how to make any variable entered lowered case

Question

if I asking for a username I have this in the file

read -p 'enter username: ' username

what can I add to make sure it comes out lowercased?

Answer 1

You can do

username="${username,,}"

to convert every character to lower case.

See https://www.gnu.org/software/bash/manual/bashref.html#Shell-Parameter-Expansion.