Simple password generator, version 2

pw

#!/usr/bin/env sh

set -eur

generate()
{
  allowed_characters="${1}"
  number_of_characters="${2}"
  cat /dev/random | env LC_CTYPE=C tr -cd "${allowed_characters}" | head -c "${number_of_characters}"
}

get_line()
{
  line_number="${1}"
  file_name="${2}"
  awk '/'${line_number}'/{ print NR; exit }' "${file_name}"
}

get_word()
{
  text_line="${1}"
  file_name="${2}"
  awk 'NR=='${text_line}'' ${file_name}
}

echored()
{
  (>&2 echo "\033[1;31m${1}\033[0m")
}

echoyellow()
{
  echo "\033[1;33m${1}\033[0m"
}

echogreen()
{
  echo "\033[1;32m${1}\033[0m"
}

usage ()
{
  echogreen "Usage: pw [options] length"
  echo "Generates a random password with the given limitations, and copies to the clipboard"
  echo "\t-n\tNumeric character limitation"
  echo "\t-a\tAlphabetic character limitation"
  echo "\t-l\tLowercase character limitation"
  echo "\t-d\tDiceware passphrase (exclusive to other options)"
  echo "\t-p\tPrint password or passphrase instead of copying to clipboard"
  echo ""
  exit 1
}

numeric_characters=0
alpha_characters=0
lowercase_characters=0
diceware=0
print_output=0
length=""

numeric_regex="^[0-9]+$"

# parse arguments
while [ $# -gt 0 ]
do
  case "${1}" in
    "-h"|"--help")
      usage
      shift
      ;;
    "-n"|"--numeric")
      numeric_characters=1
      shift
      ;;
    "-a"|"--alpha")
      alpha_characters=1
      shift
      ;;
    "-l"|"--lowercase")
      lowercase_characters=1
      shift
      ;;
    "-d"|"--diceware"|"-w")
      diceware=1
      shift
      ;;
    "-p"|"--print")
      print_output=1
      shift
      ;;
    *) # all other parameters
      if [[ "${length}" == "" && "${1}" =~ ${numeric_regex} ]]; then
        length="${1}"
      else
        echored "Invalid or unexpected argument: ${1}"
        exit 1
      fi
      shift
      ;;
  esac
done

if [ "${length}" == "" ]; then
  echored "Length is required; must be a numeric value"
  exit 1
fi

numeric_regex="^[0-9]+$"

if ! [[ "${length}" =~ ${numeric_regex} ]] ; then
   echored "Given value was not a number"
   exit 1
fi

if [ "${diceware}" == "1" ]; then
  set +u

  if [ -z "${DICEWARE_FILENAME}" ]; then
     echored "Please set DICEWARE_FILENAME to the location of your diceware text file."
     exit 1
   fi

   phrase=""

   for i in `seq 1 ${length}`
   do
     dice_number=`generate '1-6' 5`
     word_line=`get_line "${dice_number}" "${DICEWARE_FILENAME}"`
     whole_word=`get_word "${word_line}" "${DICEWARE_FILENAME}"`
     split_word=(${whole_word// / })
     phrase="${phrase} ${split_word[1]}"
   done

   set -u

   if [ "${print_output}" == "1" ]; then
     echo ${phrase}
   else
     echo ${phrase} | tr -d '\n' | pbcopy
     echogreen "Copied to clipboard"
   fi
else
  allowed_characters=""

  if [ "${numeric_characters}" == "1" ]; then
    allowed_characters="${allowed_characters}0-9"
  fi

  if [ "${alpha_characters}" == "1" ]; then
    if [ "${lowercase_characters}" == "1" ]; then
      allowed_characters="${allowed_characters}a-z"
    else
      allowed_characters="${allowed_characters}A-Za-z"
    fi
  fi

  if [ "${allowed_characters}" == "" ]; then
    allowed_characters='a-zA-Z0-9`~!@#$%^&*()_+-={}[]|;<,>.?/'
  fi

  if [ "${print_output}" == "1" ]; then
    generate "${allowed_characters}" "${length}" | xargs echo
  else
    generate "${allowed_characters}" "${length}" | pbcopy
    echogreen "Copied to clipboard"
  fi
fi