die () {
  echo "$1" 1>&2
  exit 1
}

readlink_f () {
  # https://stackoverflow.com/a/1116890
  TARGET_FILE=$1

  cd "$(dirname $TARGET_FILE)"
  TARGET_FILE="$(basename $TARGET_FILE)"

  # Iterate down a (possible) chain of symlinks
  while [ -L "$TARGET_FILE" ]
  do
      TARGET_FILE="$(readlink $TARGET_FILE)"
      cd "$(dirname $TARGET_FILE)"
      TARGET_FILE="$(basename $TARGET_FILE)"
  done

  # Compute the canonicalized name by finding the physical path
  # for the directory we're in and appending the target file.
  PHYS_DIR="$(pwd -P)"
  RESULT="$PHYS_DIR/$TARGET_FILE"
  echo "$RESULT"
}