mv files by size

#!/bin/bash
DIRNAME='dirXXXXX'
to=$(mktemp -p . -d "$DIRNAME")
size=0
for f in *.jpg *.png *.jp2; do
  f_size=$(stat -c %s "$f")
  mv "$f" "$to"
  ((size += f_size))
  if ((size > 20000000)); then
    to=$(mktemp -p . -d "$DIRNAME")
    size=0
  fi
done