Expert: Prince M. Premnath - 11/23/2006

Question

Write a statement that moves the get pointer 13 bytes backward from the current position in a stream object called f1.

thanks. .

Answer
Dear Rikin!

There are two member functions to move the file pointer to the desired location in a file
seekg(offset , refposition);
seekp(offset , refposition);

The parameter offset refer to the number of bytes th file pointer to be moved from the position referred by the parameter refposition  ,
the available constants for refposition are .
1. ios::beg     beginning of a file
2. ios::cur     from the current position of the pointer
3. ios::end     End of the file.

*The seekg() function associate with the file's 'get' pointer  , where as seekp() for file's put pointer

Here is the options allowed for seekg() function.

f1.seekg(0 , ios::beg);  moves pointer to the beginning
f1.seekg(0 , ios::cur);  stay current position
f1.seekg(0 , ios::end);  move to end
f1.seekg(n , ios::beg);  move(n+1) bytes from the beginning
f1.seekg(n , ios::cur);  moves n bytes forward from the current position
f1.seekg(-n , ios::cur);  moves n bytes backward from the current position
f1.seekg(-n, ios::end);  move n bytes backward from the end

* So inorder to move 13 bytes backward from the current position in a stream object called f1 you should have to use  the statement like this

f1.seekg(-13  , ios::cur);


Regards !
Prince M. Premnath
-Happy Programming.