
Null device

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 codice_1 on Unix and Unix-like systems, codice_2 (see TOPS-20) or codice_3 on CP/M and DOS (internally codice_4), codice_5 on newer Windows systems (internally codice_6 on Windows NT), codice_7 on Amiga operating systems, and codice_8 on OpenVMS. In Windows Powershell, the equivalent is codice_9. 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 codice_10.
In programmer jargon, especially Unix jargon, it may also be called the bit bucket or black hole.
History.
According to the Berkeley UNIX man page, Version 4 Unix, which AT&T released in 1973, included a null device.
Usage.
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 codice_1 device is a special file, not a directory, so one cannot move a whole file or directory into it with the Unix codice_12 command.
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 codice_1", "my mail got archived in codice_1", and "redirect to codice_1"—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 codice_1", 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 . 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 codice_1 is already 98% full. The April Fool's, 1995 issue of the German magazine "c't" reported on an enhanced codice_1 chip that would efficiently dispose of the incoming data by converting it to a flicker on an internal glowing LED.