 bytes

-11 bytes thanks to Ingve!

#include<os>
int main(){OS::shutdown();}

Only works in IncludeOS (v0.10.0-rc.1)

Test:

$ pwd
/home/simon/IncludeOS/examples/demo_service

$ cat service.cpp
#include<os>
int main(){OS::shutdown();}

$ mkdir build && cd build && cmake .. && make && cd ..
[...]

$ boot build/IncludeOS_example
[...]
================================================================================
================================================================================
 IncludeOS v0.10.0-rc.1-9-g151a2b9
 +--> Running [ IncludeOS minimal example ]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

$

Answer 15

TI-Nspire CX CAS, 3 bytes

" "+" "

summing two empty strings.

On an older version of the calculator, this would crash the device and cause it to reboot (there's no way to shutdown a device without reboot apart from physical button combinations).

Video by Adriweb

Answer 16

AppleScript, 30 bytes

tell app "Finder" to shut down

Does exactly what it says: tells Finder to shut the computer off.

Answer 17

AutoHotkey, 11 10 Bytes

Saved a byte thanks to Gurupad Mamadapur

Shutdown,9

AHK Supports a Shutdown command by default. The 9 is a flag, consisting of Shutdown=1 + PowerDown=8.

Answer 18

Machine code (x86, boot loader) 18 bytes

b8 01 53 33 db cd 15 b8 07 53 bb 01 00 b9 03 00 cd 15

Disassembly:

mov ax, 0x5301 ; connect to real-mode APM services
xor bx, bx     ; device id 0 - APM BIOS
int 0x15       ; call APM
mov ax, 0x5307 ; set power state
mov bx, 0x0001 ; on all devices
mov cx, 0x0003 ; to Off
int 0x15       ; call APM

You can test it in Bochs' debugger with the following commands (after starting simulation, having some disk drive set up):

pb 0x7c00
c
setpmem 0x7c00 4 0x335301b8
setpmem 0x7c04 4 0xb815cddb
setpmem 0x7c08 4 0x01bb5307
setpmem 0x7c0c 4 0x0003b900
setpmem 0x7c10 2 0x15cd
c

This same machine code will also work as a DOS executable (*.COM).

Answer 19

C#, 79 54 53 bytes

This works on Windows.

79 bytes:

class _{static void Main(){System.Diagnostics.Process.Start("shutdown","/s");}}

53 bytes, thanks to TheLethalCoder:

_=>System.Diagnostics.Process.Start("shutdown","/s");

Answer 20

AutoIt, 11 bytes

Shutdown(1)

Shutdown function gets combination of following codes

0 = Logoff
1 = Shutdown
2 = Reboot
4 = Force
8 = Power down
16= Force if hung
32= Standby
64= Hibernate

To shutdown and power down, for example, the code would be 9 (shutdown + power down = 1 + 8 = 9).

Answer 21

Windows - NativeAPI, 212 bytes

Ok this is not really the shortest version. But maybe interesting to some. This will not execute on the Win32 subsystem. However it will run when executed within the context of the native api (like autochk.exe does)

Code

#define WIN32_NO_STATUS
#include <windef.h>
#include <winnt.h>
#include <ntndk.h>
NTSTATUS main() {
RtlAdjustPrivilege(SE_SHUTDOWN_PRIVILEGE,TRUE,FALSE,NULL);
return ZwShutdownSystem(ShutdownPowerOff);
}

Build

To build this either use the WinDDK build.exe tool (with an appropriate source file for NMAKE)

Or use these commands to compile and link:

cl /Gd /D_X86_ /showIncludes /I%DDK_INC_PATH% /I%CRT_INC_PATH% /c main.c
link /verbose /nodefaultlib /subsystem:native /machine:X86 /entry:NtProcessStartup@4 C:\WinDDK\7600.16385.1\lib\win7\i386\nt.lib C:\WinDDK\7600.16385.1\lib\win7\i386\ntdllp.lib C:\WinDDK\7600.16385.1\lib\win7\i386\BufferOverflow.lib .\main.obj 

Note: This will build an x86 native executable. Change the appropriate bits if you want to build this for a different architecture.

