Shortest code for infinite disk I/O

Question

(Just open 50 tabs in Google Chrome :D (just kidding, no you can't))

Shortest code for infinite disk I/O any language, C# example:

using System.IO;

namespace FileApp {
    static class Program {
        public static void Main() {
            do {
                File.WriteAllText("a", "a");
                File.Delete("a");
            } while (true);
        }
    }
}

You can't just fill the entire disk though, as then it would halt in the end and would be finite.

And you can't do reading only, infinite writing has to happen. (It has to kill my SSD after enough runtime.)

Get cracking! :)

Answer 1

DOS/Batch: 4 bytes

%0>x

This batch file will call itself (%0) and redirect (>) the output to a file called x. Since echo is on by default, this will output the path and command.

Answer 2

PowerShell v2+, 10 bytes

for(){1>1}

Simply loops infinitely with an empty for loop. Each iteration, we output the integer 1 (implicitly converted to a string) with the > redirect operator, which overwrites the file named 1 in the local directory.

Answer 3

Pyth, 6 bytes

#.w]]0

Pyth's only file output command is .w. When called on a string, it writes that string to a file in append mode, which is no good for the purpose of this question. When called on a 2-d array, it writes the corresponding image to that file, overwriting the file contents. That's what this program does. The default file output name is o.png, so this program infinitely overwrites the file o.png with a 1-pixel white image. # is an infinite loop.

Answer 4

If you want a shorter (but more boring than my other one) answer:

Bash, 5 bytes

>w;$0

I could make that shorter if there's a command (less than 3 bytes long) that writes something to disk I/O. Something like sync would work, but sync is 4 bytes

Note: this doesn't work when run straight from bash, only when put in a script and run as the script name. (i.e. echo 'w>w;$0' > bomb; chmod 755 bomb; ./bomb)

Answer 5

Ruby, 22 20 bytes

loop{open(?a,?w)<<1}

Repeatedly truncates and writes a 1 to the file a.

Thanks to Ventero for 2 bytes!

Answer 6

cmd, 14 bytes

:a
cd>1
goto a

Infinitly overwrites the file 1 with the string to the current directory

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I'm new here: Are windows new lines (CR LF) counted as two bytes?

Answer 7

Bash + coreutils, 10

yes \>b|sh

Writes a continuous stream of >b, which is piped to sh for evaluation. >b simply truncates a file called b to zero bytes each time.

Answer 8

Perl 5, 27 32 22 bytes

{{open my$h,'>o'}redo}

If simply changing the modification timestamp of a file suffices...

Quick explanation:

{ # Braces implicitly create/mark a loop.
    { # They also create closures, for `my` variables.
        open my $filehandle, '>', 'o';    # Writing to file "o".
        # close $filehandle;   # Called implicitly when
                               # variable gets destroyed.
    } # $filehandle gets destroyed because there are no references to it.
    redo; # ...the loop.
}

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Previous solution (32 bytes): {{open my$h,'>o';print$h 1}redo}

Edit: {open F,'O';print F 1;redo} ← Didn't test the code before posting; now I had to correct it.

Answer 9

PHP, 60 30 17 16 15 bytes

Updated yet again as per @manatwork suggested:

while(!`cd>1`);

Also now tested.

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A bit of cheating 22 bytes:

while(exec('>1 dir'));

Earlier suggestion by @manatwork 30 bytes:

while(file_put_contents(1,1));

NOT TESTED (no php available on this computer) 43 bytes:

for($a=fopen(1,'w');fputs($a,1);fclose($a))

A golfed original 45 bytes:

$a=fopen(1,'w');while(fputs($a,1))rewind($a);

My first post here, joined because I just had to try this out: as long as file write succeeds, rewind file pointer to start.

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Just can't get smaller than the file_put_contents().

Answer 10

C, 95 94 93 89 78 90 89 76 75 bytes

#include<stdio.h>
main(){for(FILE*f=fopen("a","w");;fputc(0,f),fclose(f));}   

Again, sudo watch -n1 lsof -p `pidof inf` seems to say this is valid.

^{HOW DID I NOT SEE THAT SPACE D:<}

Thanks @Jens for shaving off 13 bytes :D

Answer 11

sh, 11 bytes

w>w;exec $0

Save this to a file without special characters, such as loop.sh, make it executable, and run it with ./loop.sh or similar.

