Escaping square bracket in bash inside a string for an if

Question

I'm trying to do a simple if statement but one of the string contains square brackets.

I've tried with \ ' " + and everything came in my mind.

I've basically this:

if [ $MESSAGE = "username [$USERNAME] is already taken" ]

and in this case I would like to throw an error message.

Answer 1

Quote $MESSAGE as well. If that variable does contain a [, it will affect the parsing.

if [ "$MESSAGE" = "username [$USERNAME] is already taken" ]