Editor's Note: This article has been updated by its author. Thank you, Pat. Have you ever wanted to change the names of many files at once? Or, have you ever needed to use a default value for a ...

Learning this one feature means covering a huge chunk of Bash's capabilities.

protect a variable name from surrounding characters. $ export foo=foo $ echo ${foo}bar # foo exists so this works as expected foobar $ echo $foobar # foobar doesn't ...