No python, no fancy stuff, nothing but plain old bash:
for i in *; do
j=`echo $i | tr '[A-Z]' '[a-z]'`
if [ "$i" != "$j" ]; then
mv $i $j
fi
doneOr on a single line: for i in *; do j=`echo $i | tr '[A-Z]' '[a-z]'`; if [ "$i" != "$j" ]; then mv $i $j; fi; done Phil.

