regex multiple ip addresses from a string

Question

I have a string which contains multiple ip addresses like so:

 String header = "Received: from example.google.com ([192.168.0.1]) by example.google.com ([192.168.0.2]) with mapi; Tue, 30 Nov 2010 15:26:16 -0600";

I want to use regular expression to get both IP's from this. I so far my code looks like this

public String parseIPFromHeader(String header) {
    Pattern p = Pattern.compile("\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b");
    Matcher m = p.matcher(header);
    boolean matchFound = m.find();

    System.out.println(matchFound);

    if (matchFound) {
         // Get all groups for this match
        for (int i=0; i<=m.groupCount(); i++) {
            // Get the group's captured text
            String groupStr = m.group(i);

            // Get the group's indices
            int groupStart = m.start(i);
            int groupEnd = m.end(i);

            // groupStr is equivalent to
            System.out.println(header.subSequence(groupStart, groupEnd));
        }
    }
}

but I never get match. Am I approaching this correctly? Thanks

You've already fully (over-)specified the IP digit pattern, so there's no point in forcing \b anchors. — Marc B
– Marc B, Commented Nov 29, 2011 at 16:07
ahhh thanks! that did the trick, well at least I am getting matches., is there anyway I can get both? like loop through the matches? It seems to only find the first one. — medium
– medium, Commented Nov 29, 2011 at 16:08
There is a point to the \bs, without them (part of) 1234.1.1.1234 would match. — Qtax
– Qtax, Commented Nov 29, 2011 at 16:14

Qtax · Accepted Answer · 2011-11-29 16:12:08Z

6

You escaped \ characters before dots, but if i remember correcly, you need escape it in \b sequence too, so replace them with \\b

edited Nov 29, 2011 at 16:12

Qtax

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answered Nov 29, 2011 at 16:08

Gabor Garami

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bongi · Accepted Answer · 2011-11-29 16:19:44Z

0

If you only need the IP adresses you can greatly simplify your regex to match just those

"([0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3})" //not perfect, i know...

And then use Matcher.find() multiple times to find all occurences in the string

while(m.find()) {
    String ip = m.group(1) //the first group is at index 1, group 0 is the whole match. (Does not actually make any difference here)
}

answered Nov 29, 2011 at 16:19

bongi

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