Editing Virtual device (section)

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A '''virtual device''' in [[Unix]] is a file such as <code>[[:/dev/null]]</code> or <code>[[:/dev/urandom]]</code>, that is treated as a device, as far as user level software is concerned, but is generated by the [[kernel (operating system)|kernel]] without reference to hardware.

For instance when <code>/dev/null</code> is written to, the kernel tells the program it wrote everything to it (without actually writing it anywhere), and when read from, the reading program is told that it has reached the end of the file.  It is a device file (it can be made with [[mknod]] for instance), but does not reference any hardware.

[[DOS]]-, [[Microsoft Windows|Windows]]- and [[OS/2]]-like [[operating system]]s define the '''NUL''' device that performs a similar function (but is implemented as part of the file name processing &ndash; no actual file exists by that name).

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[[Category:Unix file system technology]]


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