#!/bin/bash

# generate a random string of length '$bytes' using characters from
# expression '$chars'
generate_random_string() {
  local bytes=${1:-24}
  local chars=${2:-'A-Za-z0-9'}

  dd if=/dev/urandom bs=1 count=1111 2>/dev/null \
    | tr --complement --delete "$chars" \
    | sed --quiet 's/\(.\{'"$bytes"'\}\).*/\1/p'
}

# function generate_random_string is meant to be used in different
# scripts in contexts like:
# generating a random password
echo "password = '$(generate_random_string)'"
# generating a 64 byte seed base64 encoded
echo "seed = '$(generate_random_string 86 'a-zA-Z0-9/+')=='"