CODEWITHSUNDEEP
c#regex
sanchop22
sanchop22

Reputation: 2809

Regex statement for only numbers between 0 and 255 in C#

How do i write regex statement for only numbers between 0 and 255? 0 and 255 will be valid for the statement.

Upvotes: 1

Views: 13062

Answers (4)

Cylian
Cylian

Reputation: 11182

Try a negative look behind:

(?<!\-)\b0*([0-9]{1,2}|1[0-9]{2}|2[0-4][0-9]|25[0-5])\b

Explanation

<!--
(?<!\-)\b0*([0-9]{1,2}|1[0-9]{2}|2[0-4][0-9]|25[0-5])\b

Options: ^ and $ match at line breaks

Assert that it is impossible to match the regex below with the match ending at this position (negative lookbehind) «(?<!\-)»
   Match the character “-” literally «\-»
Assert position at a word boundary «\b»
Match the character “0” literally «0*»
   Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «*»
Match the regular expression below and capture its match into backreference number 1 «([0-9]{1,2}|1[0-9]{2}|2[0-4][0-9]|25[0-5])»
   Match either the regular expression below (attempting the next alternative only if this one fails) «[0-9]{1,2}»
      Match a single character in the range between “0” and “9” «[0-9]{1,2}»
         Between one and 2 times, as many times as possible, giving back as needed (greedy) «{1,2}»
   Or match regular expression number 2 below (attempting the next alternative only if this one fails) «1[0-9]{2}»
      Match the character “1” literally «1»
      Match a single character in the range between “0” and “9” «[0-9]{2}»
         Exactly 2 times «{2}»
   Or match regular expression number 3 below (attempting the next alternative only if this one fails) «2[0-4][0-9]»
      Match the character “2” literally «2»
      Match a single character in the range between “0” and “4” «[0-4]»
      Match a single character in the range between “0” and “9” «[0-9]»
   Or match regular expression number 4 below (the entire group fails if this one fails to match) «25[0-5]»
      Match the characters “25” literally «25»
      Match a single character in the range between “0” and “5” «[0-5]»
Assert position at a word boundary «\b»
-->

Upvotes: 1

bitoshi.n
bitoshi.n

Reputation: 2318

Try

([01]?\d\d?|2[0-4]\d|25[0-5])

Upvotes: 0

MichelZ
MichelZ

Reputation: 4394

You can find some numeric ranges here:

http://www.regular-expressions.info/numericranges.html

Your example would be:

^([01]?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])$

Upvotes: 10

Joey
Joey

Reputation: 354724

^([0-9]{1,2}|1[0-9]{2}|2[0-4][0-9]|25[0-5])$

This tool is quite helpful for such things. A little searching doesn't hurt anyone either.

If you want to allow leading zeroes the pattern needs to be adapted, though. E.g.:

^([01][0-9][0-9]|2[0-4][0-9]|25[0-5])$

Upvotes: 4

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