reading data from a file - link list

i would like to write a main for my class -> my problem is that i really have no idea how to read data from a file..
this is my class file ...

Code:

---


#include <iostream>
#include <cstdlib>
using namespace std;

struct node
{
  string IPaddress;
  int count;
  node *link;
};

class IPlist
{
  // contains an ordered list of IP addresses and a count of each
  // occurrence
  public:

    IPlist();  // default constructor
              // creates a new empty list

    ~IPlist(); // destructor - reallocates all dynamic memory of list

    IPlist (const IPlist & other);
              // copy constructor to create a deep copy of other IPlist
              // object

    bool empty() const;
              // precondition : none
              // postcondition : returns true if list is empty
              //                and otherwise false

    void insertInOrder(string address);
              // precondition : list is ordered and address is not in list
              // postcondition : list is ordered and contains address

    bool isPresent(string address) const;
              // precondition : none
              // postcondition : returns true if a node containing address
              //                is present in list and otherwise false

    void updateCount(string address);
              // precondition : address is in list
              // postcondition : the count of node with address has been incremented

    node *find (string address) const;
              // precondition : none
              // postcondition : returns a pointer to node containing address or
              //                NULL if not present

    void display() const;
              // precondition : none
              // postcondition : the list has been displayed
              // one record per line, tab-separated
              // with heading IPaddress Count
    private:
   
      node *list;
};

---

any idea will be really appreciated

this is my main code but got some error...

Code:

---


#include <iostream>
#include <cstdlib>
#include <fstream>

using namespace std;

int main()
{
        ifstream myFile;          //input file stream variable
    char filename[40];        //filename is used to store the name of the input file
   
   
    cout<<"Enter name of file : ";
    cin>>filename;
    myFile.open(filename); //open the input file
   
    while(myFile.fail()) //if open did not fail
    {
        cout << "Invalid file name" << endl;
        cout << "Enter name of file : " ; //read the name of the input file
        myFile.open(filename); //open the input file
    }
    while(!myFile.eof())
    {
        myFile>> filename;
        cout << filename << endl;
    }
   
    system("pause");
    return 0;
}

---

the content of the .txt file is

192.149.089.061

100.001.004.031

034.056.078.012

192.149.089.061
100.001.004.031

192.149.089.061

111.022.033.004

192.149.089.061

111.022.033.004

111.022.033.004

but after compile the program, the output is as below...

192.149.089.061

100.001.004.031

034.056.078.012

192.149.089.061
100.001.004.031

192.149.089.061

111.022.033.004

192.149.089.061

111.022.033.004

111.022.033.004

111.022.033.004

That's why they tell in the FAQ that it is not a good idea to test for EOF

Code:

---

while(myFile>> filename) {
        cout << filename << endl;
}

---

is the preferred solution.
Kurt
EDIT:

Code:

---

    while(myFile.fail()) //if open did not fail
    {
        cout << "Invalid file name" << endl;
        cout << "Enter name of file : " ; //read the name of the input file
        myFile.open(filename); //open the input file
    }

---

this while loop will not do what you expect it to do. Once a stream has failed it will not become good anymore unless you call clear() before open().

Quote:

---

Originally Posted by ZuK

That's why they tell in the FAQ that it is not a good idea to test for EOF

Code:

---

while(myFile>> filename) {
        cout << filename << endl;
}

---

is the preferred solution.
Kurt
EDIT:

Code:

---

    while(myFile.fail()) //if open did not fail
    {
        cout << "Invalid file name" << endl;
        cout << "Enter name of file : " ; //read the name of the input file
        myFile.open(filename); //open the input file
    }

---

this while loop will not do what you expect it to do. Once a stream has failed it will not become good anymore unless you call clear() before open().

---

is this wat you mean

Code:

---

    while(myFile.fail()) //if open did not fail
    {
        myFile.clear();
        cout << "Invalid file name" << endl;
        cout << "Enter name of file : " ; //read the name of the input file
        myFile.open(filename); //open the input file
    }

---

yes.

one more problem ...

Code:

---

    while(myFile.fail()) //if open did not fail
    {
      myFile.clear();
        cout << "Invalid file name" << endl;
        cout << "Enter name of file : " ; //read the name of the input file
        myFile.open(filename); //open the input file
    }

---

the problem is when the filename is incorrectly inserted or no such filename, the display keep looping, which display
Enter name of file : Invalid file name unstop

you have to input a new filname inside the loop.

Code:

---

    while(myFile.fail()) //if open did not fail
    {
      myFile.clear();
        cout << "Invalid file name" << endl;
        cout << "Enter name of file : " ; //read the name of the input file
      cin >> filename;
        myFile.open(filename); //open the input file
    }

---

opss... how could i miss that.. thank you anyway.. really appreciate the help although is a small problem .. cause i am really tired right now .. thank you dude...