Regular expression: Should not start with 5 digits (or more) in a row

Question

I need to generate a regular expression to validate that the string does not start with 5 digits.

NOT VALID: 12345testing123asd

VALID: 1234testing1234
testing12345
testing

I tried to get the first five chars ^.{0,5} but I do not know hot to add the restriction of \D to those first 5 chars

Also, I tried with this [^0-9][^0-9][^0-9][^0-9][^0-9] but I do not know how to do to include the strings that starts with 4 or less numbers

Could you please help me with this? I am a rookie :(

Just `^(?!\d{5}).+$` possibly. Or maybe `^\d{0,4}\D.*$` does the job too. — JvdV, Sep 27 '21 at 13:19
Hi @WiktorStribiżew, not it is not, because starts with 5 digits (or more) You are right. I will edit the question — IamARookie, Sep 27 '21 at 13:24

score 0 · Accepted Answer · answered Sep 27 '21 at 13:24

If your RegExp flavor of choice supports negative lookaheads, this pattern will match if the string is valid (does not start with 5 or more consecutive digits):

^(?!\d{5,})

^Regex101

Matches:

1234testing1234
testing12345
testing

Does not match:

12345testing123asd

Regular expression: Should not start with 5 digits (or more) in a row

1 Answers1