valadating a url

by NicheExposed

Posted: 14 years ago 12 replies

PROGRAMMING

Thanks for everyone who helped me with the first problem but I have one more. I need to validate that a url is typed into the text box before a user clicks on the button to send the url to the webbrowser control.

basically I need it to do this....

When a user types in the complete url http://www.yoursite.com and then hits the go button it will take them to the url. But if they type in anything but a valid url I want it to display a message box and preventing them from visiting a page. If anyone types in anything but a valid url the program will crash. How do I validate that it is a valid url and not garbage.

Thanks

#url #valadating

jwlnewsome 14 years ago

Hi, try pinging the url before you preform the action. There are a few php scripts out there that can ping addresses to see if there is a response. I would personally cURL the url to see if i get anything back other than a 404 error
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NicheExposed 14 years ago

i am working in vb.net writing an exe program. I am using a webbrowser control, text box and a button.
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warmlikecoffee 14 years ago

You can do something like this:

If Texbox1.Text.Substring(0,7) = "hxxp://" Or Textbox1.Text.Substring(0, 4) = "wwvv." Then
MessageBox.Show("This is a URL")
End If

The code checks the first letters of your Textbox1, if it begins with hxxp:// or wwvv. then it is deemed as a valid URL.

If you need more help just let me know, I can help when I have free time.

EDIT:
Change the xx to tt and vv to w, the forum wouldn't let me post a link due to my post count.
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- Mike P Smith 14 years ago
  
  If you really want a challenge (and earn your geek stripes) try using "Regular Expressions" - I think there are libraries available for VB.NET if that is your platform.
  
  That can validate a URL rather well with just one statement.
  
  --
  Mike Smith
  No sig, no shirt, no sale.
  
  Thanks
  
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Johnathan 14 years ago

Although I`m not too familiar with vb.net, I`m assuming its similar to VB6. Simply navigate to the URL, and if nothing is there, then you know its not valid. I.e., webbrowser1.navigate \"whatever.com\" then check the \'location\' attribute, etc.
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NicheExposed 14 years ago

I ended up calling a programming friend of mine who gave me the code. I had to create a function. here is the code if anyone else needs it.

PrivateFunction UrlIsValid(ByVal url AsString) AsBoolean
Dim is_valid AsBoolean = False
If url.ToLower().StartsWith("www.") Then url = _
"http://" & url
Dim web_response As HttpWebResponse = Nothing
Try
Dim web_request As HttpWebRequest = _
HttpWebRequest.Create(url)
web_response = _
DirectCast(web_request.GetResponse(), _
HttpWebResponse)
ReturnTrue
Catch ex As Exception
ReturnFalse
Finally
IfNot (web_response IsNothing) Then _
web_response.Close()
EndTry
EndFunction
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mywebwork 14 years ago

Originally Posted by NicheExposed

If anyone types in anything but a valid url the program will crash.

Just a thought, you might consider writing an Error Handler as well - having the program crash if it receives a bad URL is not particularly user-friendly!

Keep in mind that the user may enter a valid URL by clicking on an invalid hyperlink within a web page. That bad URL will probably make it past your URL format check.

Beat of luck with your project...

Bill
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NicheExposed 14 years ago

when someone clicks on a link in a web page that is bad will just return a page can not be displated error. That has nothing to do with the coding problem within the software.
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AndyBlackSEO 14 years ago

For php you would use regex (regular expression) to determine whether a url is in a valid format. You could then go one further by using cURL to grab the contents of the page and verify that a valid live webpage exists at the end of it. I'm creating this functionality for my latest product and it works perfectly.

