Code that will only execute once

Question

Goal

The goal of this challenge is to write code that will execute once and only once. This means basically that it damages the program, script, or environment in some way. If rebooting the system allows the code to run again that is permitted.

Scoring

Number of votes. All assumptions must be clearly listed. Any answers just initiating a reboot or halt will be disqualified.

Additional Rules because Greg Hewgill is a demi-god

No root access is permitted.

End Date

The contest will close on May 31, 2014.

Edit

This contest has been changed to popularity contest.

Answer 1

Here's a couple. Unlike many, these are not destructive, just creative and unorthodox.

Bash

#!/usr/bin/env bash
read <<< ''
printf "$REPLY" > "$0"

This one's pretty simple. The variable $REPLY is created implicitly by read, but filled with an empty herestring. That empty string is then printf'ed into the current script. It is a rather obfuscated equivalent of the following:

#!/usr/bin/env bash
cat <<< '' > "$0" # probably a lot more portable

Windows Batch

copy con %0 < nul

The second one basically copies the console input, read from nul, into the current file.

Answer 2

Minecraft Command Block

setblock ~ ~ ~ air

When you run this in a command block, it destroys itself.

Answer 3

SQL

create proc P as drop proc P

SQL Fiddle

Answer 4

x86 Machine Code (5 bytes)

HEX:

EA0000FFFF

ASM:

JMP FFFF:0000

You can try with debug.exe:

C:\>debug
-a 100
0AE7:0100 jmp ffff:0000
0AE7:0105
-g=100

Explanation: BIOSis always at FFFF:0000 in memory. So this sequence boots the computer, if this is run in a protected command prompt in Windows it makes that process unresponsive.

Answer 5

ARM Linux full standalone ELF, 50 46 45 bytes

7f 45 4c 46 01 00 00 00  00 00 00 00 00 00 01 00
02 00 28 00 21 00 01 00  21 00 01 00 04 00 00 00
01 98 0a 27 00 df 01 27  00 df 20 00 01

Adapted version of the code used in A Whirlwind Tutorial on Creating Really Teensy ELF Executables for Linux.

Assembler source (with raw encoded ELF header and comments, most of which are the same as in the article)

@ Adaptation of
@    https://www.muppetlabs.com/~breadbox/software/tiny/teensy.html
@ for an ARM binary which deletes itself. XD
@ $ arm-none-eabi-as -march=armv4t -mthumb runonce-arm.s -o runonce-arm.o
@ $ arm-none-eabi-ld -Ttext 0x00010000 runonce-arm.o -o runonce-arm.elf
@ $ arm-none-eabi-objcopy -O binary runonce-arm.elf runonce-arm

        .text              @ A lie.
        .arch   armv4t     @ Set architecture version
        .thumb             @ Needs to be Thumb to fit. ARM is too thicc.
        .syntax unified
        .org    0          @ Start at offset 0
Elf32_Ehdr:
        .byte   0x7F,'E','L','F'            @ e_ident
Elf32_Phdr:
        .word   1                                           @ p_type
        .word   0                                           @ p_offset
        .word   0x00010000 @ same as -Ttext                 @ p_vaddr
        .short  2          @ ET_EXEC        @ e_type        @ p_paddr
        .short  40         @ EM_ARM         @ e_machine
        .word   _start                      @ e_version     @ p_filesz
        .word   _start                      @ e_entry       @ p_memsz
        .word   4          @ Elf32_Phdr     @ e_phoff       @ p_flags

        @ Here is some space to put our code in.
        .thumb_func
        .globl _start
 _start:
        @ r0 = argv[0] from _start state
        ldr     r0, [sp, #4]                @ e_shoff       @ p_align
        @ unlink(argv[0])
        movs    r7, #0x0a  @ unlink
        svc     #0         @ syscall        @ e_flags
        @ exit(dontcare)
        movs    r7, #0x01  @ exit
        svc     #0         @ syscall        @ e_ehsize
        @ unreachable

        @ finish the header
        .short  0x20                        @ e_phentsize
        .byte   1                           @ e_phnum
        @ Truncated header because for some reason, Linux accepts this.

Basically, I took this program:

#include <unistd.h>
int main(int argc, char *argv[])
{
    unlink(argv[0]);
}

Or if it is easier to read,

main(c,v)int*v;{unlink(*v);}

And squeezed it into an ELF header using the method in that article, so it is 45 bytes with no dependencies on libc.

Works every time except when it is called from $PATH.

Answer 6

Error safe termination (Python 2/3)

from contextlib import contextmanager
@contextmanager
def suicide():
    try:    yield
    finally:
        open(__file__    , 'w')
        open(__file__+'c', 'w')

#-------------------------------------
# Error safe code ;)
#-------------------------------------
with suicide():
    print("Goodbye cruel world!")
    jump_off_building_______crash

Answer 7

Ruby, 15 14

Put this line to a file (del.rb):

File.delete $0

then run it (self-destructive) : ruby del.rb del.rb

Answer 8

PHP - 23

<?=fopen(__FILE__,'w');

Answer 9

Coffescript

_=->_=1

compiles to:

var _;

_ = function() {
  return _ = 1;
};

Answer 10

𝔼𝕊𝕄𝕚𝕟 (noncompetitive)

ɟ`html”Ĭ)

Try it here (Firefox only).

Translates to $('html').remove() in Javascript.

