Getting numbers from each line of a file

[tomtran3110]

I'm trying to get the numbers from every line of a file, each line has the same format:

A\tB\tC\tD

where A, B, C, D are the numbers that I want.

  ifstream database("path/file.txt");	
  string line;
  if(database.is_open()){
    while(getline(database, line)){
    }
  }
  database.close();

If I do it like this then what should I do with the line to separate all the number?

[jlb]

Since you have the line contained in a string you can use a stringstream to parse that string.

    while(getline(database, line)){
        stringstream sin(line);
        sin >> number1 >> number2 >> number3 >> number4;
    }

[tomtran3110]

Hi, jlb. I tried your suggestion with the following test code:

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

using namespace std;

int main(){
  ifstream database("file.txt");	
  string line;
  int A, B, C, D;
  if(database.is_open()){
    while(getline(database, line)){
      stringstream sin(line);
      sin >> A >> B >> C >> D;
    }
  }
  cout<<"A: "<<A<<endl<<"B: "<<B<<endl<<"C: "<<C<<endl<<"D: "<<D<<endl;
}

Well, after I compile, there is an error:

[Error] variable 'std::stringstream sin' has initializer but incomplete type

If I get anything wrong then would you please tell me, thank you in advance!

[Chervil]

[Error] variable 'std::stringstream sin' has initializer but incomplete type

You need to include the stringstream header

#include <sstream> 

[jlb]

Since you have this error did you find and study the documentation for the stringstream class? If you would've you should've seen that this class is defined in a header file. Did you try to include that required header file?

[tomtran3110]

Oops... I thought it was in the string header... Sorry for my stupidness...
But yet again, I have another problem now... The program has run...
Here is my "file.txt":

512\t604\t383\t565
898\t6558\t485\t1212
6541\t252\t4562\t156

And the output I get:

A: 6541
B: 0
C: 1992937936
D: 2752460

But the output I desire is:

A: 6541
B: 252
C: 4562
D: 156

Is "\t" a problem?

[Chervil]

Is "\t" a problem?

Yes. Inside a C++ program , use '\t' to represent a tab. But in the actual text file, just press the tab key to type a real tab.
file.txt

512	604	383	565
898	6558	485	1212
6541	252	4562	156

[jlb]

When I run the program I get your desired output.

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

using namespace std;

int main(){
  //ifstream database("file.txt");
  stringstream database("512\t604\t383\t565\n898\t6558\t485\t1212\n6541\t252\t4562\t156\n");

  string line;
  int A, B, C, D;

    while(getline(database, line)){
      stringstream sin(line);
      sin >> A >> B >> C >> D;
    }
  cout<<"A: "<<A<<endl<<"B: "<<B<<endl<<"C: "<<C<<endl<<"D: "<<D<<endl;
}

Output:

A: 6541
B: 252
C: 4562
D: 156

You may want to move your cout statement into the loop to possibly see where your problem begins.

[tomtran3110]

Problem solved. I replace "\t" in my text file with tab and it went well. Thank you for the help!!