Manpages - null.4

null, zero - data sink

Data 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:

  mknod -m 666 /dev/null c 1 3
  mknod -m 666 /dev/zero c 1 5
  chown root:root /dev/null /dev/zero

/dev/null
/dev/zero

If these devices are not writable and readable for all users, many programs will act strangely.

Since Linux 2.6.31, reads from /dev/zero are interruptible by signals. (This change was made to help with bad latencies for large reads from /dev/zero.)

*chown*(1), *mknod*(1), *full*(4)

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