Regex to allow alpha numeric but not just numeric with minimum 6 characters and max 100

Question

Minimum characters required 6 and maximum characters 100.

All numeric is not allowed -111111 Alpha numeric is allowed - abc123 Special characters is allowed -_@! Only letters is allowed- abcdefgh

AAAAAA =>OK
111111=> NOT OK
AAA123!=>OK
AAA12 => NOT ok minimum 6 characters 
11111_ =>OK

I tried with this regex ^[a-zA-Z][a-zA-Z0-9]*$..it works but i cannot get the minimum 6 or max 100 in this.

^[a-zA-Z][a-zA-Z0-9]*$

All numeric is not allowed -111111 Alpha numeric is allowed - abc123 Special characters is allowed -_@! Only letters is allowed- abcdefgh

underspecified. is 12343a allowed? is @12345 allowed - what about 12345@ - why regex? — Patrick Artner
– Patrick Artner, Commented Jun 3, 2019 at 19:46
"[^0-9]" for the regexp and .Length >= 6 to check the length? — sticky bit
– sticky bit, Commented Jun 3, 2019 at 19:51
i could check .length but i want everything to be in a regex — user4379225
– user4379225, Commented Jun 3, 2019 at 20:09

The fourth bird · Accepted Answer · 2019-06-03 20:07:18Z

1

Your pattern starts with matching [a-zA-Z]. If it is not required that a-zA-Z should be at the start but only at least 1 times in the whole match, if supported, you could use a positive lookahead to assert the length of 6 - 100.

Then you could make sure to match at least 1 time a-z or A-Z or a special chacter between matching 0+ times [a-zA-Z0-9_@!-]* on the left and on the right:

^(?=.{6,100}$)[a-zA-Z0-9_@!-]*[a-zA-Z_@!-][a-zA-Z0-9_@!-]*$

^ Start of string
(?=.{6,100}$) Assert what is on the right is 6 - 100 characters except a newline
[a-zA-Z0-9_@!-]* Match 0+ times what is listed in the character class
[a-zA-Z_@!-] Match a character a-z or A-Z or a special char without a digit
[a-zA-Z0-9_@!-]*Match 0+ times what is listed in the character class
$ Assert end of the string

Regex demo

Another option is to a positive and a negative lookahead, 1 to check for the length and the other (?!\d+$) to check if the match does not consists of only digits:

^(?=.{6,100}$)(?!\d+$)[a-zA-Z0-9_@!-]+$

Regex demo

edited Jun 3, 2019 at 20:07

answered Jun 3, 2019 at 19:56

The fourth bird

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2 Comments

user4379225 Over a year ago

this doesnt allow 11111_ =>OK

The fourth bird Over a year ago

@user4379225 Do you mean like this? regex101.com/r/q1JLmc/2 I have updated the answer.

Oflocet · Accepted Answer · 2019-06-03 19:54:13Z

0

You can define a range to help with your length requirements.

^[a-zA-Z][\w\d!_\-@]{5,99}$

The first character being mandatory and the remaining symbols being of length 5 to 99.

As commented by Mr. Artner, you could elaborate on your need so we could provide a better answer.

answered Jun 3, 2019 at 19:54

Oflocet

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