Extract substring from string

[bigbang]

i have a small console program that shows you, your ip and resolves from your ip your host name(reverse dns) and display then your ip and host name
to the screen.
an example output:

IP: 12.34.567.89
Host Name: dslb-012-034-567-089.pools.myisp-ip.net

now i want to convert the

dslb-012-034-567-089.pools.myisp-ip.net

to

dslb.pools.myisp-ip.net

or something similar.
my goal is to remove the numbers and the "-" character from the host name string, because my ip is a dynamic ip and it changes every
24hrs automatically. it should start to find the first "-" character and from there, until the first "." character or last
number in the host name string and then cut out the found unneeded characters and then display the final host name string without the ip and
the "-" character.
i'm using msvc++ as compiler.

how would i do that?

any help and hints are more than welcome.

[f1shrman]

There are many ways of doing this in C++....here are two examples, one using c style strings and another using std::string:

#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <string>
using namespace std;
int main( int argc, char** argv )
{
//----------------------------------------------------------------
//-- using old c string routines
//----------------------------------------------------------------
char strResult[100] = { NULL };
int strPosition = 0;
char* testValue = "dslb-012-034-567-089.pools.myisp-ip.net";
 
//-- get the position of the first dash and period
char* strFromFirstDash = strchr( testValue, '-' );
char* strFromFirstPeriod = strchr( testValue, '.' );
 
//-- now find out how long the first string section is 
strPosition = (strFromFirstDash -testValue);
 
//-- build the new string
strncpy( strResult, testValue, strPosition );
strncat( strResult, strFromFirstPeriod, (99 - strPosition ));
 
printf( "Using C string manipulation - %s\n", strResult );
 
//----------------------------------------------------------------
//-- using std::string
//----------------------------------------------------------------
string stringValue = "dslb-012-034-567-089.pools.myisp-ip.net";
 
//-- get the position of the first dash and period 
int dashPosition = stringValue.find_first_of( '-' );
int periodPosition = stringValue.find_first_of( '.' );
 
//-- build the new string removing the section we don't want 
string stringNewValue = stringValue.substr(0, dashPosition );
stringNewValue.append( stringValue.substr( periodPosition,
					 stringValue.length() - periodPosition));
 
printf( "Using std::string - %s\n", stringNewValue.c_str() );
 
return 0;
}

NOTE: Error / Exception checking should be added.

HTH

[bigbang]

thanks f1shrman, i could solve it with help from a good online friend, his hint was to use:

#include <stdio.h>

void main()
{
char host[]="dslb-012-034-567-089.pools.myisp-ip.net";

printf("\n %s ", host);
strcpy(strchr(host,'-'),strchr(host,'.'));
printf("\n %s",host);

}

output:

 dslb-012-034-567-089.pools.myisp-ip.net 
 dslb.pools.myisp-ip.net

and i modified it to:

	char* cShortHost = host->h_name;
	strcpy(strchr(cShortHost, '-'), strchr(cShortHost, '.'));

	printf("\nShortHost Name: %s", cShortHost);

[greg_dolley]

and i modified it to:
char* cShortHost = host->h_name;
strcpy(strchr(cShortHost, '-'), strchr(cShortHost, '.'));

printf("\nShortHost Name: %s", cShortHost);

Remember, the h_name member of "host" you do not own. Winsock determines when this string is deallocated. So you shouldn't mess with its pointer. You should make cShortHost a copy of host->h_name.

-Greg Dolley

[bigbang]

Remember, the h_name member of "host" you do not own. Winsock determines when this string is deallocated. So you shouldn't mess with its pointer. You should make cShortHost a copy of host->h_name.

-Greg Dolley

interesting. you mean like that?

    printf("IP: %s", cIP);
	printf("\nHost Name: %s", host->h_name);

	WritePrivateProfileString("IP Info", "IP",   cIP,          "c:\\IPtoHOST.ini");
	WritePrivateProfileString("IP Info", "HOST", host->h_name, "c:\\IPtoHOST.ini");

	strcpy(strchr(host->h_name, '-'), strchr(host->h_name, '.'));

	printf("\nShortHost Name: %s", host->h_name);

    WSACleanup();

	WritePrivateProfileString("IP Info", "SHORT HOST", host->h_name,   "c:\\IPtoHOST.ini");
	MessageBox(NULL, "IP Info has been printed in C:\\IPtoHOST.ini", "IP Check", MB_OK);

output will be like that:

IP: 12.34.567.89
Host Name: dslb-012-034-567-089.pools.isp-ip.net
ShortHost Name: dslb.pools.isp-ip.net

p.s. can someone tell me where i can find here the codeformatbutton in the thread options?

test

edit: found out i can use and type manualy [code][\code].

