_tell, _telli64
The latest version of this topic can be found at _tell, _telli64.
Get the position of the file pointer.
Syntax
long _tell(
int handle
);
__int64 _telli64(
int handle
);
Parameters
handle
File descriptor referring to open file.
Return Value
The current position of the file pointer. On devices incapable of seeking, the return value is undefined.
A return value of –1L indicates an error. If handle is an invalid file descriptor, the invalid parameter handler is invoked, as described in Parameter Validation. If execution is allowed to continue, these functions set errno to EBADF and return -1L.
See _doserrno, errno, _sys_errlist, and _sys_nerr for more information on this, and other, return codes.
Remarks
The _tell function gets the current position of the file pointer (if any) associated with the handle argument. The position is expressed as the number of bytes from the beginning of the file. For the _telli64 function, this value is expressed as a 64-bit integer.
Requirements
| Routine | Required header |
|---|---|
_tell, _telli64 |
<io.h> |
For additional compatibility information, see Compatibility in the Introduction.
Example
// crt_tell.c
// This program uses _tell to tell the
// file pointer position after a file read.
//
#include <io.h>
#include <stdio.h>
#include <fcntl.h>
#include <share.h>
#include <string.h>
int main( void )
{
int fh;
char buffer[500];
if ( _sopen_s( &fh, "crt_tell.txt", _O_RDONLY, _SH_DENYNO, 0) )
{
char buff[50];
_strerror_s( buff, sizeof(buff), NULL );
printf( buff );
exit( -1 );
}
if( _read( fh, buffer, 500 ) > 0 )
printf( "Current file position is: %d\n", _tell( fh ) );
_close( fh );
}
Input: crt_tell.txt
Line one.
Line two.
Output
Current file position is: 20