fgetpos, fseek, fsetpos, ftell, rewind - reposition a
int fseek( FILE *stream, long offset, int whence);
long ftell( FILE *stream);
void rewind( FILE *stream);
int fgetpos( FILE *stream, fpos_t *pos);
int fsetpos( FILE *stream, fpos_t *pos);
The fseek function sets the file position indicator for
the stream pointed to by stream. The new position, mea
sured in bytes, is obtained by adding offset bytes to the
position specified by whence. If whence is set to
SEEK_SET, SEEK_CUR, or SEEK_END, the offset is relative to
the start of the file, the current position indicator, or
end-of-file, respectively. A successful call to the fseek
function clears the end-of-file indicator for the stream
and undoes any effects of the ungetc(3) function on the
The ftell function obtains the current value of the file
position indicator for the stream pointed to by stream.
The rewind function sets the file position indicator for
the stream pointed to by stream to the beginning of the
file. It is equivalent to:
(void)fseek(stream, 0L, SEEK_SET)
except that the error indicator for the stream is also
cleared (see clearerr(3)).
The fgetpos and fsetpos functions are alternate interfaces
equivalent to ftell and fseek (with whence set to
SEEK_SET), setting and storing the current value of the
file offset into or from the object referenced by pos. On
some non-UNIX systems an fpos_t object may be a complex
object and these routines may be the only way to portably
reposition a text stream.
The rewind function returns no value. Upon successful
completion, fgetpos, fseek, fsetpos return 0, and ftell
returns the current offset. Otherwise, -1 is returned and
the global variable errno is set to indicate the error.
EBADF The stream specified is not a seekable stream.
SEEK_END, or SEEK_CUR.
The function fgetpos, fseek, fsetpos, and ftell may also
fail and set errno for any of the errors specified for the
routines fflush(3), fstat(2), lseek(2), and malloc(3).
The fgetpos, fsetpos, fseek, ftell, and rewind functions
conform to ANSI X3.159-1989 (``ANSI C'').