CODEWITHSUNDEEP
regex
Neekoy
Neekoy

Reputation: 2543

Regex to check if input (alphanumeric) contains a number smaller than X

This will probably be easy for regex magicians, however I can't seem to figure out a way with my limited knowledge.

I need a regex that would check if an alphanumeric string contains a number smaller than a number (16539065 in my case).

For example the following should be matched:

alpha16000000beta foo300bar

And the following should not be matched:

foo16539066bar

Help please.

EDIT: I'm aware that it's inefficient, however I'm doing it in a cPanel Account Level filter, which only accepts regex. Unless I figure out a way for it to trigger a script instead, this would definitely need to be done with regex. :(

Upvotes: 0

Views: 101

Answers (2)

Sebastian Proske
Sebastian Proske

Reputation: 8413

Bad Karma might kill me, but here is a working solution for your cases (letters then numbers then letters). It will not work for e.g. ab12cd34de. There is not really a way to shortcode anything, just the long way. I'm using a negative lookahead to check, that the number is not bigger or equal to 16539065.

^\D*(?!0*(?:\d{9}|2\d{7}|1[7-9]\d{6}|16[6-9]\d{5}|165[4-9]\d{4}|16539[1-9]\d{2}|165390[7-9]\d|1653906[5-9]))\d+\D*$

It checks for the general format ^\D*\d+\D*$ and then rolls 16539065 down to it's parts.

Here's a little demo to play around: https://regex101.com/r/aV6yQ9/1

Upvotes: 0

Jenos
Jenos

Reputation: 171

Your best option for this kind of operation is to use a capture group to get the number and then use whatever language you are using to do the comparison. If you absolutely have to use a regex to do this, it will be extremely inefficient. To do so, you will need to combine a lot of similar expressions:

  • \d{1,7} will find any numbers with 1 to 7 digits, which will always be less than 16539065
  • 1653906[1-4] will catch the absolute maximum values accepted
  • 165390[1-5]\d will catch the next range of acceptable values
  • 1653[1-8]\d{3} will continue on the acceptable range
  • Repeat the above until you reach 1[1-5]\d{6}

Once you have all of those expressions, they can be combined using the 'or' operator. Keep in mind that using regular expressions in this manner is considered to be bad practice and creates hard to read code.

Upvotes: 1

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