Test

To test a native executable you have to execute it before the win32 subsystem is loaded. One common way to do it is to append the executable in the following registry key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\BootExecute

Warning

If you do this however, you need to have an option to edit the registry hive of the target OS from another OS. Since you will not be able to boot the target OS anymore!

I did it on a VM where i could easily revert to a previous snapshot!

Answer 22

Groovy, 23 bytes

'shutdown /p'.execute()

Answer 23

AppleScript, 44 bytes

tell application "Finder"
shut down
end tell

I don't know how AppleScript syntax works or anything, so if anybody knows how to shorten this, please tell.

Also, I'm doing this on my phone at school ("hacking"), so I can't test it.

At 14 fewer bytes (thanks to kindall) you can say

tell app "Finder" to shut down

Answer 24

Most Linux shells, 15 bytes

# echo o>/p*/*ger

It could be made to be 11 bytes long, if you happen to be in the /proc directory:

# echo o>*ger

This is very straightforward (has no side effects, like unmounting filesystems or killing processes) and rather brutal.

Answer 25

Android shell, 9 bytes

reboot -p

Answer 26

J, 14 bytes

2!:0'poweroff'

Works on Linux systems. 2!:0 executes the string in /bin/sh.

Answer 27

Clojure, 40 39 bytes

(.exec(Runtime/getRuntime)"shutdown/s")

-1 byte by changing the flag from -s to /s, which allowed me to get rid of the space.

Basically the Java answer.

Testing this was fun. Windows decided to do a firmware update on my Surface the second it shut down. Of course.

(defn shutdown []
  (.exec (Runtime/getRuntime) "shutdown -s"))

Answer 28

C++, 48 47 (Windows) 46 45 (Linux) bytes

Removed 1 byte thanks to Snowman

#include<cstdlib>
main(){system("shutdown/p");}

This should shutdown the system for windows

#include<cstdlib>
main(){system("poweroff");}

This should shutdown the system for Linux

Answer 29

Node.js, 39 bytes

Linux

require('child_process').exec('init 0')

Answer 30

Bash 15 bytes

shutdown -h now

alternatively : init 0

Answer 31

Mathematica on Windows 16 Bytes

Invoke the shell command with Run.

Run@"Shutdown/p"

Answer 32

AHK, 19 15 bytes

Run,Shutdown -s

Works on windows only.

Answer 33

R, 20 19 bytes

shell("shutdown/s")

---

Previous answer :

system("shutdown/s")

Answer 34

TI-Basic, 3 bytes

ClrHome:"

Basically, this displays a blank screen and then waits for automatic timeout to kick in and shutdown the calculator, although you will not notice when this happens. The blank screen resembles a shutdown so you will not notice when the device actually shuts down.

Answer 35

PHP, 20 bytes

shell_exec("init 0");

Answer 36

DOS 7.1 (Windows 98) command prompt/batch, 5

WIN/P

Only works from real mode (MS-DOS command prompt).

Answer 37

Assembly (Z80, Amstrad CPC), one byte

Amstrad CPC cannot be physically shut down by software, but system can be reset.

The following one-byte assembly program is enough to reset system:

C7    ;RST 0

It is a valid assembly program (in RAM) since no header of any kind is needed on this system.

You can install this program from BASIC e.g.:

poke 999,&c7

Then call it:

call 999

Can I haz test?

You can test at once on CPCBox - Amstrad CPC emulator in Javascript.

Answer 38

Lisp, 38 bytes

(trivial-shell:shell-command "init 0")

Answer 39

Alternative Python on Linux + SysRQ, 47 42 bytes:

open("/proc/sysrq-trigger","w").write("o")

Can be run either from python -c or from script, and requires root privileges to write to the file. The idea isn't python-specific. Writing to that file on Linux can be done in any other way - bash, perl, ruby , etc.

Note that this isn't a graceful shutdown, so expect that there is potential for data to be lost. See the Wikipedia article for more info on sysrq keys.

