Question

Can anyone please tell me regular expression so that only ‘a’,’A’,’p’ and ‘P’ can be entered as input and at a time only one of those character should be entered?

Thanks in advance.

Answer 1

Here’s a simple one: [aApP]

Does that work for you?

You might have to add language-specific start & end line symbols, e.g. ^[aApP]$ if you want to check that the entire input consists only of that one character.