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 on DOS and CP/M,
nul on newer Windows systems (internally
\Device\Null on Windows NT),
NIL: on Amiga operating systems, and
NL: on OpenVMS. In Windows Powershell, the equivalent is
$null. It provides no data to any process that reads from it, yielding EOF immediately. In IBM DOS/360, OS/360 (MFT, MVT), OS/390 and z/OS operating systems, such files would be assigned in JCL to
|Special device files|
According to the Berkeley UNIX man page, Version 4 Unix, which AT&T released in 1973, included a null device.
References in computer culture
This entity is a common inspiration for technical jargon expressions and metaphors by Unix programmers, e.g. "please send complaints to
/dev/null", "my mail got archived in
/dev/null", and "redirect to
/dev/null"—being jocular ways of saying, respectively: "don't bother sending complaints", "my mail was deleted", and "go away". The iPhone Dev Team commonly uses the phrase "send donations to
/dev/null", meaning they do not accept donations. The fictitious person name "Dave (or Devin) Null" is sometimes similarly used (e.g., "send complaints to Dave Null"). In 1996, Dev Null was an animated virtual reality character created by Leo Laporte for MSNBC's computer and technology TV series The Site. Dev/null is also the name of a vampire hacker in the computer game Vampire: The Masquerade – Redemption. A 2002 advertisement for the Titanium PowerBook G4 reads The Titanium Powerbook G4 Sends other UNIX boxes to /dev/null.
The null device is also a favorite subject of technical jokes, such as warning users that the system's
/dev/null is already 98% full. The April Fool's, 1995 issue of the German magazine c't reported on an enhanced
/dev/null chip that would efficiently dispose of the incoming data by converting it to a flicker on an internal glowing LED.
- "Single Unix Specification Section 10.1: Directory Structure and Files". The Open Group. Retrieved 2012-11-29.
- "bit bucket". Jargon File. Retrieved 2013-12-27.
- "null(4)". The NetBSD Project.
- "sh(1) manual from version 4 Unix".
- "Dev-Team Blog - Donations to /dev/null". 2015-09-07. Retrieved 2018-11-15.
- Goodman, Danny (2004). Spam wars : our last best chance to defeat spammers, scammers, and hackers. New York: SelectBooks. p. 170. ISBN 9781590790632. OCLC 1036874851.
- "Image: unixad.jpg, (1094 × 720 px)". Archived from the original on March 26, 2013. Retrieved 2015-09-02.
- "The FreeBSD Funnies". Freebsd.org. Retrieved 2012-11-28.