Regular Expression Help!

[Goksly]

Hello all!
I have to produce a regular expression whichs validates a password against the following:

• 8 to 12 character long
• Can’t start with a digit
• No more then two consecutive characters can be identical.
• Alpha Numeric only.

My best attempt is:
(\b(?=\w{8,12}\b)(?=(\w)(?!=\1\1))[a-zA-Z]\w*

but it doesnt work in all situations... the real problem is the two consecutive chars... Is there a way to make a look ahead only apply to the result from a previous look ahead - or does that just give (internally) a true or false and either proceeds or skips?
Thanks in advance

 

[Dj_Jestar]

The consecutive one will be tricky, at least would be for me with my knowledge of regex

The others can be done in multiple regex's though.

8 to 12:

^.{8,12}$

no digit start:

^[a-zA-Z]+.+$

alpha-num only:

^[a-zA-Z0-9]+$

Or in one (untested and without the consecutive checking):

^([a-zA-Z]+?([a-zA-Z0-9]+)){8,12}$

 

[Goksly]

Yeah its the consecutive one thats the problem... done the others pretty easy. The problem is with words like "ggeeeeeee"; the expression looks at g, checks the next two chars.... one is an 'e' so it passes the look ahead. Need a way to look at each character, check infront of it two places and if there are any repetitions for each of the checked chars the whole regex should fail.

As it is, if there is one pass, the whole thing passes.

 

[paulsheff]

I'm a bit confused, why does it need to look 2 characters ahead?

ggeeeeee is not valid but say gegegege you would want to be?

 

[paulsheff]

Ahh right sorry just got what you meant.