null man page

null, zero — data sink

Description

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

Files

/dev/null
/dev/zero

Notes

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.)

See Also

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

Colophon

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Referenced By

dmsetup(8), full(4), gsisshd_config(5), sshd_config(5).

zero(4) is an alias of null(4).

2015-07-23 Linux Linux Programmer's Manual