Null device

For the electropop band, see Null Device.
Not to be confused with /dev/zero.

In some operating systems, the null device is a device file that discards all data written to it but reports that the write operation succeeded. This device is called /dev/null on Unix and Unix-like systems, NUL: (see TOPS-20) or NUL on CP/M and DOS (internally \DEV\NUL), nul on OS/2 and newer Windows systems[1] (internally \Device\Null on Windows NT), NIL: on Amiga operating systems,[2] and NL: on OpenVMS.[3] In Windows Powershell, the equivalent is $null.[4] It provides no data to any process that reads from it, yielding EOF immediately.[5] In IBM operating systems DOS/360 and successors[a] and also in OS/360 and successors[b] such files would be assigned in JCL to DD DUMMY.

In programmer jargon, especially Unix jargon, it may also be called the bit bucket[6] or black hole.

  1. ^ "Redirecting Error Messages from Command Prompt: STDERR/STDOUT". support.microsoft.com. Retrieved 2020-03-06.
  2. ^ Commodore-Amiga, Inc. (1986). The AmigaDOS Manual. Bantam Books. p. 12. ISBN 0-553-34294-0.
  3. ^ "OpenVMS Programming Concepts Manual". h30266.www3.hpe.com. Archived from the original on 2020-07-02. Retrieved 2020-03-06.
  4. ^ SteveL-MSFT. "about_Automatic_Variables - PowerShell". docs.microsoft.com. Retrieved 2020-03-06.
  5. ^ "Single Unix Specification Section 10.1: Directory Structure and Files". The Open Group. Retrieved 2012-11-29.
  6. ^ "bit bucket". Jargon File. Retrieved 2013-12-27.


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