determining if a string is an ip address or a hostname?

[lab1]

Hello,

Is it possible to determine is a string is an ip address or a hostname? I need to be able to differentiate between the two.

Thanks!

[GCDEF]

An IP address is numer . number . number . number. That should be easy enough to check for.

[newbie30]

You could do it this way:


Sorry dont know how to use code blocks, can some one tell us


char *str="12.34.34.34:0.0";

if(str[0] > '9')
cout<<"not ip address"<<endl;
else
cout<<"ip address"<<endl;


Hope this helps

[GCDEF]

You could do it this way:


Sorry dont know how to use code blocks, can some one tell us


char *str="12.34.34.34:0.0";

if(str[0] > '9')
cout<<"not ip address"<<endl;
else
cout<<"ip address"<<endl;


Hope this helps

What happens if the host name begins with a number?

[newbie30]

I was assuming that either his ip address was in this format:

10.2.1.10:0.0 or a total string format ie asmith:0.0

yes i know i shouldnt assume

[Red Squirrel]

This code calls up a lot of custom stuff that won't compile but may be of help to know how to go about it:

	bool ValidateIP(string ip)
	{
		xVector<string> exploded = Parser::Explode(ip,".");
		
		if(exploded.GetSize()!=4)return false;
		
		string tmp;
		for(int i=0;exploded.Get(tmp,i);i++)
		{
			int octet = BitStream::Str2Int(tmp);
			if(octet<0 || octet>255)return false;
		}
		
		return true;
	}

Basically you want to explode the string by ".", then make sure that all you have is 4 ints, and that they are between 0 and 255.

[_Superman_]

Just check if the first character is a digit
isdigit(ipaddress[0])

[laserlight]

Just check if the first character is a digit

In post #4, GCDEF asked: "What happens if the host name begins with a number?"

[_Superman_]

The following code snippet is from MSDN sample code for the function gethostbyaddr

if (isalpha(host_name[0])) { /* host address is a name */
printf("Calling gethostbyname with %s\n", host_name);
remoteHost = gethostbyname(host_name);
} else {

http://msdn.microsoft.com/en-us/libr...21(VS.85).aspx

[laserlight]

The following code snippet is from MSDN sample code for the function gethostbyaddr

In that case the sample code has a bug since GCDEF's point seems valid to me.

[_Superman_]

If the hostname is given something like 123greetings.com, then it would be a problem.
Names beginning with http:// or www would be fine.

[PredicateNormative]

You could always check the string to see if it contains letters... there is probably a more efficient and/or concise way of doing this, but something like the following should work:

#include <iostream>
#include <string>
#include <cctype>     //for tolower
#include <algorithm>  //for std::find_if
#include <functional> //for std::unary_function

class IsAlpha : public std::unary_function<char,void>
{
public:
  bool operator()(char c)
  {
    int val = tolower(c);
    return (val>='a' && val<='z');
  }
};

bool ContainsAlpha(const std::string& s)
{
  return(s.end() != std::find_if(s.begin(), s.end(), IsAlpha())); 
}

int main()
{
  std::cout << ContainsAlpha("192.168.0.1:8080") << std::endl;
  std::cout << ContainsAlpha("123greetings.com") << std::endl;
  
  system("PAUSE");
}

[GNiewerth]

When there&#180;s no parsing include you can assume the following:
If it&#180;s a IPv4 address the string must consist of three dots ("."), everything else must be digits (0-9). If this rule is violated the address is either a logical host name or corrupt

Edit:
Way too late

[lab1]

Can you do this without making IsAlpha a class?

Thanks

[Russco]

IsAlpha() alone wont work for IPv6 addresses, the OP didn't state whether he was supporting IPv6. I think regex maybe a better solution?