regex - Regular Expression for Password

Question

I need help creating a password regex. A password must contain at least 4 characters, letters (uppercase and lowercase), numbers and special characters - no spaces.

msn like regular expression.

Answer 1

This regex works - see test data and output below:

^(?=.{4,})(?=.*d)(?=.*[a-z])(?=.*[A-Z])(?!.* )(?=.*[@#$%^&+=i.,!?:;*/])

Test data in passwords.txt (only the first should pass):

aB#1
aB #1
ab#1
AB#1
aB#a
aB1a
aB1

mac-osx> grep -P '^(?=.{4,})(?=.*d)(?=.*[a-z])(?=.*[A-Z])(?!.* )(?=.*[@#$%^&+=i.,!?:;*/])' passwords.txt
aB#1

You can add whatever extra "special characters" you need into the last look ahead regex's character class.