Remove file extension in OS X using Terminal
Solution 1:
If these files are all in the same directory you can rename them like this:
for f in /some/dir/*.JPG.jpg; do
mv "$f" "${f%.*}"
done
${f%.*} removes shortest text matching the pattern .* (a dot followed by arbitrary text) from the end of the variable $f (in this case the file name), thus producing commands like the following:
mv "/some/dir/DSC01852.JPG.jpg" "/some/dir/DSC01852.JPG"