/dev/null
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In Unix-like operating systems, /dev/null or the null device is a special file that discards all data written to it but reports that the write operation succeeded. It provides no data to any process that reads from it, yielding EOF immediately.[1]
In programmer jargon, especially Unix jargon, it may also be called the bit bucket[2] or black hole.
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Usage [edit]
The null device is typically used for disposing of unwanted output streams of a process, or as a convenient empty file for input streams. This is usually done by redirection.
The /dev/null device is a special file, not a directory, so one cannot move a whole directory into it with the Unix mv command. The rm command is the proper way to delete files in Unix.
This concept is roughly equivalent to the NUL: or just NUL device of CP/M, DOS and Windows, the \Device\Null of Windows NT and its successors, the NIL: of Amiga operating systems, and the NL: of OpenVMS. In Windows Powershell, the equivalent is $null.
References in computer culture [edit]
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".[3] 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").[citation needed] In 1996, Dev Null was an animated virtual reality character created by Leo Laporte for MSNBC's computer and technology TV series, The Site. A 2002 advertisement for the Titanium PowerBook G4 reads The Titanium Powerbook G4 Sends other UNIX boxes to /dev/null. [4]
The null device is also a favorite subject of technical jokes,[5] 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.
See also [edit]
- /dev
- Filesystem Hierarchy Standard
- Memory hole
- rm (Unix)
- Standard streams
- Unix philosophy
- Write-only memory
References [edit]
- ^ "Single Unix Specification Section 10.1: Directory Structure and Files". The Open Group. Retrieved 2012-11-29.
- ^ Jargon file entry for "bit bucket"
- ^ The Linux Kernel Archives FAQ at kernel.org
- ^ http://www4.macnn.com/macnn/articles/unixad.jpg
- ^ "The FreeBSD Funnies". Freebsd.org. Retrieved 2012-11-28.
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