In Unix-like operating systems, /dev/null or the null device is a virtual device that discards all data written to it, and provides no data to any process that reads from it. In Unix programmer jargon, it may also be called the bit bucket or black hole.

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.

This entity is a common inspiration for technical jargon expressions and metaphors by Unix programmers, e.g. "please send complaints to /dev/null" or "my mail got archived in /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 Fools, 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 flicker on an internal glowing LED.

The (roughly) equivalent DOS device is NUL. Under classic Amiga operating systems, the device's name is NIL:.

See also

• Unix philosophy
• standard streams
• /dev/zero
• /dev/random