Using regex to crop the last few digits

Question

Using regex. trying to get only the last x digits of the number and 0 where necessary,

Consider the next entry

1234 123 12 1 

EDIT: they will be displayed individually as string values

I'm trying to make a regex expression (or multiple regex expressions, ideally just one)

 34 23 12 01 

I'm a little new to regex and callback and still staggering a bit. any ideas on where to look or what can be done?

thanks

EDIT To clarify: For use in .net System.Text.Regex.Replace (), any of these values ​​may be included as an input parameter.

EDIT: Thanks to everyone for the ideas. This seems to be impossible to do in regular expression. Sad as it is.

Answer 1

If you must use regular expressions, this can be done if you use MatchEvaluator, but it is better not to use regular expressions for this task.

Since you pointed out that a solution that doesn't use regular expressions might be acceptable, here is one way to do it in C # that doesn't use regular expressions:

 void Run() { string s ="1234"; s = lastXDigits(s, 3); Console.WriteLine(s); } string lastXDigits(string s, int x) { if (s.Length < x) { return s.PadLeft(x, '0'); } else { return s.Substring(s.Length - x); } } 

The result for each of your inputs:

  234
 123
 012
 001

Answer 2

Based on your other questions, I assume that you are using VB.Net.

You do not need a regular expression; you can just use string manipulation:

 Dim str As String If str.Length > 2 Then str = str.Substring(str.Length - 2) str = str.PadLeft(2, '0'c) 

Answer 3

what you can do is use .substring(int start, int length) and then format the string up to two characters long, but if you don't specify the language, our hands are a bit tied.

Answer 4

This will not fill in zero, but it seems to work (tested in JavaScript):

 /[0-9]{1,2}$/ 

Answer 5

What language do you use? .. It could be easier without regular expression.

For example, how can you do this in PHP:

 $arr = array(1234,123,12,1); foreach($arr as $num) { echo '<br />'.str_pad(substr($num,-2), 2, "0", STR_PAD_LEFT); }