Tab auto-completion case-insensitive in the terminal

Open a terminal and type the below command:

echo set completion-ignore-case on | sudo tee -a /etc/inputrc

Enter password. Restart terminal.

If in some case you want to remove case insensitive, just edit /etc/inputrc file by 

removing the set completion-ignore-case line.

That's all.

[refer to askubuntu.com]