ftell Function

The ftell function is used to find the current position of a file pointer.

Stream

Pointer to an open FILE structure

>=0

Current number of bytes by which the file pointer is positioned from the origin..

-1

The seek failed.

#include <stdio.h> 
 .  .  .
  FILE *    Account_Master;
  char      Buffer [100];
  int       Maximum;
  int       Actual;
  long      Pos;
    .  .  .
  Maximum = 100;
    .  .  .
  Account_Master = open ("accounts.dat", "r");
    .  .  .
  while (!eof (Account_Master)) {
    Pos = ftell (Account_Master);
    Actual = read (Account_Master, Buffer, Maximum);
    .  .  .
    fseek (Account_Master, Pos, SEEK_SET);
    Actual = fwrite (Buffer, 1, Maximum, Account_Master);
    .  .  .
  }