Regex to match 0 - 999 but not blank -

I am working on a valid regex for valid integer numbers like the following:

• 999

However, it should not be allowed to match empty string. The closest I can find is:

  (0) | \\ d {1,3}  

Who says to me that a match string will be either a zero or a series of digits between 1 or 3 characters, however, the still string is still Matches this method. What is the proper way to exclude the empty string from this reggae?

This (only) one to three numerical digits (including 0 or 00 or 01 or 012) Is not that if the latter are):

  ^ \ d {1,3} $  

this will not match empty string (but then your Original compressed expression will not be).

(To allow this as part of a larger string, an code ^ and $ ).

But maybe again RegX is not the best option - the number which is the original language you are using is not a numerical function? 0 to allow 0 but no other 0-prefix numbers, you can use it:

  0 | [1- 9] \ d {0, 2}  

Or, to ensure that the whole match is:

  ^ (?: 0 | [1- 9] \ d {0,2}) $