A Unix shell script to rename many files at one time
By Alvin Alexander. Last updated: November 27 2017
Summary: A Unix/Linux shell script that can be used to rename multiple files (many files) with one shell script command.
Problem
You're on a Mac OS X, Unix, or Linux system, and you'd like to be able to rename a large number of files at once. In particular, you'd like to be able to change the extensions of a large number of files, such as from *.JPG to *.jpg (changing the case of each file extension from upper case to lower case).