how to match a number which is less than or equal to 100?

Question

I want to match a number which is less than or equal to 100, it can be anything within 0-100, but the regex should not match for a number which is greater than 100 like 120, 130, 150, 999, etc.

Answer 1

Try this

\b(0*(?:[1-9][0-9]?|100))\b 

Explanation

" \b                # Assert position at a word boundary (                 # Match the regular expression below and capture its match into backreference number 1    0              # Match the character “0” literally       *           # Between zero and unlimited times, as many times as possible, giving back as needed (greedy)    (?:            # Match the regular expression below                   # Match either the regular expression below (attempting the next alternative only if this one fails)          [1-9]    # Match a single character in the range between “1” and “9”          [0-9]    # Match a single character in the range between “0” and “9”             ?     # Between zero and one times, as many times as possible, giving back as needed (greedy)       |           # Or match regular expression number 2 below (the entire group fails if this one fails to match)          100      # Match the characters “100” literally    ) ) \b                # Assert position at a word boundary " 

Answer 2

How about this for the regex:

^([0-9]|[1-9][0-9]|100)$ 

this would validate 7, 82, 100 for examples, but would not validate 07 or 082.

Check this out for more information (and variations including zero prefixing) on number range checking

---

If you need to cater for floating point numbers you should read this, here is an expression you can use:

Floating point: ^[-+]?([0-9]|[1-9][0-9]|100)*\.?[0-9]+$