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I'm looking for some historic info about the null device. Why was it called /dev/null instead of (for example) /dev/empty?

FreeBSD's manual page states that "A null device appeared in Version 7 AT&T UNIX" but I can't find any reference or hint about why that name was originally chosen.

If it turns out that the name was originally used in a more ancient OS, I'd like to know how the original device worked and why that name was chosen.

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  • /dev/null is one of very few pathnames standardized by POSIX. And even non-Unix-like systems call it that way (probably because Unix did it first).
    – Gilles 'SO- stop being evil'
    Dec 26, 2016 at 22:59
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    @Gilles ok but why? What the history behind this specific name?
    – Giacomo Tesio
    Dec 27, 2016 at 14:42
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    I've removed everything except the core question itself from here in the hope that that makes it clearer as a historical question; if I've interfered with what you wanted it to say please roll it back.
    – Michael Homer
    Dec 30, 2016 at 21:40
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    The FreeBSD manual page is correct but somewhat misleading.  The null device, called /dev/null, was present in Version 6 Unix, in the mid 1970s.  (BTW, /dev/zero was added much later.) Unfortunately, I have no supporting evidence.
    – G-Man Says 'Reinstate Monica'
    Jan 1, 2017 at 23:12
  • "on unix an "always blocking file" could be used to wait for signals." As it turns out, there's a system call that's used to wait for signals - pause().
    – Mark Plotnick
    Jan 5, 2017 at 15:52

2 Answers 2

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null was chosen because it discards any data sent, pretty much like a void place. That's why its also called black hole.

It is a character device, a stream that has no connection to a real space in memory. Fun fact is that you can make your own personalized /dev/null with mknod -m 666 /dev/null c 1 3.

Additionally, it sends EOF if you try to read from it.

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'null' means 'nothing', 'without value', and so on.

'empty' implies a container. For emptiness to exist we need a container.

In computer science in which zero is a value, we need a term for 'nothing'. So we have the 'null pointer' for example which is, functionally, a pointer to nothing.

'/dev/null' is the 'nothing device'. If we want something to disappear into nothingness, we give it to the nothing device.

If we give something to /dev/empty then the 'empty' device is no longer empty but is the container of the thing we sent to it.

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