65

I have a Windows XP box (NTFS filesystem) on which I found a file named NUL. I have not been able to remove this file in any usual way. The file appears to be owned by Administrator in the SYSTEM group, unlike any other file in the same directory (the other files are owned by my user id).

How do I get rid of this file? Where did it come from?

Greg Mattes
  • 3,302
  • 5
  • 25
  • 22
  • 3
    NUL is a system reserved word; see this [Wikipedia article](http://en.wikipedia.org/wiki/Device_file#Device_files). A file named NUL should never exist on the filesystem; this may be caused by buggy software. You may be able to remove it using the `DELETE` command using Command Prompt. – bwDraco May 11 '11 at 17:30
  • 11
    @DragonLord: The *filesystem* doesn't have a problem with such names; for example, you can create such files within a POSIX environment. (One can find `aux.c` and similar names in software source code.) It's purely the Win32 API that manages these "device names". – u1686_grawity May 12 '11 at 05:17
  • 1
    The same applies to CON, PRN, AUX, NUL, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, LPT9, and CLOCK$ plus a few others - see http://en.wikipedia.org/wiki/Filename#Comparison_of_filename_limitations – robocat Apr 30 '15 at 01:38
  • 2
    Cygwin creates (or used to) a file called "nul", usually seen in "C:\cygwin\dev\nul". This is the one that I hit once every few years, I Google, and I'm brought back (again) to this question. – zarchasmpgmr May 15 '17 at 19:35

6 Answers6

106

Try

Del \\?\C:\My\Path\NUL

in the command prompt.

See this Microsoft Support article for details: You cannot delete a file or a folder on an NTFS file system volume, under "Cause 5: The file name includes a reserved name in the Win32 name space".

bwDraco
  • 45,747
  • 43
  • 165
  • 205
user541686
  • 23,663
  • 46
  • 140
  • 214
  • 1
    Thanks! That worked! Also, thanks for the great reference to the authoritative documentation. I found something in a web search that was very similar, but did not work. That suggestion had a `.` in place of the `?`. – Greg Mattes May 11 '11 at 20:12
  • 1
    @Greg: Sure! The documentation was @DragonLord's help. :-) And yeah, putting `.` instead of `?` doesn't quite do the same thing -- the question mark prevents further processing by the subsystem, whereas the period means "the current machine"... not quite the same thing, although it's definitely confusing. :) – user541686 May 11 '11 at 20:23
  • 1
    I'm not sure it actually means that. The `\\.\ ` prefix is for [the device namespace](http://msdn.microsoft.com/en-us/library/aa365247%28v=vs.85%29.aspx), but there is no explicit mention that `.` has the same meaning ("current X") as it does for directory names. – u1686_grawity May 12 '11 at 05:15
  • @grawity: Whoops good point, it's an alias for the \DosDevices\ namespace, my bad. – user541686 May 12 '11 at 05:44
  • 5
    As an alternative to above solution if your working directory is already the directory with the `nul` file, you can: `del "\\?\%CD%\nul"` The `%CD%` part is expanded to the working directory and the double quotation marks (`"`) make it all handle also pathnames with "odd" symbols, e.g. `"\\?\C:\path,with\comma\nul"`. – HenrikB Sep 07 '13 at 15:09
  • 1
    It did not not seem to be effective from powershell or an administratively elevated prompt in my environment, but worked effectively in a standard terminal. – JustinC Sep 26 '13 at 21:43
18

Alternatively if you have Cygwin installed, you may want to know, that it has no problem with such files or folders. Particularly,

rm -r /cygdrive/c/path/to/the/file/or/folder/you/want/to/delete

typed in the Cygwin terminal deletes the file or folder named nul or a folder, containing it. This is also applicable to other special file names such as CON, PRN, AUX, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8.

fiktor
  • 773
  • 3
  • 10
  • 19
  • 4
    also works with git bash – c33s Sep 20 '16 at 10:24
  • 1
    If you have installed Git then you've got the GNU `rm` command so you don't need cygwin. Assuming you add the GNU tools bin directory to your PATH you can use all the GNU goodies from cmd. – icc97 Nov 27 '17 at 23:33
  • Thanks for posting this, I mainly use cygwin so it's much more convenient for me to use than the CMD way (which is also perfectly valid, ofc). – Alexander Revo Aug 17 '23 at 14:18
11

I'm adding this here because it is high in the google results and I had a similar issue for a folder named NUL. Unfortunately the above fixes didnt help. Neither did a ton of other stuff I looked at.

I tried rmdir\\?\C:\My\Path\NUL and rmdir\\.\C:\My\Path\NUL without any success and also tried several commands using bash from my SourceTree installation. No joy.

In the end I used DIR /X /A from cmd to list the short names in the parent directory. This returned NUL~1 for my NUL folder.

This was then used in the standard command rmdir /s NUL~1 and finally fixed the problem.

spryce
  • 419
  • 4
  • 5
6

If you have Git for Windows Installed do the following

  1. Open the directory containing the files you want to remove
  2. Left Click and select Git Bash Here
  3. Type rm nul.json at the command prompt and hit ENTER, the file now should be removed.

run Git Bash Here

NOTE: These screenshots show the removal of file nul.topo.json which is another file that I could not removed with a simple delete.

after command execution

Geovani Martinez
  • 189
  • 2
  • 4
1

If you have PowerShell 6.1.0 (Sep 2018) or higher:

https://github.com/PowerShell/PowerShell/releases/tag/v6.1.0

you can do something like this:

Remove-Item -LiteralPath \\?\C:\NUL

Another option is this Go program:

package main
import "os"
func main() {
   os.Remove(`\\?\C:\NUL`)
}
Zombo
  • 1
  • 24
  • 120
  • 163
0

Cygwin, git bash or WSL (for Windows 10)

rm PREFIX/c/path/to/the/file/or/folder/you/want/to/delete

PREFIX="/cygdrive" (Cygwin)

2. PREFIX="" (git bash)

3. PREFIX="/mnt" (WSL)

fjy
  • 1