At times we have files that might contain Uppercase letters that need to be renamed to lowercase. The following script can help in this case. 

Lowercase Script

Windows

for /F %a in ('dir /L /B') do ren %a %a

Mac/Linux

for f in *; do mv "$f" "$f.tmp"; mv "$f.tmp" "`echo $f | tr "[:upper:]" "[:lower:]"`"; done