linux/.config/bash/module/checksum.sh

# Save file checksums.
checksum_create()
{
  local file=".checksum"

  # Error if checksum already exists.
  if [[ -f "${file}" ]]; then
    echo -e "${color_bred}Checksum already exists.${color_default}"
    return 1
  fi

  find -type f | parallel -j $(_core_count) -- sha1sum {} >> "${file}"
  sed -i "/${file}/d" ${file}
}

# Check stored values against actual files.
checksum_check()
{
  local file=".checksum"
  local failed=0

  cat "${file}" | parallel -j $(_core_count) -- _checksum_check {} || ((failed++))

  if [[ ${failed} = 0 ]]; then
    echo -e "${color_green}All successful.${color_default}"
    return 0
  else
    # echo -e "${color_bred}Items failed to validate: ${failed}.${color_default}"
    return 1
  fi
}

# Check old values and create new one if all was fine.
checksum_update()
{
  local file=".checksum"

  if [[ ! -f "${file}" ]]; then
    echo -e "${color_bred}Checksum doesn't exists.${color_default}"
    return 1
  fi

  checksum_check && rm "${file}" && checksum_create
}

_checksum_check()
{
  local file="${1##*\ \ }"
  local stored="${1%%\ \ *}"
  local failed=0

  # Skip if no file.
  [[ -f "${file}" ]] || return 0

  # Check file hash.
  local actual=$(sha1sum "${file}")
  actual="${actual%%\ \ *}"

  # Compare values.
  if [[ "${stored}" != "${actual}" ]]; then
    echo -e "${color_bred}${file}: Failed.${color_default}"
    return 1
  fi

  return 0
}

export -f _checksum_check