Reading txt file with ifstream goes wrong

[roarkr]

Hi,


I have the following code that reads an ip address ( i.e. 192.168.0.199) from a txt file. The txt file has only 1 line and that is the ip address.

The readfile (); read the ip address into ipaddr OK, but when returning to caller mess the ipaddr up.

Can anyone see what I am doing wrong here?

rgs

int readfile()
{

            ifstream stream1("D:\\file1.txt");
            char a[80];
            if(!stream1)
            {
                        cout << "While opening a file an error is encountered" << endl;
            }
            else
            {
                       cout << "File is successfully opened" << endl;


            }
            while(!stream1.eof())
            {
                        stream1 >> a;
                        string ipaddr = a;
		

//Sleep ( 1000);
            }
            return(0);
 }

[TheDestroyer]

Your program is probably over-writing the value before it finishes. Try a vector approach:

#include <vector>
int readfile()
{

            ifstream stream1("D:\\file1.txt");
            char a[80];
            std::vector<std::string> readdata;
            if(!stream1)
            {
                        cout << "While opening a file an error is encountered" << endl;
            }
            else
            {
                       cout << "File is successfully opened" << endl;


            }
            while(!stream1.eof())
            {
                        stream1 >> a;
                        readdata.push_back(a); //now readdata is an array with everything read from the file
//Sleep ( 1000);
            }
            return(0);
 }

[roarkr]

Hi,

Thanks, now I am almost OK



I now have the ip address in the readdata [1], but how do I

write it to the ipaddr variable that is defined like char *ipaddr

See my code below.

I tried with ipaddr = readdata [1], but ...

rgs

#include "settings.h"
#include<iostream>
#include<fstream>
#include<Windows.h>
#include <vector>
using namespace std;

int readfile ();





char *ipaddr;
string readdata;
namespace iocp {
SettingsData::SettingsData()

  :
  IOCP_Port(8092) {
	readfile ();
    hostAddress.s_addr = inet_addr(ipaddr);
}

SettingsData Settings;

}   // end namespace iocp





int readfile()
{

            ifstream stream1("D:\\file1.txt");
            char a[80];
            std::vector<std::string> readdata;
            if(!stream1)
            {
                        cout << "While opening a file an error is encountered" << endl;
            }
            else
            {
                       cout << "File is successfully opened" << endl;


            }
            while(!stream1.eof())
            {
                        stream1 >> a;
                        readdata.push_back(a); //now readdata is an array with everything read from the file //Sleep ( 1000);

            }
            return(0);
 }

[TheDestroyer]

Here's the question, why do you want to use char*? if you just want to pass it to a function, you can use the method of std::string::c_str(), which returns a const char* to your string, you can use it as a C-String to pass it to some function as well:

std::cout << readdata[1].c_str() << std::endl; //you're printing a c-string here 

Now if you want to copy it to a char* for some other purpose, use the strcpy:

#include <string.h>

char* mystring = new char[readdata[1].size() + 1]; // + 1 because you're converting to a null terminated character
strcpy(mystring, readdata[1].c_str()); //this copies your string to mystring 

I didn't test this code, it's just from the top of my head, so good luck :-)

[Cubbi]

Don't forget to replace

while(!stream1.eof())
{
    stream1 >> a;
   readdata.push_back(a);
}

with

while(stream1 >> a)
{
    readdata.push_back(a);
}

Because you used "while(!stream1.eof())", your loop actually attempts to read past the end of file and adds one extraneous element to readdata, an empty string.