Island Linux Bits and Bytes of Technology

To generate random numbers with bash use the $RANDOM internal Bash function. Note that $RANDOM should not be used to generate an encryption key. $RANDOM is generated by using your current process ID (PID) and the current time/date as defined by the number of seconds elapsed since 1970. The range of returned values is 0 to 32767.

This will return a number between 1 and 100:

NUMBER=$[ ( $RANDOM % 100 )  + 1 ]

Here is a function to dynamically imitate a die:

#!/bin/bash
#
# Simple script to generate a random number
#
# written by Dallas Vogels

function roll_die() {

  # capture parameter
  declare -i DIE_SIDES=$1

  # check for die sides
  if [ ! $DIE_SIDES -gt 0 ]; then
    # default to 6
    DIE_SIDES=6
  fi
  
  # echo to screen
  echo $[ ( $RANDOM % $DIE_SIDES )  + 1 ]

}

roll_die 10  # returns 1 to 10
roll_die 2   # returns 1 or 2