null (4) - Linux Man Pages
null: data sink
null, zero - data sink
DESCRIPTIONData written to the /dev/null and /dev/zero special files is discarded.
Reads from /dev/null always return end of file (i.e., read(2) returns 0), whereas reads from /dev/zero always return bytes containing zero ('\0' characters).
These devices are typically created by:
NOTESIf these devices are not writable and readable for all users, many programs will act strangely.
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