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

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?

regex


Solution 1:[1]

If you need one single regex, try:

(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*\W)

A short explanation:

(?=.*[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 non-word character exists

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!)

Solution 2:[2]

Bart Kiers, your regex has a couple issues. The best way to do that is this:

(.*[a-z].*)       // For lower cases
(.*[A-Z].*)       // For upper cases
(.*\d.*)          // For digits
(.*\W.*)          // For symbols (non-word characters)

In this way you are searching no matter if at the beginning, at the end or at the middle. In your have I have a lot of troubles with complex passwords.

Solution 3:[3]

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.

Solution 4:[4]

Bart Kiers solution is good but it misses rejecting strings having spaces and accepting strings having underscore (_) as a symbol.

Improving on the Bart Kiers solution, here's the regex:

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

A short explanation:

(?=.*[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 non-word character exists
(?=.*_)           // use positive look ahead to see if at least one underscore exists
|           // The Logical OR operator
^[^ ]+$           // Reject the strings having spaces in them.

Side note: You can try test cases on a regex expression here.

Sources

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Source: Stack Overflow

Solution Source
Solution 1
Solution 2 Elijah Mock
Solution 3 SilentGhost
Solution 4 Ensei_Tankado

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