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

You can also use the following regex to make sure that the quad's aren't bigger then 255, it also "reuses" the digit matching instead of copypasting it 4 times.

my $rx = qr/^(?!(\.))(\.?(\d{1,3})(?(?{$^N > 255})(*FAIL))){4}$/;
if('192.168.1.2' =~ $rx){
  print "OK\n";
}

It uses a few features from perl regex matching (man perlre):

• (*FAIL): stops pattern matching and fails
• (?(condition)...): conditional match
• (?{ code }): used within that condition

Answer 2

Replace the dashes with commas.

/(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\:\d{1,5})/

Answer 3

Change {1-3} to {1,3} same for {1-5} -> {1,5}

Answer 4

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 = <DATA>)  {
    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.

Answer 5

This might help:

my $ip = "195.249.61.14";

my @ips = (
    "set protocols bgp group IBGP-RRCL-CUSTOMER neighbor 195.249.61.142",
    "set protocols bgp group IBGP-RRCL-CUSTOMER neighbor 195.249.61.14",
    "set protocols bgp group IBGP-RRCL-CUSTOMER neighbor 195.249.61.141"
);

foreach (@ips) {
   print "$_\n" if ( /\b$ip\b/ );
}

Output:

set protocols bgp group IBGP-RRCL-CUSTOMER neighbor 195.249.61.14

Answer 6

$ip = "10.255.256.1";

# will accept valid ips
if ($ip =~ m/^([1|2][0-9]{1,2})\.([0-255]{1,3}\.){2}[0-255]{1,3}/ && ($1 <=255)) {

  print "This is a valid ip: $ip \n";
 } else {
   print "This is not a valid ip: $ip \n";
}