How to check an URL is valid with C, C++ language?

Call  'InternetCanonicalizeUrl()' (http://msdn.microsoft.com/en-us/library/aa384342.aspx) and check the return value.

>> use regex to determine valid syntax. ( regular expression )

For that, you'll probably need this :

        http://tools.ietf.org/rfc/rfc3986.txt

(RFC : Uniform Resource Identifier (URI): Generic Syntax)

Howdy....

I think that we misread the question.  Checking to see if a URL is valid (as the original questions asks) goes well beyond checking to see if the URL is properly formatted.


Hi star6868,

To see if a URL is valid, you're going to need to connect to the server at the address in the URL and issue a GET request for the page named on the URL.  Using your example, http://abc.com/ggg/add.html, you're going to have to split it into three basic parts.  The protocol (http://), the IP address or host name (abc.om), and the page (ggg/add.html).  The tools mentioned above can help with this.

Then you're going to have to send the host name to the DNS to retrieve the IP address.

Next, create a client (socket) connection to the IP address on port 80.  (If the URL specified a different port, use it.)

Next, issue a GET ggg/add.html.  This can be a bit tricky.  If the server still supports older HTML, you can issue just the command:

  GET /ggg/add.html'

Otherwise, you'll have to supply a version.

  GET /ggg/addh.html HTTP/1.0

Note that as newer versions are specified, the exchange becomes more conversational.  Older versions were one request, one answer.  Newer versions often want additional information before the page is returned.  The answer from the server will have to be parsed to see if it is a valid page or if an error code is returned.


You included the C++ Builder zone.  It has a lot of built in tools that make this pretty easy.  Using the IDE you can drop a TClient on the form, set the Host and Port variables in the TClient object (Host is the domain name so that the DNS lookup is done for you) and connect to the server.  Then send the GET xxxxx.

You still have to handle the response, but about 1 page of code will get you to the point where you're ready to do that.


Good Luck,
Kent

>> Checking to see if a URL is valid (as the original questions asks) goes well beyond checking to see if the URL is properly formatted.

Good point, but the question asked :

>> How to check systax of URL?

That's why we concentrated on the syntax ;)

star6868

Regular Expressions in C++ with Boost.Regex
http://www.onlamp.com/pub/a/onlamp/2006/04/06/boostregex.html?page=1
http://www.onlamp.com/pub/a/onlamp/2006/04/06/boostregex.html?page=2
http://www.onlamp.com/pub/a/onlamp/2006/04/06/boostregex.html?page=3
http://www.onlamp.com/pub/a/onlamp/2006/04/06/boostregex.html?page=4

http://www.boost.org/libs/regex/doc/index.html

try
{
   boost::regex re("(ftp|http|https)://(w+.)*(w*)/([wd]+/{0,1})+");
   if (!boost::regex_match(url, re))
   {
      throw "Your URL is not formatted correctly!";
   }
}
catch (boost::regex_error& e)
{
   cerr << "The regexp " << re << " is invalid!" << endl;
   throw(e);
}

                                              

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@deadrop

sorry, but how to install Boost.Regex?

with Visual C, or GCC ?

error LNK2001: unresolved external symbol __imp__InternetCanonicalizeUrlA@16
Release/Test.exe : fatal error LNK1120: 1 unresolved externals

system require: schannel.lib

But have not this file!

Where to get this file?

rjohnsonjr,

I can help if you have questions. If not, please close this question.
Thank you.

Where is schannel.lib ?
How can I download this file?