Question

I think I should begin by saying that I’ve just installed linux(debian) in my pc and have zero foreknowledge about doing things in linux. This problem is probably due to some really simple thing.

The relevant part of the code is similar to this:

ifstream stockNames("names.txt");

    while (!stockNames.eof())
    {
        string snline;
        getline(stockNames,snline);
        cout << snline << endl;
        .
        .
        .
    }

this should print the first line of the file ‘names.txt’. Instead it prints an empty line. And when I try to use snline as an input in another function I get the error ‘Segmentation Fault’. How should I modify my code to do this? Is there any difference in usage of the ifstream in linux? Cause in windows the code works just fine

---

I’ve written the simple code below

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

using namespace std;

int main(int argc, const char *argv[])
{
    string dos = "names.txt";
    ifstream stockNames(dos.c_str() );

    string snline;
    while (getline(stockNames,snline))
    {
       cout << snline << " ";

    }
    return 0;
}

content of names.txt is

ABC

DEFG

HBO

instead of showing those line, cout << snline produces nothing

---

One more update: I’ve written two more codes.

(1)

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

using namespace std;

int main(int argc, const char *argv[])
{
    cout << "program has initiated" << endl;

    ifstream stockNames("names.txt");

    if( !stockNames )
        cout << "unable to open" << endl;

    string snline;
    while (getline(stockNames,snline))
    {
        cout << snline << endl;

    }
    return 0;
}

Result is as I desired. First ‘program has initiated’, then ABC, DEFG, HBO in different lines. But when I change this part

        cout << snline << endl;

as

        cout << snline << " hey" << endl;

Then ABC DEFG HBO does not appear and instead the only output is ” hey”.

This is crazy, how can this be??

btw I tried to make a debug with ddd and when I check the variable snline, ddd prints the following line
(gdb) print snline
$2 = {static npos = 4294967295, _M_dataplus = {> = {<__gnu_cxx::new_allocator> = {}, }, _M_p = 0x804c1a4 “ABC\r”}}

new mini update: when I change the relevant line as “cout << snline << ” ” << endl;” what’s printed out is ‘ BC’ ‘ FGH’ ‘ BO’ in seperate lines. Why does << operator overwrites over snline??

Answer 1

You have a dos file which uses \r\n at the end of each line. Linux doesn’t recognise \r as part of the line ending so it gets included in the snline string. \r causes the next thing printed to appear at the beginning of the line so ” hey” overwrites the stock names you were expecting to see.

Try

cout << snline << " " << endl;

and you’ll see what I mean