Random

random.sh

#!/bin/bash
# random
# Creates random strings based on urandom.

usage() {
  echo "$(basename $0)"
  echo '  Returns random strings based on the subcommand.'
  echo '  The seed subcommand defauls to length 40; all others are 20.'
  echo "Usage: $(basename $0) (seed|number|name|word) [-l | --length] <length>"
}

# Subcommand.
case "$1" in
  seed)
    re='[[:graph:]]'
    length=40
    shift
    ;;
  number)
    re='0-9'
    numeric=true
    shift
    ;;
  name)
    re='a-z0-9'
    shift
    ;;
  word)
    re='a-z'
    shift
    ;;
  *)
    usage
    exit 2
    ;;
esac

# Optional args.
args=$(getopt -o l: -l "length:" -n "$(basename $0)" -- "$@")
if [[ $? -ne 0 ]]; then
  echo "$(basename $0): invalid argument" >&2
  exit 2
fi
eval set -- "${args[@]}"
while true; do
  case "$1" in
    -l|--length)
      length=$2
      shift 2
      ;;
    --)
      shift 1
      break
      ;;
    *)
      usage
      exit 2
      ;;
  esac
done

# Defaults.
if [[ -z $length ]]; then
  length=20
fi
if [[ -z $numeric ]]; then
  numeric=false
fi

if $numeric; then
  rand=$(< /dev/urandom tr -dc "$re" | fold -w $length | head -1)
else
  prefix=$(< /dev/urandom tr -dc 'a-z' | fold -w 1 | head -1)
  suffix=$(< /dev/urandom tr -dc "$re" | fold -w $(( length - 1)) | head -1)
  rand="$prefix$suffix"
fi

echo "$rand"
if [[ $(uname) == 'CYGWIN'* ]]; then
  putclip <<< "$rand"
fi