[PPT] - File Streams and File I/O http://cs.mst.edu Stream Operators PowerPoint Presentation

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File Streams and File I/O

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Stream Operators

Insertion Operator ‘<<’
As seen with cout << var
Extraction Operator ‘>>’
As seen with cin >> var

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Stream Declarations

#include <fstream> using namespace std; int main() { ifstream fin; // streams data from a file

fstream fout; // streams data to a file

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Stream Declarations

#include <fstream> using namespace std; int main() { ifstream fin(“input.dat”); //connects this stream // to an existing data // file in the same // directory

fstream fout(“output.dat”); //creates a text file

// in the same // directory

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Opening a File w/C-strings

#include <iostream> #include <fstream> using namespace std; int main() { ifstream fin;

fstream fout;

fin.open(“input.dat”); // !may not connect! fout.open(“output.dat”);

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Opening a File w/C-strings

#include <iostream> #include <fstream> using namespace std; int main() { ifstream fin;

fstream fout;

fin.open(“input.dat”); // !may not connect! fout.open(“output.dat”);

File may not exist
File may be misspelled
Perhaps wrong directory
etc

SLIDE 7

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Opening a File w/C-strings

#include <iostream> #include <fstream> using namespace std; int main() { char file[20]; ifstream fin; do { fin.clear(); cout << “enter name of file to connect to: “; cin.getline(file, 20); fin.open(file); } while(!fin);

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Opening a File w/C-strings

#include <iostream> #include <fstream> using namespace std; int main() { char file[20]; ifstream fin; do { fin.clear(); // clears the fail bit – allows retry cout << “enter name of file to connect to: “; cin.getline(file, 20); fin.open(file); } while(!fin);

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Opening a File w/C-strings

#include <iostream> #include <fstream> using namespace std; int main() { char file[20]; ifstream fin; do { fin.clear(); // clears the fail bit – allows retry cout << “enter name of file to connect to: “; cin.getline(file, 20); fin.open(file); } while(!fin);

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Opening a File w/C-strings

#include <iostream> #include <fstream> using namespace std; int main() { char file[20]; ifstream fin; do { fin.clear(); // clears the fail bit – allows retry cout << “enter name of file to connect to: “; cin.getline(file, 20); fin.open(file); } while(!fin);

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Opening a File w/C-strings

#include <iostream> #include <fstream> using namespace std; int main() { char file[20]; ifstream fin; do { fin.clear(); // clears the fail bit – allows retry cout << “enter name of file to connect to: “; cin.getline(file, 20); fin.open(file); } while(!fin);

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Opening a File w/std::strings

#include <iostream> #include <fstream> #include <string> using namespace std; int main() { string file; ifstream fin; do { fin.clear(); cout << “enter name of file to connect to: “; cin >> file; fin.open(file.c_str()); } while(!fin);

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Opening a File w/std::strings

#include <iostream> #include <fstream> #include <string> using namespace std; int main() { string file; ifstream fin; do { fin.clear(); cout << “enter name of file to connect to: “; cin >> file; fin.open(file.c_str()); } while(!fin);

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Opening a File w/std::strings

#include <iostream> #include <fstream> #include <string> using namespace std; int main() { string file; ifstream fin; do { fin.clear(); cout << “enter name of file to connect to: “; cin >> file; fin.open(file.c_str()); } while(!fin);

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Opening a File w/std::strings

#include <iostream> #include <fstream> #include <string> using namespace std; int main() { string file; ifstream fin; do { fin.clear(); cout << “enter name of file to connect to: “; cin >> file; fin.open(file.c_str()); } while(!fin);

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