File Input & Output Lesson xx

File Input & OutputLesson xx

Objectives • Data Streams • Numeric Output • Numeric Input • Multiple Numeric Output • Multiple Numeric Input • Character Output • Character Input • String Output • String Input • Current Position Pointer

Streams • Input and output is accomplished via streams in C++. • A stream is a flow (movement) of data

Console I/O int a; cin >> a; cout << a;

Defining Other Streams //file I/O int a; fin >> a; fout << a; //console I/O int a; cin >> a; cout << a;

Numeric Output #include <fstream> using std::ofstream; int main() { ofstreamfout; fout.open("junk.dat"); int a = 17; fout << a; fout.close(); return 0; }

File Setup #include <fstream> using std::ofstream; int main() { ofstreamfout; fout.open("junk.dat"); int a = 17; fout << a; fout.close(); return 0; }

Writing Data to File #include <fstream> using std::ofstream; int main() { ofstreamfout; fout.open("junk.dat"); int a = 17; fout << a; fout.close(); return 0; }

Steps for Writing to a File Include the correct header files Set up a stream object Attach a file to the stream object Write to file using the stream object Close file

Numeric Input #include <fstream> using std::ifstream; int main() { ifstream fin; fin.open("junk.dat"); int a; fin >> a; fin.close(); return 0; }

ifstream Object #include <fstream> using std::ifstream; int main() { ifstream fin; fin.open("junk.dat"); int a; fin >> a; fin.close(); return 0; }

Read Number from File #include <fstream> using std::ifstream; int main() { ifstream fin; fin.open("junk.dat"); int a; fin >> a; fin.close(); return 0; }

Multiple Numeric Output #include <fstream> using std::ofstream; using std::endl; int main() { ofstreamfout; fout.open("junk.dat"); inti; for (i = 10; i < 110; i += 10) fout << i << endl; fout.close(); return 0; }

endl 10 20 30 40 50 60 70 80 90 100 102030405060708090100 fout << i << endl; fout << i ;

Multiple Numeric Input junk.dat #include <fstream> using std::ifstream; #include <iostream> using std::cout; int main() { ifstream fin; fin.open("junk.dat"); int a; while (fin >> a) cout << a << endl ; fin.close(); return 0; } 10 20 30 40 50 60 70 80 90 100

Character Output Part 1 #include <string> #include <fstream> using std::ofstream; #include <iostream> using std::cin; int main() { char ch; ofstreamfout; fout.open("test.dat"); while ( cin.get(ch) && (ch != '\n') ) fout.put(ch);

Character Output Part 2 char buf[] = "Feed a child fish & he eats for one day. Teach him to fish and he eats forever."; inti; for (i = 0; i < (int)strlen(buf); ++i) fout.put(buf[i]); fout.close(); return 0; }

Character Input #include <fstream> using std::ifstream; #include <iostream> using std::cout; int main() { char ch; ifstream fin; fin.open("test.dat"); while(fin.get(ch)) cout << ch; fin.close(); return 0; }

String Output Part 1 #include <fstream> using std::ofstream; using std::ios; #include <iostream> using std::cin; using std::endl; #include <string>

String Output Part 2 • int main() { char buf[80]; ofstreamfout; fout.open("test.dat"); • while(cin.getline(buf, 80) &&(strlen(buf) > 0)) fout << buf << endl;

String Output Part 3 fout << "Better to remain quiet\n"; fout << "and be thought a fool\n"; fout << "that to open one's mouth\n"; fout << "and erase all doubts.\n"; fout.close(); return 0; }

String Input #include <fstream> using std::ifstream; #include <iostream> using std::cout; using std::endl; int main() { char buf[80]; ifstream fin; fin.open("test.dat"); while(fin.getline(buf, 80)) cout << buf << endl; fin.close(); return 0; }

File Processing Commands fout << x; //write x to file fin >> x; //read data from file into x fout.put(ch); //write character in ch onto file fin.get (ch); //read 1 character from file into ch fout << “Kow\n"; //write a string onto file fin.getline(b, 80); //read a string into array b

Current Position Pointer (CP) junk.dat ifstream fin; fin.open("junk.dat"); int a; while (fin >> a) cout << a << endl ; CP 10 20 30 40 50 60 70 80 90 100

Current Position Pointer (CP) junk.dat ifstream fin; fin.open("junk.dat"); int a; while (fin >> a) cout << a << endl ; 10 20 30 40 50 60 70 80 90 100 CP

Summary • Data Stream • Numeric Output • Numeric Input • Multiple Numeric Output • Multiple Numeric Input • Character Output • Character Input • String Output • String Input • Current Position Pointer

File Input & Output Lesson xx