Q. I’m using BASH shell filename tab completion feature to complete file names and other stuff. However default tab-completion in bash case-sensitive. It cannot show me /tmp/Y* or /tmp/Y* files. How do I force filename tab-completion in bash case insensitive?

A. According to bash man page completion-ignore-case set to Off. If set to On, readline performs filename matching and completion in a case-insensitive fashion. Readline has variables that can be used to further customize its behavior. A variable may be set in the /etc/inputrc file with a statement of the form. So all you have to do is type following command:
$ set completion-ignore-case on

You need to add set completion-ignore-case on to /etc/inputrc command:
vi /etc/inputrc
Append text as follows:
set completion-ignore-case on
Close and save the file. For more information read bash man page.