Reading multiple data types to file

This is a discussion on Reading multiple data types to file within the C++ Programming forums, part of the General Programming Boards category; If got a problem for reading multiple data types to a file using operator>> and getline. Let say I've got ...

  1. #1
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    Reading multiple data types to file

    If got a problem for reading multiple data types to a file using operator>> and getline.

    Let say I've got the following code:
    Code:
    #include <iostream>
    #include <string>
    #include <fstream>
    using namespace std;
    
    int main()
    {
    	ofstream fout("testfile.txt");
    	string s = "Writing multiple data types to a file", t, u;
    	fout << s << '\n';
    	int i = 2, j;
    	fout << i << '\n';
    	fout << s << '\n';
    	fout.close();
    	
    	ifstream fin("testfile.txt");
    	getline(fin, t);
    	fin >> j;
    	getline(fin, u);
    	cout << t << endl << j << endl << u << endl;
    	
    	return 0;
    }
    The problem is that string u is emtpy and not the the content of s that it supposed to have.

  2. #2
    and the hat of wrongness Salem's Avatar
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    fin >> j; does NOT consume a newline, so it instead gets read by the following getline.

    Either
    - don't mix input methods (like cin and getline)
    - use cin.ignore() to skip unused (and unwanted) data.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  3. #3
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    Thanks for the information.

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