Answer 11

R, 7 Bytes

`=`=`$`

The code makes the "=" (used for assigning) become the "$" (used for subseting). After that it gives error.

Answer 12

Bash: 4 chars

rm a

Put this in a file named a and run it on your Linux machine.

Answer 13

Plain TeX - 31 (24) chars

\openout1=\jobname\write1{}\bye

If you save it as file a.tex then:

\openout1=a\write1{}\bye

Answer 14

Bash

This deletes the file and makes sure that you can't recover it. So it definitely can't execute more than once.

shred "$0"

shred is a program to securely delete files by overwriting them. It's in coreutils.

Answer 15

AutoHotKey, 39 bytes

FileDelete %A_ScriptDir%\%A_ScriptName%

(Yes, I'm aware this is an ancient thread)

Answer 16

Dyalog APL (non-competing because it is too late)

f←⎕EX'f'∘⊣

f can only be called once. It needs an argument, which is ignored:

      f←⎕EX'f'∘⊣
      f 'dummy argument'
      f 'dummy argument'
VALUE ERROR
      f'dummy argument'
     ∧

It is a so-called "atop", which is a train of two functions. The left one is applied on the result of the right one.

The right function is 'f'∘⊣ which replaces any given argument with the string 'f'.

The left function is ⎕EX, which EXpunges the object named in its argument.

The first time around, 'f'∘⊣ returns 'f', which causes ⎕EX to erase f. The second time around, calling f results in an error because f does not exist.

---

Here is one that can be tried online:

f←{f∘←¨}

After defining the function, the first time that it is called (with a dummy argument), e.g. f 4, the function ignores the argument, and instead redefines itself to be an operator (higher-order function). Now, operators need at least a left operand so when it is called again, the call will fail with a syntax error.

Answer 17

Linux, 8 bytes

killall5

Similar to this answer, but this works on pretty much any Linux since System V and you don't need to be root. Don't believe me? Try it out on your Linux system! You'll want to save any work first...

I actually found this by accident when I was 11 messing around with Linux for the first time.

Links: killall5 manpage, recording

Answer 18

Commodore 64 BASIC, 7 bytes

POKE 1,3

I've had a lot of fun in various BASIC dialects POKE-ing around in the first few memory storage locations. Here's the effect of this one:

Try it online! You'll have to type it in yourself.

Some other POKEs:

• POKE 1,1 will freeze the system.
• POKE 1,2 will clear the screen.
• POKE 1,4 completely kills the system - the power button won't even work.
• POKE 1,5 through POKE 1,9 do the same as POKE 1,4, but with varying levels of destruction.

Answer 19

TIS-100, 6 bytes

@0
HCF

The HCF (or halt and catch fire) command instantly crashes the TIS-100. The only way to run it again is to start it up again.

Answer 20

R16K1S60 Assembly

mov [ax], ax

Simply overrides itself with with the contents of AX. the mov instruction is only one word large, so it deletes itself. Depends on AX being 0 (most releases guarentee this)

Safe version

mov [0], ax

Depends on ax not being this specific instruction

Answer 21

Wolfram Language (Mathematica): 37 Characters

Export[#,""]&/@FileNames[All,"C:/",∞]

Never tested this fully, but it should overwrite every single file on a Windows computer, including the Mathematica installation and the file the program is saved in by replacing all data with an empty string. Actually useful for quickly clearing out a folder, but most definitely not something I want to run.

Answer 22

Haskell - 80 bytes

Pre base-4.6.0.0 : May not work on Windows. This depends on how the program is invoked.

import System.Environment
import System.Directory
main=getProgName>>=removeFile

Post base-4.6.0.0 : A bit longer but always works.

import System.Environment
import System.Directory
main=getExecutablePath>>=removeFile

Answer 23

JAVASCRIPT (35 26 bytes when minified, in case that matters.) I know this is a late entry, but I had a situation where I considered being able to kill a function and decided it'd make a good entry here. (Still not sure if I'll actually use it.)

funny = function(){
  alert(0);
  window.funny = '';
};

funny();
funny();

minified

a=function(){alert(0);window.a=""};

Alert isn't really needed

a=function(){window.a=""};

Answer 24

Python 2.7

import inspect
import os
for x in range(0, 2):
    os.remove(inspect.stack()[0][1])
    print "am I dead yet?"

It only runs 1/2 of a time.

Answer 25

Shell script (Linux Bash); 4 characters

rm *

Warning ! Don’t try this at home.

This shell script can be run only once. When run, this shell script will self-destruct.

Answer 26

C, 56 chars

x[9];main(c,v)int**v;{sprintf(x,"rm %s",*v);system(x);}

Run on a UNIX system. By convention, the first string param passed to a C program is the executable name. This program simply deletes the executable (but leaves the source, which you have to recompile to run it again).

Answer 27

oldschool DOS

---

You don't even need a compiler or interpreter, just the prompt. Not even reboot will let it run again once it completes (note: do not try on something you don't want to sacrifice. OS likely won't boot either.)

deltree C:\

Answer 28

Windows batch, 4 bytes

.>%0

This will attempt to execute '.' as a command, while redirecting stdout to the original file, resulting in destruction of the original file.

Answer 29

Scratch, 49 bytes

when gf clicked
wait until<(n)<(1
change[n v]by(2

Assuming n=0, which is the initial state of a variable when it is created.

Answer 30

Python 24

Name the file 'q'

import os
os.remove("q")