Regex allow a string to only contain numbers 0 - 9 and limit length to 45

Question

I am trying to create a regex to have a string only contain 0-9 as the characters and it must be at least 1 char in length and no more than 45. so

Answer 1

Rails doesnt like the using of ^ and $ for some security reasons , probably its better to use \A and \z to set the beginning and the end of the string

Answer 2

A combination of both attempts is probably what you need:

^[0-9]{1,45}$

Answer 3

codaddict has provided the right answer. As for what you've tried, I'll explain why they don't make the cut:

• [0-9]{1,45} is almost there, however it matches a 1-to-45-digit string even if it occurs within another longer string containing other characters. Hence you need ^ and $ to restrict it to an exact match.

• ^[0-9]{45}*$ matches an exactly-45-digit string, repeated 0 or any number of times (*). That means the length of the string can only be 0 or a multiple of 45 (90, 135, 180...).

Answer 4

^[0-9]{1,45}$ is correct.

Answer 5

For this case word boundary (\b) can also be used instead of start anchor (^) and end anchor ($):

\b\d{1,45}\b

\b is a position between \w and \W (non-word char), or at the beginning or end of a string.

Answer 6

Use this regular expression if you don't want to start with zero:

^[1-9]([0-9]{1,45}$)

If you don't mind starting with zero, use:

^[0-9]{1,45}$