/dev/zero: The psuedo-device that produces an endless stream of NULs

This device should NOT be confused with /dev/null. While reading from /dev/null returns 0 bytes of input (and indicates an EOF), reading from /dev/zero returns an endless stream of ASCII NUL characters (which is the "zero" 0 character in that set). (I'm not sure what it returns on the rare EBCDIC or other non-ASCII UNIX system; presumably still a stream of "zero" bits; whatever character that is to that architecture). (Writing to /dev/zero is undefined in the POSIX spec.? Thus it might succeed as with /dev/null, or it might return an error as if the device was full: EINVAL, EIO, or ENOSPC are possible errors in that case. Linux seems to simply allow writes to /dev/zero without error or complaint.)

See FHS#3_6_dev_Device_files.

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• () JimDennis - 22 Oct 2003
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