(PECL eio >= 0.0.1dev)
eio_truncate — Truncate a file
$path,$offset = 0,$pri = EIO_PRI_DEFAULT,$callback = NULL,$data = NULL
  eio_truncate() causes the regular file named by path to be truncated to
  a size of precisely length bytes
  
pathFile path
offsetOffset from beginning of the file.
priThe request priority: EIO_PRI_DEFAULT, EIO_PRI_MIN, EIO_PRI_MAX, or null.
If null passed, pri internally is set to
EIO_PRI_DEFAULT.
callback
callback function is called when the request is done.
It should match the following prototype: 
void callback(mixed $data, int $result[, resource $req]);
datais custom data passed to the request.
resultrequest-specific result value; basically, the value returned by corresponding system call.
reqis optional request resource which can be used with functions like eio_get_last_error()
data
     Arbitrary variable passed to callback.
     
   eio_busy() returns request resource on success, or false on failure.
  