What platform are you wanting to code this in? web app or a windows application?
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Gimme4Free 14 years ago

CURL:

PHP Code:

function url_exists() { VAR1 = curl_init(); if (false === VAR1) { return false; } curl_setopt(VAR1, CURLOPT_HEADER, true); curl_setopt(VAR1, CURLOPT_FAILONERROR, true); curl_setopt(VAR1, CURLOPT_HTTPHEADER, Array("User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.15) Gecko/20080623 Firefox/2.0.0.15") ); curl_setopt(VAR1, CURLOPT_NOBODY, true); curl_setopt(VAR1, CURLOPT_RETURNTRANSFER, true); VAR2 = curl_exec(VAR1); curl_close(VAR1); if (preg_match('/200 OK/i',substr_replace(VAR2,'',30))) { return true; }else{ return false; } }

Replace VAR1 with $ something and VAR2 with $ something else (WF wont let me post up proper variables)
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sanjid112 14 years ago
You can try this regex.

CODE-one linear ($urlregex):

PHP Code:

   = "^(https?|ftp)://([a-z0-9+!*(),;?&=.-]+(:[a-z0-9+!*(),;?&=.-]+)?@)?[a-z0-9+-]+(.[a-z0-9+-]+)*(:[0-9]{2,5})?(/([a-z0-9+-].?)+)*/?(?[a-z+&.-][a-z0-9;:@/&%=+.-]*)?(#[a-z_.-][a-z0-9+.-]*)?$"; if (eregi(, )) {echo "good";} else {echo "bad";}

(OPTIONAL: Read more for some explanations

it will validates all this type of url ($url)

PHP Code:

// valid urls = "https://user:pass@www.somewhere.com:8080/login.php?do=login&style=%23#pagetop"; = "http://user@www.somewhere.com/#pagetop"; = "https://somewhere.com/index.html"; = "ftp://user:****@somewhere.com:21/"; = "http://somewhere.com/index.html/";  //this is valid!!

The CODE-broken into section for easy editing and understanding ($urlregex):

PHP Code:

// SCHEME = "^(https?|ftp)://"; // USER AND PASS (optional) .= "([a-z0-9+!*(),;?&=.-]+(:[a-z0-9+!*(),;?&=.-]+)?@)?"; // HOSTNAME OR IP .= "[a-z0-9+-]+(.[a-z0-9+-]+)*";  // http://x = allowed (ex. http://localhost, http://routerlogin) // .= "[a-z0-9+-]+(.[a-z0-9+-]+)+";  // http://x.x = minimum // .= "([a-z0-9+-]+.)*[a-z0-9+-]{2,3}";  // http://x.xx(x) = minimum //use only one of the above // PORT (optional) .= "(:[0-9]{2,5})?"; // PATH  (optional) .= "(/([a-z0-9+-].?)+)*/?"; // GET Query (optional) .= "(?[a-z+&.-][a-z0-9;:@/&%=+.-]*)?"; // ANCHOR (optional) .= "(#[a-z_.-][a-z0-9+.-]*)?$"; // check if (eregi(, )) {echo "good";} else {echo "bad";}

All the lines can be safely removed (except for the hostname) if you do not want allowing some URL segment (if you don't want getqueries in your urls, just comment the respective $urlregex .= ....) - but do not reorder them.
the "(optional)" states that the part MAY exist, but url will be valid even if it doesn't contain the part (see the valid urls above).

syntax:
Code:

<http[s]|ftp> :// [user[:pass]@] hostname [port] [/path] [?getquery] [anchor]
- take into account allowed safe characters
- assumption .. (double dot) is never allowed in hostname or path.
-Malik

PS. please tell me if it is wrong to paste the code here. and wait for some feedbacks
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- Mike P Smith 14 years ago
  
  Nice post, sanjid112.
  
  For VB.NET, using sanjid112's regex, this is what you need:
  
  If Not Regex.IsMatch(myURL, "^(https?|ftp)://([a-z0-9+!*(),;?&=.-]+(:[a-z0-9+!*(),;?&=.-]+)?@)?[a-z0-9+-]+(.[a-z0-9+-]+)*(:[0-9]{2,5})?(/([a-z0-9+-].?)+)*/?(?[a-z+&.-][a-z0-9;:@/&%=+.-]*)?(#[a-z_.-][a-z0-9+.-]*)?$")Then
  ' write your error code
  ' here.
  Else
  ' write your success code here
  End If
  
  --
  Mike Smith
  No advertising in my Sig. What am I thinking?
  
  Thanks
  
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valadating a url

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