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

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!

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

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

Quote:

---

Originally Posted by 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

---

What happens if the host name begins with a number?

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 :)

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:

Code:

---

        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.

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

Quote:

---

Originally Posted by _Superman_

Just check if the first character is a digit

---

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

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

Quote:

---

Originally Posted by _Superman_

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.

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

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:

Code:

---

#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");
}

---

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

Can you do this without making IsAlpha a class?

Thanks

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