Answer 40

EthOS Shell - 1 byte

Just type the letter r to reboot, i.e.:

r

Answer 41

Python 3, 53 bytes

import subprocess
subprocess.call(["shutdown", "/s"])

This does give a window and shutdown warning. If you wanted to shut it down immediately then you would use "/p".

You could also call the function from the USER library but this is a longer solution than the submitted version.

Answer 42

JScript, 53 bytes

new ActiveXObject('WScript.Shell').Run("shutdown /s")

JScript is Microsoft's implementation of JavaScript. Run with wscript scriptname.js.

Answer 43

VBScript, 46 bytes

CreateObject("WScript.Shell").Run "shutdown /s"

Run with wscript scriptname.js.

Answer 44

Amstrad CPC Basic, 7 keypresses.

Amstrad CPC cannot be physically shut down by software, but system can be reset with this BASIC call:

call 0

How it works

General info

At the beginning of memory (either RAM or ROM, both are prepared for this), there is a table for Z80 RST instruction. These instructions, related to Z80 interrupt handling, are also used (even on machines other than Amstrad CPC, like TI-81) for other tricks because one-byte long assembly instruction is enough to reach any of the 8 entries.

On the Amstrad CPC they are used to space-efficiently call code in ROM, RAM, expansion RAM/ROM, see BIOS Function Summary - CPCWiki or ref page 8+. This is used extensively to make RAM-based indirections that allow easily calling ROM routines from RAM (even from BASIC, like call &bd19 that waits for screen refresh) and also, by changing them, modifying system behavior even though system is in ROM (like changing how text is displayed, or even redirecting it to printer by changing two bytes of RAM). See BB00 and following in BIOS Function Summary - CPCWiki or Firmware Guide

Specific use

Entry zero jumps to a ROM-base routine that performs full machine reset. The simplest way to call it from BASIC it call 0.

Variant

If you insist on a program that can be run rather than a direct command, it takes 8 keypresses:

1call 0

Then you can run.

Can I haz test?

You can test at once on CPCBox - Amstrad CPC emulator in Javascript.

Answer 45

Commodore 128 (from native mode), 6 characters including user response and return

GO64

You will then be prompted with:

ARE YOU SURE? 

Press Y and enter. This shuts down the C128 native mode (I know it doesn't power off the computer, but that's as close as I can get).

Answer 46

Machine code (x86 boot loader), 2 bytes

fa f4

Disassembly

cli ; disable all maskable interrupts
hlt ; stop the processor until an interrupt or hard reset happens

The HLT instruction causes the CPU to stop execution and enter low-power mode, until any interrupt (maskable or NMI) or hard reset happens. This doesn't power off the whole system, but the original IBM PC didn't have any way to power off without the user mechanically pressing the switch. Also, if there happens an NMI, and its handler returns, the program will resume and execute arbitrary code which happens after f4. This is unlikely though, since NMI usually signals about hardware faults.

This same code will work as a DOS .COM program.

Answer 47

Perl 5 (on a unix-like OS), 6 bytes

`halt`

Requires you to be root.

Answer 48

Jelly, 25 bytes

It makes use of the undocumented monad ŒV, which takes a list, concatenates it and evaluates it using Python's eval.

“WƒuUḤøMŒƁEḄV#ẆṄⱮṁƬṅȯV»ŒV

The compressed string translates to import os;os.system("poweroff") so it only works on Linux (with root). The following code was used for compressing.

Compress().dictionary('import')
          .string(' os;os.')
          .dictionary('system')
          .string('("')
          .dictionary('power')
          .dictionary('off')
          .string('")').go()

By changing the poweroff it can be extended to other systems (but power and off are in the dictionary so this will probably be the shortest). For example, following 33-byte version worked on a Mac.

