$close(

)
 
======Technical:======
This function unbinds the given file descriptor (previously returned by
the $[[open]]() function) from the underlying file, causing the file to be
committed to disk if necessary.  An error is returned if it is passed a
file descriptor not produced by an $[[open]]() call.
 
======Practical:======
This function is used to close a file that was opened for reading or
writing by $[[open]]().  Data corruption may result if the client exits
before all open files are closed.
 
======Returns:======
<file>
-1   error
 0   file closed successfully