Perl regular expression to match an IP address

Question

I have written this code, but it does not work. Can someone point out the issue?

sub match_ip()
{
  my $ip = \"The IP address is 216.108.225.236:60099\";
  i         


        

Answer 1

Though there are well documented and tested modules at CPAN to match and validate IP addresses but there must be some solid reason for you not to use it. Personally I never had a real reason to use them for validation purpose either since I trusted/feeded the input.

Here is a shorter version of your regex, with it's own pitfalls:

while (my $ip = )  {
    chomp $ip;
    # older version
    # if($ip =~ /(\d{1-3}\.\d{1-3}\.\d{1-3}\.\d{1-3}\:\d{1-5})/)

    # see below for explanation
    if ($ip =~ /\b(\d{1,3}(?:\.\d{1,3}){3}:\d{1,5})\b/)
    {
        print "$ip - matches\n";
    } else {
        print "$ip - does not match\n";
    }
}

__DATA__
216.108.225.236:60099
4.2.2.1:1
216.108.225.236:0
1216.1108.1225.1236:1234
216.108.225.236x:123
9216.108.225.236:8472
10.10.10.10

Results:

216.108.225.236:60099 - matches
4.2.2.1:1 - matches
216.108.225.236:0 - matches
1216.1108.1225.1236:1234 - does not match
216.108.225.236x:123 - does not match
9216.108.225.236:8472 - does not match
10.10.10.10 - does not match

Explanation:

/\b             # word boundary
(               # start memory capture group 1
\d{1,3}         # one to three digits, first octat
(:?             # start non memory capture group, notice ?:
  \.\d{1,3}     # a literal dot followed by an ip octet
)               # end non memory capture group
{3}             # three times of dots and ip octets
:               # match a colon
\d{1,5}         # port number, one to five digits
)               # end of memory capture group 1
\b              # word boundary

Hope this helps.