Regular Expression to match some strings

Question

I want to find any string from the following set of strings from the user's input:

• Password@123
• Pa$$w0rd@123
• Password#123
• Pa$$w0rd#123
• Password_123
• Pa$$w0rd_123

The digits at the end should be of the min length 3 & max 6. And this is the regex that I wrote:

(Password@(\d{2,6}))|(Pa\$\$w0rd@(\d{2,6}))|(Password#(\d{2,6}))|(Pa\$\$w0rd#(\d{2,6}))|(Password_(\d{2,6}))|(Pa\$\$w0rd_(\d{2,6})).$

I tested my regex on this website and it is not working fine.

It shows "test passed" until the no. of digits reaches 8 (which it shouldn't), and that clearly means that I have made some mistake. I am not an expert in writing Regexes as I am new to this. I don't understand where am I making a mistake.

Answer 1

Your regex should look something like this: ^pa[s5$][s5$]w[o0]rd.\\d{3,6}$ I'm not 100% sure on the C# exact syntax though. I've set up a test suite at regex101 to show you how it works.

This will grab any combination of the string you've given along with 3-6 digits at the end.

https://regex101.com/r/1KaJNz/2

Answer 2

I would recommend using character sets to simplify your regex. This way you don't have to repeat the common logic for every permutation, which, of course is the point of a regex in the first place. With that, I came up with the following:

Pa[s\$]{2}w[o0]rd[@#_]\d{3,6}

You can also add a 5 into the first character set if you want to allow that, as suggested by @JustinMacArthur.

The problem with the regex given in your answer may have something to do with the . at the end which matches any character. This would let any character come after the numbers (including another number) and it would still match.

Answer 3

You can try this regex. Testing of it looks good:

Pa(\$|s){2}w(0|o)rd[@#_]\d{3,6}