(macOS terminal) Replacing multiple dots in filename with underscore

I have thousands of jpg files like

juba.cor.top.jpg
juba.jpg
juga.caaa.wadea.dfda.jpg
juga.caaa.wadea.dfda.jpg
juga.caaa.wadea.dfda.afasfs.jpg
juga.caaa.wadea.dfda.aefaf.afdssaf.afdasfs.jpg

I want to find those files which have multiple dots in the name. In the previous list, I want to match all except juba.jpg and replace these dots with underscores.

I would like to convert the previous list into

juba_cor_top.jpg
juba.jpg
juga_caaa_wadea_dfda.jpg
juga_caaa_wadea_dfda.jpg
juga_caaa_wadea_dfda.afasfs.jpg
juga_caaa_wadea_dfda_aefaf_afdssaf_afdasfs.jpg

I have discovered that the following regex matches the files I want:

find -E . -regex '(.*\..*){2,}\.jpg'

Now, how do I rename them?

>Solution :

Get the part of the name before .jpg, and replace all the . with _ in it.

for file in *.*.jpg
do
    base=${file%.*} # remove jpg suffix
    base=${base//./_} # replace all . with _
    mv "$file" "$base.jpg"
done