大写转小写：
for fname in *; do mv $fname `echo $fname|tr [A-Z] [a-z]`; done小写转大写：
for cpplive in *; do mv $cpplive `echo $cpplive|tr [a-z] [A-Z]`; done大写转小写：
for cpplive in *; do mv $cpplive `echo $cpplive|tr [A-Z] [a-z]`; done修改后缀：
for cpplive in *.JPG; do mv $cpplive ${cpplive%%\.*}.jpg; done