Re: Regexp to match IP address

[dsb]

Where's japhy when you need 'em. :)

I guess it kind of depends on how concerned you are with the validity of your data. Testing for 4 1-3 digit numbers seperated by dots is easy:

m/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\$/;

If you are interested making sure IP's are valid, you could do a couple of things.

One, using the above regex, you could grab the digits and test them individually.

use strict;
my @nums;
my $IP = "127.0.0.1"
(@nums) = $IP =~ m/^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/;

# test each for <= 255 here.
# also make sure its not 0.0.0.0

Or you could use a more complicated regex to test for validity during the pattern matching. From O'Reilly's Mastering Regular Expressions:

m/^([01]?\d\d?|2[0-4]\d|25[0-5])\.([01]?\d\d?|2[0-4]\d|25[0-5])\.
   ([01]?\d\d?|2[0-4]\d|25[0-5])\.([01]?\d\d?|2[0-4]\d|25[0-5])$/;

UPDATE: I just realized this was my 150th post. Yay for me. :)

[kamleein]

Hi below code validates the IP adress. Please do let me know how this can be enhanced so that it is more readable. The validations considered are listed below. 1) If the length of any part of the IP adress seperated by the decimal is more than one digit, then it should not start with zero. 2) The first part of the IP adress seperated by the decimal cannot be zero. 3) Any part of the IP adress seperated by the decimal cannot be more than 255. 4) IP address should contain only 3 decimals. 5) The numbers cannot be negative. print "Enter the IP address : "; $ip = <stdin>; if($ip =~ /^(3-9\d?|1\d?\d?|2(0-5?0-5?|6-9?))\.(0|3-9\d?|(1\d?\d?|2(0-5?0-5?|6-9?)))\.(0|3-9\d?|(1\d?\d?|2(0-5?0-5?|6-9?)))\.(0|3-9\d?|(1\d?\d?|2(0-5?0-5?|6-9?)))$/) { print "Correct\n"; } else { print "Wrong\n"; }