Shell Scripting: Convert Uppercase to Lowercase

Source:
http://www.cyberciti.biz/faq/linux-unix-shell-programming-converting-lowercase-uppercase/

Q. How do I convert uppercase words to lowercase or vise versa under BASH shell? I've a small shell script and I'd like to convert all incoming user input to lowercase using a shell script.



A. Use tr command to convert all incoming text / words / variable data from upper to lower case or vise versa (translate all uppercase characters to lowercase).

Convert all text file data from upper to lowercase:
Type the following command at shell:

$ tr '[:upper:]' '[:lower:]' <> output.txt

Convert variable data from upper to lowercase:
$ echo $VAR_NAME tr '[:upper:]' '[:lower:]'
$ echo $VAR_NAME tr '[:lower:]' '[:upper:]'