C++ LANGUAGE FILE POSITION POINTERS

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C++ LANGUAGE FILE POSITION POINTERS

File Position Pointers 


Both istream and ostream provide member functions for 
repositioning the file-position pointer. These member 
functions are seekg ("seek get") for istream and seekp 
("seek put") for ostream. 

The argument to seekg and seekp normally is a long 
integer. A second argument can be specified to indicate 
the seek direction. The seek direction can be ios::beg 
(the default) for positioning relative to the beginning 
of a stream, ios::cur for positioning relative to the 
current position in a stream or ios::end for positioning 
relative to the end of a stream. 

The file-position pointer is an integer value that 
specifies the location in the file as a number of bytes 
from the file's starting location. Some examples of 
positioning the "get" file-position pointer are: 

// position to the nth byte of fileObject (assumes ios::beg) 
fileObject.seekg( n ); 
 
// position n bytes forward in fileObject 
fileObject.seekg( n, ios::cur ); 
 
// position n bytes back from end of fileObject 
fileObject.seekg( n, ios::end ); 
 
// position at end of fileObject 
fileObject.seekg( 0, ios::end );