rand_gen

#!/bin/bash

# demo for the random generator in BASH
# the other function requires 'shuf' utility to be installed

# pure BASH version
random_gen() {
  LIMIT=${1:-100}     # function can accept LIMIT as $1
  declare -ia r_num   # declare array of integers
  local i=1
  until ((i>LIMIT)); do
    num=$RANDOM            # RANDOM returns a random number every time
    for j in ${!r_num[@]}; do 
      if (($num==${r_num[$j]})); then  # check that it is unique
        continue 2
      fi
    done
    ((i++))
    r_num+=($num)    # add a new unique number to array
  done
  declare -p r_num   # dirty print out
}
time random_gen           # calling the function


# The other version of making the same array of random numbers:
# Just a reminder, that BASH is about getting to work 
# all sort of utilities together
random_gen_shuf() {
  declare -ia r_num=($(shuf -i1-${1:-100} -n${1:-100}))
  declare -p r_num
}

time random_gen_shuf