regex - Limit length of characters in a regular expression?

Question

Is there a way to limit a regular expression to 100 characters WITH a regular expression?

[size=(.*?)](.*?)[/size]

So Look at me! wouldn't work.

I want to limit the numbers, only allow numbers between 1 and 100.

Answer 1

Is there a way to limit a regex to 100 characters WITH regex?

Your example suggests that you'd like to grab a number from inside the regex and then use this number to place a maximum length on another part that is matched later in the regex. This usually isn't possible in a single pass. Your best bet is to have two separate regular expressions:

• one to match the maximum length you'd like to use
• one which uses the previously extracted value to verify that its own match does not exceed the specified length

If you just want to limit the number of characters matched by an expression, most regular expressions support bounds by using braces. For instance,

d{3}-d{3}-d{4}

will match (US) phone numbers: exactly three digits, then a hyphen, then exactly three digits, then another hyphen, then exactly four digits.

Likewise, you can set upper or lower limits:

d{5,10}

means "at least 5, but not more than 10 digits".

---

Update: The OP clarified that he's trying to limit the value, not the length. My new answer is don't use regular expressions for that. Extract the value, then compare it against the maximum you extracted from the size parameter. It's much less error-prone.