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 example would be 00303039 would be a match  and 039330a29 would not   So far this is what I have but I am not sure that it is correct   0-9  1 45     I have also tried    0-9  45      but that does not seem to work either  I am not very familiar with regex so any help would be great  Thanks

User · Answer

The first matches any number of digits within your string (allows other characters too, i.e.: "039330a29"). The second allows only 45 digits (and not less). So just take the better from both:

^\d{1,45}$

where \d is the same like [0-9].

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

0-9  1 45   is correct

User · Answer

A combination of both attempts is probably what you need     0-9  1 45

User · Answer

You are almost there  all you need is start anchor     and end anchor         0-9  1 45      d is short for the character class  0-9   You can use that as     d 1 45     The anchors force the pattern to match entire input  not just a part of it     Your regex  0-9  1 45  looks for 1 to 45 digits  so string like  foo1 also get matched as it contains 1     0-9  1 45  looks for 1 to 45 digits but these digits must be at the beginning of the input  It matches 123 but also 123foo   0-9  1 45   looks for 1 to 45 digits but these digits must be at the end of the input  It matches 123 but also foo123    0-9  1 45   looks for 1 to 45 digits but these digits must be both at the start and at the end of the input  effectively it should be entire input

User · Answer

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

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

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