“¡Ṁ\\meṾṭ£ȧ+⁾⁸}ḶṠȯƇọṣỴ\\Ḃ⁴8ġṢṾ»ŒV

Answer 49

shortC, 10 bytes

A$shutdown

Explanation/ungolfed:

A           main function
 $          execute system command
  shutdown  shutdown

Answer 50

AppleScript (45 bytes)

tell application "System Events" to shut down

Answer 51

Vimscript (Linux Bash) 8 bytes

:!init 0

Vimscript (Windows CMD) 12 bytes

:!shutdown/p

Vimscript (Windows PowerShell) 15 bytes

:!Stop-Computer

Two dots : are required for the vim command, and the '!' redirects the command to the shell runing behind. You may require some extra permissions for this to work.

Answer 52

AWK, 39 bytes

#!/bin/awk -f
BEGIN{"poweroff"|getline}

Assumes running on Linux and that AWK is located at /bin/awk and that the poweroff command is in the users path.

Since it uses the BEGIN block, no input is necessary. It simply pipes the output of the poweroff command into getline which it precedes to ignore.

Should work for Windows users provided they are in an environment similar to Cygwin.

Answer 53

C, macOS, 18 bytes

main(){reboot(8);}

This is not a proper shutdown. Usual caveats apply. On my MacBook Air, this resulted in a black screen with a spinning indicator, then a shutdown after a few seconds.

x64 Assembly, macOS, 11 bytes (untested)

From disassembling the reboot function in libSystem:

movl    $0x2000037, %eax   # b8 37 00 00 02
pushq   $0x08              # 6a 08
popq    %r10               # 41 5a
syscall                    # 0f 05

Answer 54

Perl 5.x (on CentOS Linux), 27 bytes

system("shutdown -h now");

Make system call to shutdown in Linux to halt (-h) now.
Changing -h to -r will shutdown then reboot Linux.

Answer 55

AutoIt (windows), 11 bytes:

Shutdown(1)

Answer 56

Python, 53 bytes

import subprocess
subprocess.call(["shutdown", "/s"])

Pretty simple code but can do some damage if you haven't saved anything.

Breakdown

import subprocess

This imports the subprocess module that comes with Python that can be used across the script.

subprocess.call(["shutdown", "/s"])

subprocess.call runs a process as if you pressed Win + R. It requires a list of strings that will be joined with a space between them and executes it on the PC's shell.

Answer 57

VBA (32-Bit, Windows Only), 72 Bytes

An anonymous VBE immediate function that calls the declared windows function ExitWindowsEx from user32.dll.

To be clear, this requires a 32-Bit version of MS Office, not a 32-Bit version of Windows

Declared Function

Declare Sub ExitWindowsEx Lib"user32"(ByVal A&,ByVal B&)

Anonymous VBE immediate window function

ExitWindowsEx 1,0

Answer 58

Burlesque - 22 bytes

"cmd"{"shutdown /s"}ex

Obviously you can not try this online.

On linux you can probably get away with "shutdown"ex if your distro offers the shutdown util.

Answer 59

UEFI Shell - 16 bytes

reset -s

In ASCII it would be 8 bytes but since UEFI uses UCS-16, every character takes up 2 bytes.

Answer 60

05AB1E (legacy) prior to commit June 4th, 2018, 10 bytes

’À…„‹/p’.E

Try it online without the .E.

Explanation:

In the commit of June 4th, 2018, the builtin .E has been changed from run_as_Bash_code to run_as_Python_code. So this only works prior to this commit.

’À…„‹/p’    # Push dictionary string "shutdown/p"
        .E  # Run it as Bash code

05AB1E, 25 bytes

’£Ø os;os.‚«('À…„‹/p')’.E

Try it online without the .E.

Explanation:

The .E builtin is eval_in_Python in the current version of 05AB1E.

’£Ø os;os.‚«('À…„‹/p')’    # Push dictionary string "import os;os.system('shutdown/p')"
                       .E  # Evaluate as Python code

See this 05AB1E tips of mine (section How to use the dictionary?) to understand why ’À…„‹/p’ is "shutdown/p" and ’£Ø os;os.‚«('À…„‹/p')’ is "import os;os.system('shutdown/p')".

Note: Both work only on Windows. Could be modified to also work on other OS, i.e. "init 0".E and ’£Ø os;os.‚«('„‡ƒŸ')’.E for Linux.