CODEWITHSUNDEEP
pythonregex
Pyderman
Pyderman

Reputation: 16189

Regex for range of IPv4 addresses

With an IPv4 address range like 169.254.0.0/16 or 192.168.0.0/16, it is straightforward to construct a regex for each, since once you exactly match the first 6 digits, you're done.

But what about matching any address in a looser reserved range such as

100.64.0.0 –
100.127.255.255

A regex beginning with 100\. won't suffice, because there will be numbers outside of the 100.64 and 100.127 bounds (e.g. 100.65.0.0, 100.127.255.256) that will be erroneously matched. How best to capture a range such as this without having to explicitly define each and every valid subrange within each range? The language is Python.

For reference, a full list of reserved IP addresses and ranges can be found here.

Upvotes: 0

Views: 2044

Answers (2)

Alan Tam
Alan Tam

Reputation: 2057

Use of an IPv4 parsing library is preferred. If you insist in using regular expression,

re.search('^(100\.(6[4-9]|[7-9]\d|1[0-1]\d|12[0-7])(\.(\d|[1-9]\d|1\d\d|2[0-4]\d|25[0-5])){2})$', text)

You can see that I am searching separately for:

  • 64-69 (6[4-9])
  • 70-99 ([7-9]\d)
  • 100-119 (1[0-1]\d)
  • 120-127 (12[0-7])

and

  • 0-9 (\d)
  • 10-99 ([1-9]\d)
  • 100-199 (1\d\d)
  • 200-249 (2[0-4]\d)
  • 250-255 (25[0-5])

Upvotes: 3

Joe T. Boka
Joe T. Boka

Reputation: 6589

This is one way to do it:

import re

print re.findall(r'\d+\.\S+\d', 'fdgsdfg 100.127.255.255 ggffgsdf 100.64.0.0 asdffsdf')

Output:

['100.127.255.255', '100.64.0.0']

Upvotes: 0

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