The fseek function sets the file position indicator for the stream
pointed to by stream. The new position, measured 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 same stream.
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
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.