This writes the output of the command w to the file w, overwriting the previous value each time. Then, it replaces itself with a fresh version of the same program, so it can run infinitely.

Answer 12

CPython 3.5, 33 16 bytes

while 1:open("a")

Yes, really. :D

Answer 13

Bash, 26 bytes

yes>y&while :;do rm y;done

If I were to expand this one-liner, I would get this:

yes > y &      # Write out infinitely to the file y in the current directory
while true     # Let's do something forever
do             # Here's what we're going to do
    rm y       # delete y
done           # That's all we're going to do

This can't exactly compete with the 10 byte PowerShell line, but it'll hold its own against the others. See my other answer for the 6 byte version.

Answer 14

TI-BASIC, 12 bytes

While 1
Archive A
UnArchive A
End

Alternate solution by user lirtosiast with the same size:

While 1
SetUpEditor
Archive ∟1
End

This will work on the TI-83+ and TI-84+ series of calculators.

Yes, this also works if A is already archived or is not initialized at all at the start of the program! The program is only 12 bytes because of tokenization.

Answer 15

MATL, 10 bytes

`1[]T3$Z#T

Explanation

This is an infinite loop that writes number 1 to a file called inout in current directory, overwriting previous file's contents.

`       % do...while loop
  1     %   push number 1
  []    %   push empty array
  T     %   push "true"
  3$Z#  %   fwrite function. First input is file content. Second is file name;
        %   defaults to "inout" if empty. Third indicates that any previous
        %   file contents should be discarded
  T     %   push "true": loop condition 
        % implicitly end loop. Loop condition is "true", so the loop is infinite

Answer 16

Haskell, 20 bytes

f=writeFile"b""a">>f

Write the string "a" to a file named "b" and repeat. writeFile overwrites the file if it exists.

Answer 17

ZSH, 14 bytes

for ((;;)) :>:

Zsh, unlike Bash and other Bourne-like shells, allows loops without the do ... done fence, provided the condition is suitably delimited.

Alternatively, with while:

while {} {:>:}

Note that : is a builtin. You can't suspend this loop.

The principle is the same as in Digital Trauma's answer - nothing is written to the file, the IO is purely from creating and truncating the file.

Answer 18

JavaScript (Node.js), 43 41 bytes

(c=x=>require("fs").writeFile("a",x,c))()

Writes null to a file named a, then repeat.

Answer 19

Rust, 84 Bytes

fn main(){loop{use std::io::Write;std::fs::File::create("a").unwrap().write(b"a");}}

File::create truncates an existing file, thus ensuring that we don't run out of disk space.

The used Compiler (1.9 Nightly) issues a warning about the unused result of write(...) but compiles nevertheless.

Answer 20

C, 92 bytes

#include <stdio.h>
main(){for(FILE*f=fopen("a","w+");fprintf(f," "),!fclose(f);;);return 0;}

While it looks like you could save 1 byte by

  for(FILE*f=fopen("a","w+");fprintf(f," ")+fclose(f);;){}

the problem with that loop is that + doesn't give you the guaranteed order.

Or recursive - shouldn't overflow if the compiler properly implements tail recursion (f is in an explicit inner scope)

85 bytes

#include <stdio.h>
main(){{FILE*f=fopen("a","w+");fprintf(f," ");fclose(f);}main();}

Answer 21

Mathematica, 14 bytes

For[,1>0,a>>a]

Repeatedly writes the string "a" to a file named a in the current directory, creating it if it doesn't exist.

Answer 22

C, 40 bytes

main(){for(;;)write(open("a",1)," ",1);}

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It will quickly run out of file descriptors, though; this can be overcome with:

45, 43 bytes

main(f){for(f=open("a",1);;)write(f,"",1);}

Answer 23

C on amd64 Linux, 36 bytes (timestamp only), 52 49 bytes (real disk activity)

I hard-code the open(2) flags, so this is not portable to other ABIs. Linux on other platforms likely uses the same O_TRUNC, etc., but other POSIX OSes may not.

