After a long, unsuccessful search I am starting to wonder if what I am looking for is possible, I would like a regular expression which requires that each letter chosen is mandatory but only once and in any order.
Example : ^[abc]{3}$
The result I expect would be that it matches only that :
abc, bac, cba, acb
While I get :
acc, abb, cca, aab
Do you see where I am going with this?
>Solution :
You may use a regex like this with a negative lookahead of the matched character in a back-reference:
^(?:([abc])(?!.*\1)){3}$