c++ adding numbers to each line

[redbull805]

Need some help, writing a program that will read the text from a file, but when it prints it out to the console each new line from the file should be numbered.
example
file1
a
b
c

console print out should be
1: a
2: b
3: c

and if a second files has more lines the code should be adding a new number each time.

I tried a few things but I can only get my code to print the same number if anyone can help let me know


#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>

using namespace std;

int main()
{
//variables
ifstream data_store;
string file_name;
string line;

//asks user to enter a name of a file
cout << "Enter filename" << endl;
//user will enter a name of a file.
cin >> file_name;

//open the file
data_store.open(file_name.c_str());


//loop for each line

while (!data_store.eof())
{
//print out lines from text files
getline(data_store, line);
cout << "1: "<< line << endl;
}
//close file
data_store.close();


return 0;
}

[cppbegin]

Edit:
Ahhh, getting tired... Should go for a sleep...
You could use the getline method of ifstream or you could add a counter to your while loop.
For reference check:
http://www.cplusplus.com/reference/fstream/ifstream/
As NT3 stated below

[TwilightSpectre]

In your print line, you have std::cout << "1: " << line << std::endl. When you add to the value, the line number doesn't change (i.e. its always 1). Instead, try something like this:

int i = 0;
while (!data_store.eof()) {
    std::getline(data_store, line);
    std::cout << ++i << ": " << line << std::endl;
}

What this does is it gets you a number "i", and adds one to it every time you loop through. This should give you the result you want.

[redbull805]

NT3 Thanks a lot that worked.

[Stewbond]

+1 NT3, that's exactly what I was thinking.

[JLBorges]

#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>

using namespace std;

int main()
{
    /*
    Prefer definiing variables close to the point of their first use

    //variables
    ifstream data_store;
    string file_name;
    string line;
    */

    string file_name;
    //asks user to enter a name of a file
    //cout << "Enter filename" << endl;
    cout << "Enter filename\n" ; // cout (tied to cin), is flushed before input
    //user will enter a name of a file.
    cin >> file_name;

    //open the file
    // data_store.open(file_name.c_str());
    // let the constructor open it for us
    ifstream data_store(file_name) ;

    // the line number is an integer
    int line_number = 0 ;
    // and the line is a string
    std::string line ;

    //loop for each line

    // while (!data_store.eof())
    // checking for failure before attempted input leads to a subtle error
    // {
    //      getline(data_store, line) ; // what happens if this fails?
    //      we don't check for failure and proceed as if we had successfully read a line
    //      ...
    // }


    while( getline(data_store, line) ) // this is canonical
    {
        //print out he line just read along with the line number
        cout << setw(4) // we expect at most 9999 lines
             << ++line_number // we print line numbers starting at one
             << ". "
             << line << /*endl*/ '\n' ; // there is no need to force a gratituos flush of cout
    }

    //close file
    // data_store.close();
    // the destructor will close it for us


    // return 0;
    // return 0 is implied when we reach the end of main()
}