+4 bytes to pass a correct permission arg to make sure the file is created with owner write access, see below. (This happens to work with gcc 5.2)

somewhat-portable ANSI C, 38/51 bytes (timestamp only), 52/67 bytes (real disk activity)

Based on @Cat's answer, with a tip from @Jens.

The first number is for implementations where an int can hold FILE *fopen()'s return value, second number if we can't do that. On Linux, heap addresses happen to be in the low 32 bits of address space, so it works even without -m32 or -mx32. (Declaring void*fopen(); is shorter than #include <stdio.h>)

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Timestamp metadata I/O only:

main(){for(;;)close(open("a",577));}   // Linux x86-64

//void*fopen();       // compile with -m32 or -mx32 or whatever, so an int holds a pointer.
main(){for(;;)fclose(fopen("a","w"));}

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Writing a byte, actually hitting the disk on Linux 4.2.0 + XFS + lazytime:

main(){for(;write(open("a",577),"",1);close(3));}

write is the for-loop condition, which is fine since it always returns 1. close is the increment.

// semi-portable: storing a FILE* in an int.  Works on many systems
main(f){for(;f=fopen("a","w");fclose(f))fputc(0,f);}                 // 52 bytes

// Should be highly portable, except to systems that require prototypes for all functions.
void*f,*fopen();main(){for(;f=fopen("a","w");fclose(f))fputc(0,f);}   // 67 bytes

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Explanation of the non-portable version:

The file is created with random garbage permissions. With gcc 5.2, with -O0 or -O3, it happens to include owner write permission, but this is not guaranteed. 0666 is decimal 438. A 3rd arg to open would take another 4 bytes. We're already hard-coding O_TRUNC and so on, but this could break with a different compiler or libc on the same ABI.

We can't omit the 2nd arg to open, because the garbage value happens to include O_EXCL, and O_TRUNC|O_APPEND, so open fails with EINVAL.

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We don't need to save the return value from open(). We assume it's 3, because it always will be. Even if we start with fd 3 open, it will be closed after the first iteration. Worst-case, open keeps opening new fds until 3 is the last available file descriptor. So, up to the first 65531 write() calls could fail with EBADF, but will then work normally with every open creating fd = 3.

577 = 0x241 = O_WRONLY|O_CREAT|O_TRUNC on x86-64 Linux. Without O_TRUNC, the inode mod time and change time aren't updated, so a shorter arg isn't possible. O_TRUNC is still essential for the version that calls write to produce actual disk activity, not rewrite in place.

I see some answers that open("a",1). O_CREAT is required if a doesn't already exist. O_CREAT is defined as octal 0100 (64, 0x40) on Linux.

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No resource leaks, so it can run forever. strace output:

open("a", O_WRONLY|O_CREAT|O_TRUNC, 03777762713526650) = 3
close(3)                                = 0
... repeating

or

open("a", O_WRONLY|O_CREAT|O_TRUNC, 01) = 3
write(3, "\0", 1)                       = 1   # This is the terminating 0 byte in the empty string we pass to write(2)
close(3)                                = 0

I got the decimal value of the open flags for this ABI using strace -eraw=open on my C++ version.

On a filesystem with the Linux lazytime mount option enabled, a change that only affects inode timestamps will only cause one write per 24 hours. With that mount option disabled, timestamp updating might be a viable way to wear out your SSD. (However, several other answers only do metadata I/O).

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alternatives:

shorter non-working:

main(){for(;;)close(write(open("a",577),"",3));} uses write's return value to pass a 3 arg to close. It saves another byte, but doesn't work with gcc -O0 or -O3 on amd64. The garbage in the 3rd arg to open is different, and doesn't include write permission. a gets created the first time, but future iterations all fail with -EACCESS.

longer, working, with different system calls:

main(c){for(open("a",65);pwrite(3,"",1);)sync();} rewrites a byte in-place and calls sync() to sync all filesystems system-wide. This keeps the drive light lit up.

We don't care which byte, so we don't pass 4th arg to pwrite. Yay for sparse files:

$ ll -s a
300K -rwx-wx--- 1 peter peter 128T May 15 11:43 a

Writing one byte at an offset of ~128TiB led to xfs using 300kiB of space to hold the extent map, I guess. Don't try this on OS X with HFS+: IIRC, HFS+ doesn't support sparse files, so it will fill the disk.

