Bash: How to generate a random number within given boundaries

$RANDOM on bash returns a random integer between 0 and 32767.

echo $RANDOM
9816
echo $RANDOM
30922

If you want to limit that to a certain maximum, you can just compare against the modulus of that maximum + 1. \
For example, the following will yield results between 0 and 9:

echo $(($RANDOM % 10))
5
echo $(($RANDOM % 10))
9

Note that this skews random numbers to the lower regions of your boundaries in most cases.