[greg_dolley]

No, you're still modifying host->h_name. You need to make a copy of h_name first, then do the manipulation, like this:

char *host_name = NULL;

host_name = (char *)malloc(sizeof(char)*(strlen(host->h_name)+1));
strcpy(host_name, host->h_name);

-Greg Dolley

[greg_dolley]

Forgot something: now you just use the host_name variable to do all your manipulation.

-Greg Dolley

[bigbang]

Forgot something: now you just use the host_name variable to do all your manipulation.

-Greg Dolley

Thank you alot greg_dolley.
here's the win32 console program i was working on.

//IPtoHOST.cpp

#include <windows.h>
#include <wininet.h>
#include <stdio.h>

#pragma comment(lib, "Ws2_32.lib")
#pragma comment(lib, "wininet.lib")

#define AUTHOR "bigbang"

char cIP[12];
char* host_name = NULL;

int initWinSock()
{
	WORD wVersionRequested;
	WSADATA wsaData;
	int err;
    
	wVersionRequested = MAKEWORD(1, 1);
	err = WSAStartup(wVersionRequested, &wsaData);

	if (err != 0)
	{
		return -1;
	}
	return 0;
} 

void GetIP()
{
	HINTERNET hInet, hUrl;
	DWORD     dwCode, dwLen;

	if (NULL == (hInet = InternetOpen(TEXT("InetURL:/1.0"), INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0)))
	printf("Unsuccessful InternetOpen\r\n");

	else
	{
		printf("");

		if (NULL != (hUrl = InternetOpenUrl(hInet, "http://iptohost.ip.funpic.de/ipcheck.php", NULL, 0, INTERNET_FLAG_RELOAD, 0)))
		{
			dwCode = 0;
			dwLen  = sizeof(dwCode);

			HttpQueryInfo(hUrl, HTTP_QUERY_STATUS_CODE, &dwCode, &dwLen, 0);
			if ((dwCode == '002') || (dwCode == '203'))
			{
				if (InternetReadFile(hUrl, cIP, 256, &dwLen))
				{
					cIP[12] = '\0';
				}
			}
			InternetCloseHandle(hUrl);
		}
		else
		printf ("Apparently no valid url!\r\n");
	}
	InternetCloseHandle(hInet);
}

int main()
{
	system("color 9F");
	printf("+---------------------+\n");
	printf("+ IPtoHOST by %s +\n", AUTHOR);
	printf("+---------------------+\n\n");

	GetIP();

    struct hostent *host;
    struct in_addr addr;

    if (initWinSock())
	{
        printf("Error! Can't initialize winsock\n");
        return 1;
    }

    addr.s_addr = inet_addr(cIP);
    if (addr.s_addr == INADDR_NONE)
	{
        host = gethostbyname(cIP);
    }
    else
	{
        host = gethostbyaddr((const char *)&addr, sizeof(struct in_addr), AF_INET);
    }

    if (host == NULL)
	{
        printf("Cannot resolve address %s. Error code: %d\n", GetIP, WSAGetLastError());
        return 1;
    }

    printf("IP: %s", cIP);
	printf("\nHost Name: %s", host->h_name);

	WritePrivateProfileString("IP Info", "IP",   cIP,          "c:\\IPtoHOST.ini");
	WritePrivateProfileString("IP Info", "HOST", host->h_name, "c:\\IPtoHOST.ini");

	host_name = (char *)malloc(sizeof(char)*(strlen(host->h_name)+1));
	strcpy(host_name, host->h_name);

	strcpy(strchr(host_name, '-'), strchr(host_name, '.'));

	printf("\nShortHost Name: %s", host_name);


    WSACleanup();

	WritePrivateProfileString("IP Info", "SHORT HOST", host_name,   "c:\\IPtoHOST.ini");
	MessageBox(NULL, "IP Info has been printed in C:\\IPtoHOST.ini", "IP Check", MB_OK);

	free(host_name);

    return 0;
}

//ipcheck.php

<?
$ipadresse ="$REMOTE_ADDR"; 
echo "$ipadresse";
?>

i think the hname pointer problem is fixed now?

output is:

IP: 12.34.567.89
Host Name: dslb-012-034-567-089.pools.isp-ip.net
ShortHost Name: dslb.pools.isp-ip.net

[greg_dolley]

i think the hname pointer problem is fixed now?

There ya go! Much better.

One more thing: remember to free the "host_name" string before exiting. Just, "free(host_name);" will do the trick.

Greg Dolley

[Paul McKenzie]

Thank you alot greg_dolley.
here's the win32 console program i was working on.

Your code has a memory leak. You called malloc() without calling free() to release the memory.

Regards,

Paul McKenzie