XFS is a proper 64bit filesystem, supporting individual files up to 8 exabytes. i.e. 2^63-1, the maximum value off_t can hold.

strace output:

open("a", O_WRONLY|O_CREAT, 03777711166007270) = 3
pwrite(3, "\0", 1, 139989929353760)     = 1
sync()                                  = 0
pwrite(3, "\0", 1, 139989929380071)     = 1
sync()                                  = 0
...

Answer 24

Racket, 46 bytes

(do()(#f)(write-to-file'a"f"#:exists'replace))

Answer 25

SmileBASIC, 12 bytes

SAVE"A
EXEC.

Answer 26

Factor, 73 bytes

USING: io.files io.encodings
[ 0 "a" utf8 set-file-contents ] [ t ] while

Sets the file contents to the nul byte forever.

Answer 27

CBM BASIC 7.0, 9 bytes

0dS"a":rU

This program, when run, repeatedly saves itself to disk. Here's a more readable version which doesn't use BASIC keyword abbreviations:

0 dsave "a" : run

Answer 28

Python, 32 bytes

while 1:open("a","w").write("b")

Note that if run on python 3, this will produce an infinite number of warnings. Also, it will probably run out of fds if run in a non-refcounting implementation.

Answer 29

Dyalog APL 15.0, 17 bytes (non-competing)

(⊢⊣⊃⎕NPUT⊢)⍣≢'A'1

Chrome currently renders U+2262 wrong. The above line should look like (⊢⊣⊃⎕NPUT⊢)⍣̸≡'A'1.

This is non-competing because version 15 has not been released yet.

Applies ⍣ the function (⊢⊣⊃⎕NPUT⊢) on 'A'1 until the input is changed (i.e. never):

⊢⊣⊃⎕NPUT⊢ is a function train:

┌─┼───┐      
⊢ ⊣ ┌─┼─────┐
    ⊃ ⎕NPUT ⊢

The rightmost ⊢ returns 'A'1 unmodified; this (filename, overwrite-flag) will be the right argument to `⎕NPUT'.

'⊃' returns the first element of 'A'1 ('A'); this is the data to be written.

Then ⎕NPUT is run, and reports how many bytes were written (2 or 3 depending on OS); this becomes the right argument to the ⊣.

The leftmost ⊢ again returns 'A'1 unmodified; this is the left argument to the ⊢.

⊣ ignores its right argument and returns the left argument ('A'1), this becomes the new value fed to ⍣.

Since the new value is identical to the old one, the operation is continued (forever).

Answer 30

Tcl, 36 bytes

set f [open a w]
while 1 {puts $f .}

Try it online!

Answer 31

vim text editor, 10 bytes

qa:w<enter>@aq@a

8 bytes if you do not could the execution command @a

Answer 32

Lua, 39 bytes

while''do io.open('a',"w"):write('')end

Answer 33

C++, 61 bytes. (or 66 bytes to actually hit the disk on Linux+XFS+lazytime)

Timestamp metadata I/O only:

#include <fstream>
int main(){for(;;){std::ofstream a("a");}}

The disk I/O is due to a's mod time changing, which will be written to disk occasionally. (very occasionally with the commonly-use lazytime mount option. Also see my C answer.)

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Write data before closing:

#include <fstream>
int main(){for(;;){std::ofstream a("a");a<<4;}}

Actually hits the disk: lights up my hard drive light. (Linux 4.2.0, XFS, lazytime)

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The ofstream constructor opens the file, and the destructor closes it again. There are no resource leaks, so this will actually run forever without running out of memory, file handles, or disk space.

strace output:

open("a", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3
write(3, "4", 1)                        = 1      # not present with first version
close(3)                                = 0
... repeating

Answer 34

C99, 84 bytes

#include<stdio.h>
int main(){while(1){FILE*f=fopen("a","w");fputc(9,f);fclose(f);};}

If you don't care about buffers, you can do this instead:

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C99, 65 bytes

#include<stdio.h>
int main(){while(1){fputc(9,fopen("a","w"));};}

I don't know if it closes automatically (no file handle), so please comment and I'll edit.

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Lots of \ts to write (relax, they're not infinite!).