File I/O and Arrays

I have a text document namelist.txt
This file contains a list of names in this format:

Aimee
Alice
Alicia
Allison

etc.

Here's what I want to do.

-Open the file for reading
-Read the first line
-Assign the first line "Aimee" to variable[0]
-Read the second line
-Assign the second line "Alice" to variable[1]
-Continue until EOF.

Here's what I've written so far.

Code:

---

#include <iostream>
#include <fstream>

using namespace std;

int main()
{
  ifstream fin;               
  char c[11];
  char names[50][11];
  int i=0;
  fin.open("namelist.txt", ios::in);
 
  if(fin.fail())
  {
    cout << "Error: Unable to open namelist.txt\n";
    exit(1);
  }

  while(!fin.fail() && !fin.eof())
  {
//    cout << c <<endl;         
    fin.getline(c,11,'\n')>>names[i];
//    strcpy(names[i],c);
    ++i;
  }
 
  fin.close();             
  system("PAUSE");
  return(0);
}

---

The problem is the "++i" line. It assigns the value to names[0] just fine, but then on the next loop it crashes. I don't understand why this is happening. Maybe I'm going about this the wrong way. Any help would be appreciated.

Code:

---

fin.getline(c,11,'\n')>>names[i];

---

Huh? What does this line actually do [or what do you INTEND it to do?]

--
Mats

It goes to namelist.txt through fin and reads a line to c, the buffer being 11 characters and the delim being a new line. It then passes it to names[i]. It seems to work for the first time around when i=0, but once i is increased the app just crashes.

Quote:

---

Originally Posted by John Gaden

It goes to namelist.txt through fin and reads a line to c, the buffer being 11 characters and the delim being a new line. It then passes it to names[i]. It seems to work for the first time around when i=0, but once i is increased the app just crashes.

---

But that is certainly not what the code you have written actually does. I _THINK_ what it does is that it reads a string into c, it THEN reads another line of text into names[i]. This is because getline returns (a reference to) the istream that was passed into it.

I'm sure that's not what you want.

If you add a "cout << c << " " << names[i] << endl;" after this line, then you will probably see that c contains your first name and names[i] contains the second name in your list.

Also, you should not use eof to control the loop itself - it only gets set AFTER the input has tried to read past the end of file, which means that in most cases, you have one extra element in the input that is "uninitialized garbage". See the FAQ for discussion on this.

--
Mats

Thanks a lot. :)

I understand what you were saying about my >> idea.
Turns out strcpy was the correct way to go, the issue seemed that "names[50][11]" 50 was not enough. Stupid mistake.

This is the code that ended up working.

Code:

---

  while(!fin.fail())
  {     
    fin.getline(c,11,'\n');
    strcpy(names[i],c);
    cout<<names[i]<<endl;
    ++i;
  }

---

Quote:

---

Originally Posted by John Gaden

Thanks a lot. :)

I understand what you were saying about my >> idea.
Turns out strcpy was the correct way to go, the issue seemed that "names[50][11]" 50 was not enough. Stupid mistake.

---

ALWAYS check limits in loops.

--
Mats

It doesn't have to be that complicated. Something as simple as this would work.

Code:

---

  while(fin.getline(names[i],11,'\n'))
  {     
    cout<<names[i]<<endl;
    ++i;
  }

---

To satisfy matsp, you might want to add this expression to the while loop. :)

Code:

---

while(i < sizeof(names) / sizeof(*names) && fin.getline(names[i],11,'\n'))

---