ftell (Windows CE 5.0)
Developing an Application > Microsoft C Run-time Library for Windows CE > Run-time Library Reference
Gets the current position of a file pointer.
long ftell( FILE*stream);
Parameters
- stream
Target FILE structure.
Return Values
ftell returns the current file position.
The value returned by ftell might not reflect the physical byte offset for streams opened in text mode, because text mode causes carriage return–linefeed translation.
Use ftell with fseek to return to file locations correctly.
On error, ftell returns –1L.
On devices incapable of seeking (such as terminals and printers), or when stream does not refer to an open file, the return value is undefined.
Remarks
The ftell function gets the current position of the file pointer (if any) associated with stream. The position is expressed as an offset relative to the beginning of the stream.
When a file is opened for appending data, the current file position is determined by the last I/O operation, not by where the next write would occur. For example, if a file is opened for an append and the last operation was a read, the file position is the point where the next read operation would start, not where the next write would start.
When a file is opened for appending, the file position is moved to end of file before any write operation.
If no I/O operation has yet occurred on a file opened for appending, the file position is the beginning of the file.
In text mode, CTRL+Z is interpreted as an end-of-file character on input.
In files opened for reading/writing, fopen and all related routines check for a CTRL+Z at the end of the file and remove it if possible. This is done because using ftell and fseek to move within a file that ends with a CTRL+Z might cause ftell to behave improperly near the end of the file.
Example
/* FTELL.C: This program opens a file named FTELL.C
* for reading and tries to read 100 characters. It
* then uses ftell to determine the position of the
* file pointer and displays this position.
*/
#include <stdio.h>
FILE *stream;
void main( void )
{
long position;
char list[100];
if( (stream = fopen( "ftell.c", "rb" )) != NULL )
{
/* Move the pointer by reading data: */
fread( list, sizeof( char ), 100, stream );
/* Get position after read: */
position = ftell( stream );
printf( "Position after trying to read 100 bytes: %ld\n",
position );
fclose( stream );
}
}
Output
Position after trying to read 100 bytes: 100
Requirements
OS Versions: Windows CE 2.0 and later.
Header: stdlib.h.
Link Library: coredll.dll.
See Also
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