First, do a dry run (will not actually rename any files) with the following:
for file in *.mov
do
echo mv "$file" "${file/MP4./}"
done
If it all looks fine, remove the echo
from the third line to actually rename the files.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…