Comments on: Using regular expressions to validate IP address with Delphi XE

By: Andreano Lanusse

Andreano Lanusse — Thu, 12 Jan 2012 07:59:45 +0000

In reply to Carl.

Carl,

You can use RegExp in C++ as I describe in this blog post http://www.andreanolanusse.com/en/using-regular-expression-on-cbuilder-firemonkey-application/

By: Carl

Carl — Sun, 31 Jul 2011 15:15:38 +0000

How can I use this component for C++ Builder XE? My friend Brent and I are trying to use regex’s to parse content from Web Responses.

By: Andreano Lanusse

Andreano Lanusse — Tue, 26 Oct 2010 04:15:07 +0000

In reply to Please Help me!. Alexander, the ipWorks components included in Delphi XE has many internet components, one of them is the Ping component, it does what are you looking for.

By: Please Help me!

Please Help me! — Thu, 21 Oct 2010 16:35:21 +0000

Help Me ,My Dear Friend!
I Want Create A program With Delphi7,that Ping Many Ips in one Time(Real Time).
please Send for me your Standard Delphi7 request in : Alexander.Alkhine@gmail.com
thank you.

By: Fabricio

Fabricio — Wed, 15 Sep 2010 17:22:28 +0000

@John
Andreano, compare your regexp with normal Delphi code one would use to do the validation: the code will be simpler, clearer, more maintainable and likely faster.
I believe it can clearer and more *readable*. Simpler I have some doubt. And I’m pretty sure that, for getting information on large strings, nothing can be faster than regex… (Unless Emb implementation had done something much wrong).
Regex is (maybe just one of them) the little secret that makes PERL almost invincible in text processing.

By: Andreano Lanusse

Andreano Lanusse — Tue, 14 Sep 2010 19:40:39 +0000

In reply to john. I understand John, but you can assume all of your strings will come from Delphi Applications, for example if you have a REST Server and need to get the content of HTML Input, you will need to parse the content which I think you will have more work then only use a RegExp. I will blog more about that and will show how to write a clear code using RegExp.

By: john

john — Tue, 14 Sep 2010 12:10:17 +0000

Well goto is powerful too, and it can allow to do more with less code, doesn’t mean you want to use it.

Andreano, compare your regexp with normal Delphi code one would use to do the validation: the code will be simpler, clearer, more maintainable and likely faster.

By: Stefan

Stefan — Fri, 10 Sep 2010 18:13:36 +0000

@John: RegExps are very powerful, you have to learn how to use them if you are not familar with them. Prolly a case for solid unit testing.

@Andreano: Yes, simply change the \b at the beginning to ^ and the \b at the end to $. 😉

By: Andreano Lanusse

Andreano Lanusse — Fri, 10 Sep 2010 13:51:17 +0000

@John, it’s not friendly the regexp mask, but it doesn’t mean it is not useful.

This is just a example how to use and it is very useful, I could create a separated function and make the code clear putting the regexp mask in other function.

By: Andreano Lanusse

Andreano Lanusse — Fri, 10 Sep 2010 13:48:30 +0000

Interesting Stefan, so I had to change the regexp I used to not allow that 🙂

By: john

john — Fri, 10 Sep 2010 06:45:50 +0000

This post is a good example of why you don’t want regexps in your code: not only it is messy to look at, but it is also obviously hard to figure out if the regexp is correct or not (see the various comments above!)

By: Stefan

Stefan — Thu, 09 Sep 2010 12:59:53 +0000

Nope, you are using word boundaries instead of start and end of string anchors. “Hello 127.0.0.1 World” would match the regex.

By: Andreano Lanusse

Andreano Lanusse — Thu, 09 Sep 2010 12:49:48 +0000

In reply to Stefan.

Hi Stefan, it will check if the IP address is valid, as well it will restrict the 4 numbers in the IP address to 0..255.

But if you are considering if the IP address is valid on the network, not I’m not doing that, you can use the IP works ping component to check that 🙂

By: Stefan

Stefan — Thu, 09 Sep 2010 12:21:03 +0000

Actually your example checks if the given text *contains* a valid IP adress, not if it *is* a valid IP adress.

By: Andreano Lanusse

Andreano Lanusse — Thu, 09 Sep 2010 12:01:18 +0000

In reply to Uwe Raabe. All sorry, it was a typo from my side, the second example finish with 263 and the output message said DOES NOT match, so the program is correct, again my typo :)

By: Uwe Raabe

Uwe Raabe — Thu, 09 Sep 2010 08:47:15 +0000

@Atle: The output actually states that the IP address is correct!

By: Atle

Atle — Thu, 09 Sep 2010 08:24:40 +0000

This is wrong:
“In this case not, the IP address finish with 243, it is out of the range which is 255”..

243 is not outside the range.

By: Michael Justin

Michael Justin — Thu, 09 Sep 2010 08:03:06 +0000

Hint: a simple number like 123456789 is also a valid IP address (if it is in the IPv4 or IPv6 address range). The dot-decimal notation is only the usual representation. Try it with “ping 123456789”.

By: Jeroen Pluimers

Jeroen Pluimers — Thu, 09 Sep 2010 07:43:33 +0000

This is in fact a much better example than the eternal email address validation (which – when you read the RFC’s closely – can only be approximated by regular expressions).

–jeroen

By: pedrow

pedrow — Thu, 09 Sep 2010 07:31:43 +0000

Can you just check, is your second example right?