I take a few minutes to explain a quick mass renaming shortcut using sed I use when I have multiple files that I need to rename. I used the example of spaces in filenames, but you can use this to append a name to multiple files.
Another way to easily change files is to use the 'tr' command. You can change a filename from all lowercase to all uppercase letters, or even remove non-printable characters from filenames.
Take a look, please leave feedback. I know there are other ways using awk, perl, and others. This is just another way to do it.
