Bash – How to utilize XDG directories and paths in Bash

I wonder how to access not only the variables defined in ~/.config/user-dirs.dirs with xdg-user-dir, e.g. "$(xdg-user-dir VIDEOS)", but also the following standard variables:

1. XDG_CACHE_HOME:-$HOME/.cache
2. XDG_CONFIG_HOME:-$HOME/.config
3. XDG_DATA_HOME:-$HOME/.local/share
4. XDG_RUNTIME_DIR:-"/run/user/$USER"
5. XDG_CONFIG_DIRS:-/etc/xdg
6. XDG_DATA_DIRS:-/usr/local/share:/usr/share

For that purpose I do the following in my ~/.bash_login file:

# Define standard directories.
declare -gx XDG_CACHE_HOME=~/.cache
declare -gx XDG_CONFIG_HOME=~/.config
declare -gx XDG_DATA_HOME=~/.local/share
declare -gx XDG_RUNTIME_DIR="/run/user/$USER"
declare -gx XDG_CONFIG_DIRS="$(IFS=: path /etc/xdg)"
declare -gx XDG_DATA_DIRS="$(IFS=: path /usr/local/share:/usr/share)"
# Source supplementary directories to export or overwrite existing standard ones.
declare a="$XDG_CONFIG_HOME/user-dirs.dirs"
if [[ -e $a ]]; then
  source "$a"
  declare b=""
  for b in ${!XDG_*}; do
    if [[ $b =~ ^XDG_[_[:alnum:]]+_DIR$ ]]; then
      declare -gx "$b"
    fi
  done
fi

Is there a mechanism to access the above directory and path variables other than the user directory variables defined by the "XDG" directory structure specification?