Regex to extract only IPv4 addresses from text

问题

I've tried to extract only IP addresses from the the given example input, but it extracts some text with it. Here's my code:

$spfreccord="v=spf1 include:amazonses.com include:nl2go.com include:smtproutes.com include:smtpout.com ip4:46.163.100.196 ip4:46.163.100.194 ip4:85.13.135.76 ~all";

 $regexIpAddress = '/ip[4|6]:([\.\/0-9a-z\:]*)/';        
 preg_match($regexIpAddress, $spfreccord, $ip_match);
 var_dump($ip_match);

I'm looking to match only the IPv4 IP address xxx.xxx.xxx.xxx in each column of the table, but it looks like that the $regexIpAddress is not correct.

Can you please help me find the correct regex to extract only the IPv4 IP addresses? Thanks.

回答1:

Use the following regex:

/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}(?:\/\d{2})?/

So for this:

$spfreccord="v=spf1 include:amazonses.com include:nl2go.com include:smtproutes.com include:smtpout.com ip4:46.163.100.196 ip4:46.163.100.194 ip4:85.13.135.76 cidr class v=spf1 ip4:205.201.128.0/20 ip4:198.2.128.0/18 ~all";

 $regexIpAddress = '/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}(?:\/\d{2})?/';        
 preg_match_all($regexIpAddress, $spfreccord, $ip_match);
 var_dump($ip_match);

Gives:

array(1) {
  [0]=>
  array(5) {
    [0]=>
    string(14) "46.163.100.196"
    [1]=>
    string(14) "46.163.100.194"
    [2]=>
    string(12) "85.13.135.76"
    [3]=>
    string(16) "205.201.128.0/20"
    [4]=>
    string(14) "198.2.128.0/18"
  }
}

回答2:

You want preg_match_all(), and a slight modification of your regex:

php >  $regexIpAddress = '/ip4:([0-9.]+)/';
php >  preg_match_all($regexIpAddress, $spfreccord, $ip_match);
php >  var_dump($ip_match[1]);
array(3) {
  [0]=>
  string(14) "46.163.100.196"
  [1]=>
  string(14) "46.163.100.194"
  [2]=>
  string(12) "85.13.135.76"
}
php >

You don't need to match against a-z; it's not a valid part of an IP address, 4 or 6. Since you said you only want IPv4, I've excluded any matching of IPv6 addresses.

If you wanted to include IPv6 as well, you can do this:

php > $regexIpAddress = '/ip[46]:([0-9a-f.:]+)/';
php > preg_match_all($regexIpAddress, $spfreccord, $ip_match);
php > var_dump($ip_match[1]);
array(4) {
  [0]=>
  string(14) "46.163.100.196"
  [1]=>
  string(14) "46.163.100.194"
  [2]=>
  string(12) "85.13.135.76"
  [3]=>
  string(39) "2001:0db8:85a3:0000:0000:8a2e:0370:7334"
}

来源：https://stackoverflow.com/questions/37640920/regex-to-extract-only-ipv4-addresses-from-text

标签

php

regex

spf