1. File Streams and File I/O

2. Stream Operators Insertion Operator ‘<<’
As seen with cout << var
Extraction Operator ‘>>’
As seen with cin >> var

3. Stream Declarations
#include <fstream> using namespace std; int main() { ifstream fin; // streams data from a file ofstream fout; // streams data to a file

4. 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 ofstream fout(“output.dat”); //creates a text file // in the same

5. Opening a File w/C-strings
#include <iostream> #include <fstream> using namespace std; int main() { ifstream fin; ofstream fout; fin.open(“input.dat”); // !may not connect! fout.open(“output.dat”);

6. Opening a File w/C-strings
#include <iostream> #include <fstream> using namespace std; int main() { ifstream fin; ofstream fout; fin.open(“input.dat”); // !may not connect! fout.open(“output.dat”);
File may not exist
File may be misspelled
Perhaps wrong directory
etc

7. 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);

8. 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);

9. 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);

10. 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);

11. 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);

12. 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);

13. 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);

14. 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);

15. 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);

16. Reading a File input.dat 3 -1 34 56 3 14 12 6 124
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { string file; ifstream fin; int num; ... // code for opening the file fin >> num; etc;
input.dat

17. Reading a File input.dat 3 -1 34 56 3 14 12 6 124
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { string file; ifstream fin; int num; ... // code for opening the file fin >> num; etc;
input.dat

18. Reading a File input.dat 3 -1 34 56 3 14 12 6 124
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { string file; ifstream fin; int num; ... // code for opening the file fin >> num; etc;
input.dat

19. Reading a File input.dat 3 -1 34 56 3 14 12 6 124
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { string file; ifstream fin; int num; ... // code for opening the file fin >> num; etc;
input.dat

20. Reading a File input.dat 3 -1 34 56 3 14 12 6 124
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { string file; ifstream fin; int num; ... // code for opening the file fin >> num; etc;
input.dat

21. Closing a File
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { string file; ifstream fin; int num; ... // code for opening the file ... // code for reading from the file fin.close();

22. More Reads input.dat Price Clayton 12 Hurson Ali 41 Buechler Matt 87
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file string last, first; int age; fin >> last; fin >> first; fin >> age; etc.
input.dat
Price Clayton 12
Hurson Ali 41
Buechler Matt 87

23. More Reads input.dat Price Clayton 12 Hurson Ali 41 Buechler Matt 87
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file string last, first; int age; fin >> last; fin >> first; fin >> age; etc.
input.dat
Price Clayton 12
Hurson Ali 41
Buechler Matt 87

24. More Reads input.dat Price Clayton 12 Hurson Ali 41 Buechler Matt 87
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file string last, first; int age; fin >> last; fin >> first; fin >> age; etc.
input.dat
Price Clayton 12
Hurson Ali 41
Buechler Matt 87

25. More Reads input.dat Price Clayton 12 Hurson Ali 41 Buechler Matt 87
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file string last, first; int age; fin >> last; fin >> first; fin >> age; etc.
input.dat
Price Clayton 12
Hurson Ali 41
Buechler Matt 87

26. More Reads input.dat Price Clayton 12 Hurson Ali 41 Buechler Matt 87
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file string last, first; int age; fin >> last; fin >> first; fin >> age; etc.
input.dat
Price Clayton 12
Hurson Ali 41
Buechler Matt 87

27. More Reads input.dat Price Clayton 12 Hurson Ali 41 Buechler Matt 87
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file string last, first; int age; fin >> last; fin >> first; fin >> age; etc.
input.dat
Price Clayton 12
Hurson Ali 41
Buechler Matt 87

28. More Reads input.dat Price Clayton 12 Hurson Ali 41 Buechler Matt 87
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file string last, first; int age; fin >> last; fin >> first; fin >> age; etc.
input.dat
Price Clayton 12
Hurson Ali 41
Buechler Matt 87

29. More Reads
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file int class_num, course; char section; string title;
input.dat
A Intro to Programming
B Intro to Programming
C Intro to Programming
A Discrete Mathematics
B Discrete Mathematics
A Data Structures
B Data Structures

30. More Reads
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file int class_num, course; char section; string title;
input.dat
A Intro to Programming
B Intro to Programming
C Intro to Programming
A Discrete Mathematics
B Discrete Mathematics
A Data Structures
B Data Structures

31. More Reads
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file int class_num, course; char section; string title;
input.dat
A Intro to Programming
B Intro to Programming
C Intro to Programming
A Discrete Mathematics
B Discrete Mathematics
A Data Structures
B Data Structures

32. More Reads
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file int class_num, course; char section; string title;
input.dat
A Intro to Programming
B Intro to Programming
C Intro to Programming
A Discrete Mathematics
B Discrete Mathematics
A Data Structures
B Data Structures

33. More Reads
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file int class_num, course; char section; string title; fin >> class_num; fin >> course; fin >> section; getline(fin, title, ‘\n’);
input.dat
A Intro to Programming
B Intro to Programming
C Intro to Programming
A Discrete Mathematics
B Discrete Mathematics
A Data Structures
B Data Structures

34. More Reads input.dat Price, Clayton Hurson, Ali Buechler, Matt
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { ... // code for opening the file string last, first; getline(fin, last, ‘,’); getline(fin, first, ‘\n’); etc.
input.dat
Price, Clayton
Hurson, Ali
Buechler, Matt
Van Horn, Keith
Walker, Betty Sue

35. End of Session