Regex to match numbers starting with 1, maximum 12 digits

Question

I am searching for a regular expression that matches any string that is:

1. A number which is greater than zero
2. The number has at least one digit
3. No more than 12 digits

I tried this one without success:

^[1-9][0-9]*{1,12}$

Answer 1

If numbers with leading zeros that are greater than zero are allowed, you can use ^(?!0+$)[0-9]{1,12}$ if the tool/language you use supports lookaheads. The lookahead is used to ensure that the number doesn't entirely consist of zeros.

Answer 2

^[1-9][0-9]{0,11}$

Start with a single digit between 1-9, then have 0 to 11 occurrences of a digit between 0-9