Regex: whitelist of characters + maxmim length + no dot at the end -

Regex: whitelist of characters + maxmim length + no dot at the end -

i not know why i'm struggling simple regex, :)

i need regex match string:

with allowed characters [a-za-z0-9_.-] that contains 1 48 characters that can have dots, not @ end of string

tried bunch of regexes, there's slips through matching. ended with

^([a-za-z0-9_.-]{1,48})([^.])$

for reason, test$ illustration accepted valid. test$$ isn't.

can help me on right track here?

you can utilize negative lookbehind if supported regex engine:

^[a-za-z0-9_.-]{1,48}(?<!\.)$

demo

if regex engine doesn't back upwards negative lookbehinds, supports negative lookaheads, next work you:

^(?!.*\.$)[a-za-z0-9_.-]{1,48}$

demo

regex dot