Useful /dev files

These are device nodes which don’t correspond to any physical devices (pseudo-device files)

/dev/null

accepts and discards all input written to it; provides an end-of-file indication when read from.

Usage:

cat ~/some.txt > /dev/null

/dev/zero

accepts and discards all input written to it; produces a continuous stream of null characters (zero-value bytes) as output when read from.

Usage:

dd if=/dev/zero of=dummy.file bs=1024 count=1

hexdump -C dummy.file
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000400

/dev/urandom

/dev/urandom and /dev/random provide an interface to the kernel’s random number generator.

Myths about /dev/urandom

Usage:

head -30 /dev/urandom > ~/random_30.txt

For simpler usecase, like getting a random positive integer, use the shell variable $RANDOM

echo $RANDOM
12685