How To: convert uppercase to lowercase in a file
There are many scripts available to quickly convert uppercase file names to lowercase but not too many to convert content of a file from uppercase to lowercase or lowercase to uppercase.
Here is how to convert from upper to lowercase:
$ tr '[:upper:]' '[:lower:]' < input_file.txt > output_file.txt
To convert from lowercase to uppercase:
$ tr '[:lower:]' '[:upper:]' < input_file.txt > output_file.txt
Done!