Generate a Safari-style password in bash

safari-style-password.sh

#!/bin/bash

# ################################################
#
# Generate a Safari-style password: V4R-cG2-Cru-J5d
#
# Usage:
# $ MY_PASSWORD=$(./safari-style-password.sh)
# $ echo $MY_PASSWORD
#
# ################################################

function getRandomASCIICodeForDigitsAndLetters {
  # ASCII Codes
  # Digits 0-9, range 048 - 057
  # Letters A-Z, range 065 - 090
  # Letters a-z, range 097 - 122
  # :;<=>?@ special chars, range 058 - 064
  #  [\]~_` special chars, range 091 - 096
  # Range of all above: 048 - 122

  local UPPER_LIMIT=122
  local LOWER_LIMIT=48

  # Safari does not use any special characters except for "-"
  local DISALLOWED_CODES=( 58 59 60 61 62 63 64 91 92 93 94 95 96 )

  # NOTE: Double-parenthesis allow for arithmetic evaluation.
  local DIFF=$(($UPPER_LIMIT - $LOWER_LIMIT + 1))
  local RANDOM_DIGIT=$(( $(($RANDOM%$DIFF)) + $LOWER_LIMIT))

  if [[ " ${DISALLOWED_CODES[@]} " =~ " ${RANDOM_DIGIT} " ]]; then
    # Re-roll
    local RANDOM_DIGIT=$(getRandomASCIICodeForDigitsAndLetters)
  fi

  echo $RANDOM_DIGIT
}

function transformASCIICodeToCharacter () {
  printf '%b' $(printf '\\x%x' $1)
}

function generateRandomPassword {
  RANDOM=$(echo $$) # "Seed" RANDOM w/ PID
  local SECURE_PASSWORD="" # Ensure SECURE_PASSWORD starts off as a blank string

  # Add hyphens to the password: XXX-XXX-XXX-XXX
  local HYPHENATE=( 4 8 12 )

  for i in `seq 1 15`;
  do
    RANDOM_DIGIT=-1
    RANDOM_DIGIT=$(getRandomASCIICodeForDigitsAndLetters)
    if [[ " ${HYPHENATE[@]} " =~ " ${i} " ]]; then
      SECURE_PASSWORD="$SECURE_PASSWORD-"
    else
      CHAR=$(transformASCIICodeToCharacter "$RANDOM_DIGIT")
      SECURE_PASSWORD="$SECURE_PASSWORD$CHAR"
    fi
  done

  echo $SECURE_PASSWORD
}

generateRandomPassword