Get the absolute path of the current script, even when sourced from another script.

psd.sh

##
 # Gets the present source directory (PSD) for the current script. Works when
 # the script is executed directly or when it is being sourced from another
 # script.
 #
 # @switch -P display the physical present source directory (all symbolic links resolved)
 # @switch -L display the logical present source directory
 #
 # @stdout the absolute path to the script invoking the function
 #
 # @exit 0 on success
 #
psd() {
  local HERE="$( [ -z "${BASH_SOURCE[0]}" ] && echo "$0" || echo "${BASH_SOURCE[0]}" )"
  local DIR="$( dirname $HERE )"
  local PSD="$( cd "$DIR" && pwd $@ )"

  # Compact version:
  # ROOT="$( cd $( dirname "$( [ -z "${BASH_SOURCE[0]}" ] && echo "$0" || echo "${BASH_SOURCE[0]}" )" ) && pwd $@ )"

  echo "$PSD"
}