Found this cool little thing today when I was looking for a way to create a random number in BASH. It seems that BASH does the hard work for you and creates a variable called $RANDOM
# echo $RANDOM 26031 # echo $RANDOM 20163 # echo $RANDOM 30045
And if you want to print off a certain range such as 0 - 100 you can do it like so.
# echo $((RANDOM%100)) 81
Figured I would share this as it is a cool little trick.