RegEx to make sure that the string contains at least one lower case char, upper case char, digit and symbol

Question

What is the regex to make sure that a given string contains at least one character from each of the following categories.

• Lowercase character
• Uppercase character
• Digit
• Symbol

I know the patterns for individual sets namely [a-z], [A-Z], \d and _|[^\w] (I got them correct, didn't I?).

But how do I combine them to make sure that the string contains all of these in any order?

Answer 1

You can match those three groups separately, and make sure that they all present. Also, [^\w] seems a bit too broad, but if that's what you want you might want to replace it with \W.

Answer 2

If you need one single regex, try:

^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*(_|[^\w])).+$

A short explanation:

^                  // the start of the string
(?=.*[a-z])        // use positive look ahead to see if at least one lower case letter exists
(?=.*[A-Z])        // use positive look ahead to see if at least one upper case letter exists
(?=.*\d)           // use positive look ahead to see if at least one digit exists
(?=.*[_\W])        // use positive look ahead to see if at least one underscore or non-word character exists
.+                 // gobble up the entire string
$                  // the end of the string

And I agree with SilentGhost, [^\w] might be a bit broad. I'd replace it with a character set like this: [-+_!@#$%^&*.,?] (feel free to add more of course!)