public member function

std::istream::tellg

<istream>
streampos tellg ( );
Get position of the get pointer.
Returns the absolute position of the get pointer.

The get pointer determines the next location in the input sequence to be read by the next input operation.

Parameters

none

Return Value

An integral value of type streampos with the number of characters between the beginning of the input sequence and the current position.

Failure is indicated by returning a value of -1.

Example

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
 
// read a file into memory
#include <iostream>
#include <fstream>
using namespace std;

int main () {
  int length;
  char * buffer;

  ifstream is;
  is.open ("test.txt", ios::binary );

  // get length of file:
  is.seekg (0, ios::end);
  length = is.tellg();
  is.seekg (0, ios::beg);

  // allocate memory:
  buffer = new char [length];

  // read data as a block:
  is.read (buffer,length);

  is.close();

  cout.write (buffer,length);

  delete[] buffer;
  return 0;
}


In this example, tellg is used to get the position in the stream after it has been moved with seekg to the end of the stream, therefore determining the size of the file.

Basic template member declaration

(basic_istream<charT,traits>)
1
2
 
typedef traits::pos_type pos_type;
pos_type tellg ();


See also

istream::seekg
Set position of the get pointer (public member function)
ostream::tellp
Get position of put pointer (public member function)