FILE I/O

C++

#include

So far, we have been using

the iostream standard library, which

provides cin and cout methods for reading

from standard input (key board) and writing to

standard output (screen) respectively.

#include

Read from and write to a file requires the

fstream library.

We will concern ourselves with text files only

in CIS 22A & B.

Three new types: ifstream, ofstream, fstream.

We will use only the first two. There are many

ways to do this – I have tried to pick an easy

path that parallels all languages.

File Output

# include

//Declare file pointer

ofstream fileOut;

//Open file

fileOut.open(". . . “);

//Redirect output to this object

fileOut << " Happy? “;

//Close file

fileOut.close();

File Input – opening the file

#include

//Declare pointer to file

ifstream fileIn;

fileIn.open(". . . “);

cout << fileIn.fail(); //interesting but not necessary

fileIn >> variable_of_your_choice;

getline( , ); //picks up the newline

File Input – part of GIGO Rule

if (fileIn.fail()) //Always check that it exists

{

cout << "No such file";

system("pause");

exit(100);

}

File Input – Simple redirection

fileIn >> variable_of_your_choice;

getline( , ); //picks up the newline

fileIn.get(ch); //where ch is type char

File Input – looping until end of file

int count = 0;

while(!inFile.eof())

{

inFile>> mlsNum;

fileIn >> price >> sqFt;

. . .

count++;

}

Passing a file to a function

//Input file

void getData(ifstream& myFile, . . .

//Output file

Void output(ofstream& fileOut, . . .