parse regex from array

Question

I am trying to parse out IP addresses from Outlook email headers. I've started writing some stuff in C# (because that is the example I was leveraging) and have come up with something close.

I can split the headers with the string lines[] = Regex.Split(headers, @"\r\n"); command okay, but when I try to iterate through the lines[] array, my regex for IP address fails and does not store the value in a second array:

Code:

private void button1_Click(object sender, EventArgs e)
    {
        // use a string constant to define the mapi property
        string PidTagTransportMessageHeaders = @"http://schemas.microsoft.com/mapi/proptag/0x007D001E";
        string mypattern = @"(#{1,3}\.)(#{1,3}\.)([0-9]{1,3}\.)([0-9]{1,3})";
        // string[] ip = Regex.Split(lines[i], (@"(\(|\[)(#{1,3}\.)(#{1,3}\.)([0-9]{1,3}\.)([0-9]{1,3})(\)|\])"));

        // get a handle on the current message
        Outlook.MailItem message = (Outlook.MailItem)this.OutlookItem;

        // use the property accessor to retreive the header
        string headers = string.Empty;

        try
        {
            headers = (string)message.PropertyAccessor.GetProperty(PidTagTransportMessageHeaders);
        }
        catch { 
        }

        //  if getting the internet headers is successful, put into textbox
        string[] lines = Regex.Split(headers, "\r\n");

        Regex regexObj = new Regex(mypattern);

        for (int i = 0; i < lines.Length; i++)
        {
            MatchCollection matches = regexObj.Matches(lines[i]);                       

        }            
        //eventually write the found IP array into textBox1.Text
       textBox1.Text = headers;
        }
    }
}

Any help or suggestions?

What about IPv6 addresses? Can't ignore those anymore these days. — Marc B
– Marc B, Commented Aug 8, 2012 at 19:01
Can you give us an example or two of what the headers variable contains? — Grinn
– Grinn, Commented Aug 8, 2012 at 19:03

Grinn · Accepted Answer · 2012-08-08 20:38:46Z

1

Change your #'s to \d's:

string mypattern = @"(\d{1,3}\.)(\d{1,3}\.)(\d{1,3}\.)(\d{1,3})";

Note that a more accurate IPv4 address capture regular expression would be something like:

\b(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\b

...or at least add word boundaries...

\b(\d{1,3}\.)(\d{1,3}\.)(\d{1,3}\.)(\d{1,3})\b

For a simple IPv6 (standard) I like:

(?<![:.\w])(?:[A-F0-9]{1,4}:){7}[A-F0-9]{1,4}(?![:.\w])

edited Aug 8, 2012 at 20:38

answered Aug 8, 2012 at 19:06

Grinn

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6 Comments

spender Over a year ago

is there a difference between \d and [0-9]? If not, you really should be consistent.

MRAB Over a year ago

\d matches any digit; [0-9] is just a subset.

spender Over a year ago

...consistency question still applies here. Would you want to include the decimal chars of other character sets on the first two octets of an IP address but exclude them from the remainder? [0-9] throughout seems like a better idea.

Grinn Over a year ago

@spender: Actually, I'd go the other direction. \d is just short-hand for [0-9], but you have a good point. Updated.

spender Over a year ago

[0-9] is any digit 0,1,2,3,4,5,6,7,8,9. Apparently there are other digits in unicode that are included in /d

|

user854301 · Accepted Answer · 2012-08-08 19:16:51Z

0

IPAddress.Parse Method do not reinvent the wheel.

answered Aug 8, 2012 at 19:16

user854301

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3 Comments

spender Over a year ago

You have to find them first, or do you propose chucking all the headers at this method? That won't work.

user854301 Over a year ago

Yes all rows could be parsed, why not.

user1585685 Over a year ago

How would you parse the header all at once?

Jason · Accepted Answer · 2012-08-08 19:41:06Z

0

If you're trying to match off IPv4, then try this beast, should be fairly close to what an actual IPv4 can be, the enclosing \b mean beginning and end of a word, so you should be able to remove those and tweak to your heart's content to get the ip based on your header format

\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

answered Aug 8, 2012 at 19:41

Jason

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