Page 291 - DCAP404 _Object Oriented Programming

Object-oriented Programming

Notes for(int j=0; j<4;j++)
myfile.get(ch);
myfile.seekg(-2);
//this will take the pointer to 2 characters before the current
location. It will now point to (l)
seekp()

This function does to output files what seekp() does to input files. It shifts the pointer to the
specified location in the output file. If you want to overwrite the last 5 characters, you will have
to go back 5 characters from the current pointer position. This you can do by the following
statement.
myfile.seekp(-5);

ignore()

This function is used when reading a file to ignore certain number of characters. You can use
seekg() as well for this purpose just to move the pointer up in the file. However, ignore()
function has one advantage over seekg() function. The prototype is of ignore() function is given
below.

fstream& ignore( int, char);
Caution
You can specify a delimiter character in ignore() function whence it ignores all the characters up
to the first occurrence of the specified delimiter.
Where int is the count of characters to be ignored and delimiter is the character up to which you
would like to ignore as demonstrated in the following program.

//demonstration of ignore() function
#include <fstream.h>
void main()
{
//Assume that the text contained in data.dat file is “Welcome
to C++”
ifstream myfile(“data.dat”);
static char Carray[10];
//go on ignoring all the characters in the input up to 10th
character unless an ‘m’ is found

myfile.ignore(10,’m’);
myfile.read(Carray,10);
cout << Carray << endl; //it should display “me to C++”
myfile.close();
}

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